Applied Mechanics doi: 10.3390/applmech7020042

Authors: Konstantin Manuel Prabitz Alexander Walzl Martin Stockinger

This study examines the deformation behaviour of laser powder bed fusion-produced A20X aluminium alloy and its accurate representation using flow curve models that account for die–specimen friction. Tests across multiple strain rates at room temperature were conducted on a Gleeble 3800; force–displacement data were friction-corrected to derive constitutive flow curves. A mathematical model was developed to capture barrelling and its impact on the stress–strain response, yielding corrected stresses significantly lower than measured values and validating the correction. An equation linking key post-deformation geometric parameters to their mathematical representation correlated well with a calibrated 2D finite element model, which reliably predicted plastic strain and deformation. The model’s friction factors agreed with experimental data, enabling efficient determination of the friction coefficient. Microstructural analysis and micrographs supported the predicted plastic strain distributions. Together, the corrected experiments and validated simulations provide a robust description of A20X’s response and inform performance and application potential.

Applied Mechanics doi: 10.3390/applmech7020041

Authors: Sherif Fakher

Oil and gas well cement is routinely exposed to aggressive chemical and mechanical environments that can compromise long-term zonal isolation. Conventional Portland cement systems, which rely on hydration products such as calcium silicate hydrate (C–S–H), are particularly vulnerable to acid attack, carbonation, high salinity, and thermal stress. This study investigates a polymer–mineral composite cement in which Class F fly ash is incorporated into an epoxy resin matrix at 0, 25, and 50 weight percent (wt%) loading. The composite samples were exposed for ten days to harsh downhole-representative environments, including hydrochloric acid (HCl, 15–28 wt%), sodium hydroxide (NaOH, 15–28 wt%), sodium chloride (NaCl) brines (20 wt%), crude oil, elevated temperatures up to 100 °C, and high-pressure carbon dioxide (CO2). Compressive strength was evaluated using a universal testing machine, capturing both deformation strength and ultimate failure strength to assess elastic and structural performance. Across most conditions, the composite maintained strengths exceeding 5000 psi, demonstrating strong chemical resistance. Acidic and CO2 exposures primarily reduced elastic deformation rather than ultimate strength, suggesting localized interaction with the polymer matrix. Elevated temperature reduced strength to ~2800 psi and diminished elasticity, marking the material’s upper thermal limit. Acetone exposure progressively degraded the polymer network, highlighting potential controlled removability. These findings indicate that embedding industrial fly ash in a polymer matrix produces a mechanically resilient and chemically robust cement alternative with up to 50 wt% industrial waste incorporation. This hybrid system offers a promising approach for wells exposed to acidic, CO2-rich, or high-salinity environments, where conventional Portland cement may fail.

Applied Mechanics doi: 10.3390/applmech7020040

Authors: Yuxuan Wang Chenlin Zhang Hao Liu Zhaohui Hu

To address high-dimensional coupling and extrapolation errors in vehicle lightweighting, this paper proposes a “Macroscopic Topology—Microscopic Data-Driven Size Synergy” methodology. Macroscopically, strain-energy-driven topology optimization on a simplified skeleton reduces mass by 9.4% (2835.8 kg to 2566.9 kg). Microscopically, a global ANOVA mechanism compresses 169 thickness variables to 39 core dimensions, mitigating the curse of dimensionality. Crucially, an active learning-based sequential approximate optimization (SAO) framework rectifies severe static model extrapolation errors (up to 475%) by injecting high-entropy boundary samples, boosting the R2 accuracy to near 0.90. Consequently, this approach secures the true Pareto solution, reducing full vehicle mass by 2.59% (to 6229.4 kg) while strictly adhering to EN12663 and EN15227 standards. This paradigm effectively resolves epistemic uncertainties, unlocking extreme lightweighting potential in complex systems.

Applied Mechanics doi: 10.3390/applmech7020039

Authors: Muhammad Umer Sohail Anees Waqar Muhammad Hammad Ajmal

This study presents a computational investigation of an ingenious Twain co-flow jet (CFJ) airfoil system featuring independently controlled micro-compressors for active flow control. Unlike conventional single-point or synchronously controlled CFJ configurations, the proposed system enables independent tuning of jet momentum coefficients at multiple locations along the airfoil surface. Reynolds-averaged Navier–Stokes (RANS) simulations are employed to analyze the impact of this independent control strategy on boundary layer behavior, lift enhancement, stall delay, and aerodynamic efficiency. The objective of this work is to establish a quantitative relationship between jet momentum distribution and aerodynamic performance, while also evaluating the associated energy consumption characteristics of the system. This technology works incredibly well at low speeds, significantly increasing stall angles and lift coefficients; at higher speeds, it uses less energy and improves the lift-to-drag ratio. Twain configuration offers more accurate control over pressure gradients, enabling adaptive performance during all flight phases. In this work, a Twain-compressor-integrated CFJ system is presented, in which jet momentum coefficients (Cμ = 0.05 and 0.1) are dynamically controlled by two independently controlled micro-compressors across various flight conditions (11.34 m/s, 138 m/s, 208 m/s). By optimizing injection at the leading edge and mid-chord—paired with synchronized suction at strategic withdrawal points—the system achieves precise boundary layer control with near-zero net mass flux. Modulating Cμ improves aerodynamic efficiency while limiting the total propulsion energy expenditure, allowing a smooth transition from high-lift takeoff to low-drag cruise, according to computational fluid dynamics (CFD) analysis. Due to these developments, Twain-compressor CFJ systems are now a scalable option for aircraft that need to be extremely aerodynamically versatile without sacrificing efficiency.

Applied Mechanics doi: 10.3390/applmech7020038

Authors: Masoud Ziaei

Despite their excellent torsional and bending strength, the economical production of hypotrochoidal profiles (H-profiles) remains an obstacle to their use. Due to the tool clearance angle, the commercially available twin-spindle turning process has limited ability to manufacture many of the profiles standardized according to DIN 3689 (Deutsches Institut für Normung). On the other hand, the manufacturing of cycloidal as a non-involute special geometry using generating processes (hobbing or continuous generating grinding) depends critically on the accuracy of the tool geometry—whether a hobbing cutter or a grinding worm. Conventional tool design methods—based on approximations, involute-derived profiles, or iterative trial-and-error corrections—face fundamental limitations: unpredictable cutting force variations, elevated surface roughness, and limited process capability. However, if the exact tool geometry has been determined analytically, the same machine achieves significantly better performance. In this work, the exact tool geometry conjugated to the H-profile for profile manufacturing is determined based on the gearing law. This provides modular H-profile manufacturing without deviations. Consequently, a design concept that enables the implementation of all existing rolling processes—including gear hobbing, gear shaping, gear planning, and other variants such as gear grinding—is presented. For profile shaping of hollow contours, the transfer ratio is considered and a curve conjugated to the profile contour is determined for the tool. A CAD-based simulation shows very good consistency with the analytically determined tool geometry.

Applied Mechanics doi: 10.3390/applmech7020037

Authors: Bassel Bakleh George Wardeh Hala Hasan Izabela Drygała Ali Jahami

Many existing reinforced concrete (RC) structures have undergone increases in service loads due to changes in use, functional upgrades, and evolving design codes. This highlights the need for reliable requalification methods that account for long-term degradation mechanisms, particularly those related to sustained loading and creep. This study investigates the residual flexural behavior of RC beams after long-term loading and evaluates its effects on stiffness and ultimate strength. Three RC beams were loaded to 43% of their short-term yielding moment and kept under sustained load for 210 days, while three identical specimens were maintained as unloaded references. Afterward, all beams were subjected to repeated four-point loading–unloading cycles to detect changes in stiffness, strength, and cyclic response. The results indicate that long-term loading did not significantly affect the beams’ ultimate load-carrying capacity compared with the reference specimens. However, the long-term-loaded beams exhibited a clear reduction in initial stiffness. This difference was most evident during the first loading cycle and gradually decreased in subsequent cycles. To interpret these findings, a layered fiber model was developed to simulate cyclic behavior while incorporating time-dependent concrete effects. The model successfully reproduced the main experimental trends, reinforcing the reliability of both the testing program and the analytical approach. The study enhances understanding of stiffness degradation in RC elements subjected to increased service loads.

Applied Mechanics doi: 10.3390/applmech7020036

Authors: Nikolaos M. Papadakis Georgios E. Stavroulakis

The present study investigates the influence of geometric parameters on the vibro-acoustic performance of piezoelectric speakers, with the objective of establishing quantitative design guidelines for resonance tuning and sound pressure level (SPL) enhancement. Understanding the dimension-dependent behavior of such devices is essential for the development of compact and efficient acoustic transducers. To this end, a fully coupled electromechanical–acoustic finite element model is developed in the frequency domain, incorporating linear piezoelectric constitutive relations, structural dynamics, and an external acoustic air domain. The model systematically examines the effects of variations in piezoelectric disc thickness, brass diaphragm thickness, and diaphragm radius. The results demonstrate that increasing the piezoelectric disc thickness leads to a noticeable increase in resonance frequency and a measurable enhancement in SPL due to strengthened electromechanical coupling. In contrast, reducing the brass membrane thickness primarily shifts the resonance frequency to lower values, while producing negligible changes in SPL amplitude. Furthermore, enlarging the diaphragm radius significantly decreases the fundamental resonance frequency, confirming its dominant influence on stiffness-controlled vibration behavior. These findings quantitatively establish the relationship between geometric design parameters and acoustic response, providing a predictive framework for performance optimization. The proposed modeling approach offers an effective and reliable tool for the design and refinement of high-performance piezoelectric speaker systems.

Applied Mechanics doi: 10.3390/applmech7020035

Authors: Foteini Konstandakopoulou George Hatzigeorgiou

This study investigates the nonlinear seismic response of elevated rectangular metallic silos subjected to sequential earthquake events, incorporating soil–structure interaction (SSI) and the influence of granular material fullness levels. Using three-dimensional (3D) finite element modeling and real seismic sequences recorded within short time windows, the study evaluates the effects of repeated earthquakes on maximum displacement, residual deformation and base shear. The analysis explicitly incorporates flexible elastic foundation systems to account for SSI effects, which significantly influence dynamic behavior. While considerable research exists on cylindrical silos, the seismic performance of rectangular configurations under multiple consecutive earthquakes remains poorly understood. The research systematically compares structural behavior and deformation patterns under single earthquake events versus multiple consecutive seismic sequences. The results demonstrate that consecutive seismic events produce significantly more severe structural responses than individual earthquake occurrences, with sequential earthquakes leading to amplified residual deformations (30–45% higher), increased stress concentrations in critical regions, and progressive degradation of structural capacity. These findings indicate that conventional single-event seismic design approaches may underestimate the vulnerability of rectangular silos in seismically active areas by approximately 30–40%, highlighting the critical importance of considering multiple-event scenarios in performance-based assessment and design procedures.

Applied Mechanics doi: 10.3390/applmech7020034

Authors: Maksat Temirkhan Ilyas Yessengabylov Assem Kyrykbayeva Azamat Kaliyev Sharaina Zholdassova Chingis Kharmyssov

This study presents a comparative investigation of MgCu intermetallic compounds, CuCoMnSn Heusler alloys, and carbon steel for spur gear applications using a novel tooth contact analysis (TCA) method. The TCA employs a nonlinear two-variable equation, providing a fast and accurate computational tool for evaluating gear contact behavior. By integrating material-specific elastic properties from density functional theory (DFT) studies, the analysis predicts contact paths, stress distributions, and responses to angular misalignments. Material selection strongly influences gear performance: MgCu is promising for lightweight applications, while CuCoMnSn is better suited where mechanical performance is prioritized. The CuCoMnSn alloy also exhibits half-metallic ferromagnetic behavior, offering potential functional advantages beyond mechanical performance. These results highlight the promise of intermetallics and Heusler alloys for high-performance, misalignment-tolerant gears and demonstrate the effectiveness of combining DFT-informed material modeling with the novel TCA method for optimized spur gear design.

Applied Mechanics doi: 10.3390/applmech7020033

Authors: Malati Mazumder Mahtab U. Ahmmed Md. Mamun Molla Md Farhad Hasan Sheikh Hassan

Hybrid nanofluids possess exceptional thermal conductivity, but one of the major concerns with nanoparticles is agglomeration. While the usage of surfactants or dispersants can be used to mitigate this issue, numerical investigation and sensitivity analyses can be more affordable when attempting to optimize and design a thermal device. The consideration of thermal radiation with conductive and convective heat transfer and appropriate nanoparticles may provide a greater solution without compromising the efficacy of hybrid nanofluids. In the present work, the concept of magnetohydrodynamics (MHD) is used to examine the impact of thermal radiation on a stable, two-dimensional, incompressible hybrid fluid consisting of nanoparticles (MWNCT)-Fe3O4 and water flowing over a vertical surface. The flow is governed by established equations of fluid dynamics, which use the Rosseland diffusion model to incorporate radiation effects. The implicit finite difference (IFD) was used to solve the mathematical equations. Sensitivity analyses were conducted as functions of volume fraction, radiation and magnetic variables. This study also examines the streamlines and isotherm lines with respect to the volume fraction, radiation parameter and magnetic parameter of the heat source. The results indicate that for a fixed radiation parameter, increasing the nanoparticle volume fraction by up to 20% leads to a reduction of approximately 37% in the skin friction coefficient, while the corresponding Nusselt number increases by nearly 50%. Furthermore, the introduction of a magnetic field parameter significantly suppresses wall shear stress and modifies the thermal boundary layer thickness, demonstrating the competing interaction between Lorentz-force-induced momentum damping and radiation-enhanced thermal diffusion. These quantified trends highlight the sensitivity of coupled momentum and heat transport to combined magnetic and radiative effects in hybrid nanofluid systems.

Applied Mechanics doi: 10.3390/applmech7020032

Authors: Thathsarani D. H. Herath Mudiyanselage Manjriker Gunaratne Andrés E. Tejada-Martínez

Most computational studies of vehicle hydroplaning have emphasized structural realism through fluid–structure interaction, tire deformation, tread geometry, and pavement surface characterization. By contrast, the hydrodynamics governing the flow in the tire vicinity, particularly the role of turbulence, have received comparatively limited attention. In a significant number of studies, the flow has been treated as laminar despite turbulent flow conditions, while in a few other studies turbulence modeling has been adopted without an explicit assessment of its impact on hydroplaning predictions. In this study, we present a simplified three-dimensional computational fluid dynamics (CFD) model designed to isolate the flow regimes governing hydroplaning and to quantify the mean effect of the turbulence modeling on the predicted hydroplaning speed. Using a finite-volume formulation with a volume-of-fluid representation of the air–water interface, the flow around and beneath a smooth 0.7 m-diameter tire sliding in locked-wheel mode over a flooded, nominally smooth pavement is simulated. The tire is represented as a rigid body with an idealized rectangular bottom patch whose area is determined from the tire load and inflation pressure, avoiding the need to prescribe a measured or assumed deformed footprint. Steady-state hydroplaning is modeled for a uniform upstream water film thickness of 7.62 mm with a 0.5 mm gap between the tire and the pavement, over tire inflation pressures ranging from approximately 100 to 300 kPa, and predictions are verified against the empirical NASA hydroplaning equation. For these conditions, simulations without turbulence closure exhibit a consistent, systematic underprediction of the hydroplaning speed of approximately 13.5% relative to the NASA relation. Incorporating turbulence effects through Reynolds-averaged closures substantially reduces this bias, with average deviations of about 6% for the realizable k–ε model and 2.4% for the shear stress transport (SST) k–ω model. An analysis of the results indicates that hydrodynamic lift is dominated by pressure buildup associated with stagnation at the lower leading edge of the tire, with a significant contribution from shear-dominated flow in the thin under-tire gap, and that turbulence acts to moderate the integrated lift from these pressure fields. These results demonstrate that explicitly accounting for turbulence in the tire vicinity is essential for reproducing empirical hydroplaning trends and for avoiding systematic bias in CFD-based hydroplaning predictions.

Applied Mechanics doi: 10.3390/applmech7020031

Authors: Biljana Mladenović Stepa Paunović Andrija Zorić Žarko Petrović Bojan Milošević

In structural engineering practice, the problem of thick plate bending occurs in designing shelters, foundations of high-rise buildings, counter-slabs, etc. In such cases, neglecting shear deformation can lead to significant errors in predicted behavior, especially when a plate is subjected to a concentrated force. In practice, neither a fully clamped nor an ideal simple support can be achieved during construction, so the plates are partially clamped, and this also applies to thick plates. Bending of thick rectangular plates with partially clamped edges has not been studied in the literature, so this paper addresses this issue. A comprehensive numerical analysis using a developed simple analytical model in the form of a Lévy-type solution based on Reissner theory has been carried out. The presented model is able to account for different degrees of rotational restraint in plates with two opposite edges simply supported and the other two partially clamped by introducing the fixity factor. The obtained results are compared with those available in the literature, as well as with a numerical FEM model, whereby good agreement is observed. The significant difference when using the proposed model to analyze a thick plate, as opposed to the models based on Kirchhoff theory, is underlined.

Applied Mechanics doi: 10.3390/applmech7020030

Authors: Qamar Maqbool Rashid Naseer Imran Akhtar

This study investigates the mechanisms of nonlinear modal interactions in a circularly curved cantilever beam, utilizing the geometrically exact Timoshenko beam formulation. The governing equations take into account shear deformation, rotary inertia, and the geometric nonlinearities associated with significant deflections. A Chebyshev pseudospectral scheme is employed to achieve highly accurate linear eigenvalues, which are subsequently used in a nonlinear modal projection to develop a reduced-order model. Explicit expressions for the quadratic and cubic modal coupling coefficients are derived. The Harmonic Balance Method is then applied to explore internal resonance phenomena, frequency modulation behavior, and the transfer of energy between non-commensurate lateral and normal vibration modes.

Applied Mechanics doi: 10.3390/applmech7020029

Authors: Fernando Jorge Mendes de Sousa José Renato Mendes de Sousa

In recent years, the discovery of new ultra-deepwater reservoirs has significantly increased both the importance and the complexity of offshore oil production. One of the main challenges in qualifying structures to operate under such severe conditions is the fatigue limit state, particularly fatigue induced by ocean waves. Wave-induced fatigue remains, both at the design stage and during the operation of flexible risers, one of the most demanding issues for engineers responsible for ensuring their structural integrity. This study presents a state-of-the-art review of wave-induced fatigue analysis in flexible risers. It includes a brief historical overview of the problem, a summary of the fatigue assessment methodologies traditionally adopted in offshore engineering, a discussion of pioneering contributions to stress calculation, and an overview of the main research trends currently being pursued. These trends reflect emerging challenges related to fatigue life prediction, including the high computational cost of time-domain analyses, the presence of elevated contaminant levels in transported fluids, the development of new materials to reduce loads or enhance resistance to aggressive environments, and the assessment of remaining service life in the presence of damaged or corroded tensile wires. The potential use of monitored data to reduce uncertainties in numerical modelling is also addressed. Despite the challenges discussed, the main conclusion of this work is that ongoing technological developments are expected to ensure that flexible risers remain key components of offshore oil and gas production systems.

Applied Mechanics doi: 10.3390/applmech7020028

Authors: North Yates Fernando Ponta Joshua Reese Alayna Farrell

Since the inception of utility-scale wind turbines, there has been a continual increase in the size of the devices used. One drawback of turbine size increase is that the weight of the rotor blades has grown dramatically. Technological advancements have allowed for the creation of light blades to overcome this issue. These lighter rotors are also less stiff than their predecessors and prone to experiencing aeroelastic vibrations that can lead to fatigue damage. Aerodynamic damping occurring during blade vibration has the potential to mitigate those oscillations; thus, understanding its underlying physics provides an extremely useful tool for future blade design. In a series of previous publications, the authors presented a novel reduced-order characterization technique for the oscillatory response of wind turbines, which allows for the analysis of rotor vibrations when excited by wind gust pulses. In this paper, the authors will apply the same gust pulse technique to analyze the physics of blade’s aerodynamic damping, identifying two physical mechanisms. The first acts either as a damper, or as an energy feeder, depending on operational conditions. The second operates in a purely dissipative manner. Results of numerical experiments on several operational scenarios illustrating these behavioral responses will be presented and discussed.

Applied Mechanics doi: 10.3390/applmech7020027

Authors: Jing Zhang Miao Yu Chuang Shi Qiying Li Ruipeng Li Hongwei Guo Rongqiang Liu

Space-deployable antennas have development requirements of an ultra-large aperture, high stiffness, and multi-frequency multiplexing. To address the challenge of stiffness characterization in the multi-closed-loop complex systems of deployable mechanisms, this paper proposes a parametric stiffness modeling method and a static stiffness model is established, ranging from components and limbs to the overall mechanism. The motion/force mapping model of the deployable mechanism is obtained using screw theory, and the stiffness mapping from joint space to workspace is achieved via the Jacobian matrix. A comprehensive stiffness model of the deployable mechanism incorporating joint effects is established based on the principle of virtual work and the superposition principle of deformations, and its validity is verified through finite element simulation. Building on this, stiffness characteristics based on structural configuration are investigated, and structural forms with excellent stiffness performance are selected through comprehensive evaluation. Six configurations of the deployable mechanism are derived topologically from this structure, and the optimal configuration is selected based on stiffness performance. The parametric stiffness modeling method proposed in this study can effectively characterize the contribution of each component to the overall system stiffness. It lays a theoretical foundation for establishing a quantitative relationship between stiffness performance and configuration, enabling performance-based configuration optimization and dimensional optimization.

Applied Mechanics doi: 10.3390/applmech7020026

Authors: Vladimir Kodnyanko

This paper presents the results of a study of the dynamic performance of an aerostatic thrust bearing with a microgroove and simple diaphragms. The objective of this study was to determine the influence of the lubrication gap thickness and the volume of the microgroove and pockets on the structural dynamics. Unlike most studies that typically use the second-order harmonic oscillator equation as the characteristic equation, the root criteria are determined with high accuracy when the characteristic equation is of an order no lower than the fourth order. The presented formulas allow one to find the optimal calculated dimensional gap, microgroove and pocket volume in terms of the best dynamic performance. For a well-damped thrust bearing, the required response speed and sufficient stability margin can only be achieved within a narrow range of 1–2 times the bearing gap volume. Calculations have shown that to ensure satisfactory thrust bearing dynamics, the calculated gap should not exceed 10–15 µm.

Applied Mechanics doi: 10.3390/applmech7010025

Authors: Sheldon Wang Clayton Brasher Jimmy Tran Pavle Kalaba Ty Criss

A sucker rod pump is an artificial lift system widely used in oil wells to extract crude oil from deep underground. Due to the clearance between the barrel and the pump plunger, a phenomenon termed slippage occurs in which the annulus column of oil returns to the pump chamber due to the plunger motion and the pressure difference at the two ends of the plunger. Although it is important to maintain the clearance for lubrication between the plunger and the pump barrel in order to prevent excessive wear and tear along with galling, excessive clearance can also be a primary factor in the reduction of oil well production and must be managed. In this research, after briefly reviewing the Couette and Poiseuille flows within the annulus region, the relaxation time for the transients, and the eccentricity effects, we focus on the derivation of important system parameters such the effective mass, stiffness, and damping ratio based on the measurements of the sucker rod displacement and the pressures or loads. Analysis of experimental measurement data can provide better understanding of the sucker rod pump system parameters, helping to quantify and manage the so-called slippage issues.

Applied Mechanics doi: 10.3390/applmech7010024

Authors: Eduardo Alcantara-Rojas Boris Miguel López-Rebollar Jesús Ramiro Félix-Félix Martha Fernanda Mohedano-Castillo Carlos Roberto Fonseca Ortiz Gerardo Cano-Perea

Wind energy has become an essential resource for the development and diversification of the energy sector in México and worldwide. In this context, the mechanical design of turbine blades has emerged as a priority research topic, given its impact on performance and viability. The present research evaluates the aero-structural response of multiple lay-up configurations of a 6 m blade by coupling computational fluid dynamics (CFD) and finite element analysis (FEA). The fluid–structure interaction (FSI) was simulated in ANSYS, a commercial software chosen for its capacity for multivariable analysis. The nominal operating conditions included a wind speed of 10.5 m/s and a rotational speed of 100 rpm, leading to a theoretical power output of 6591 W. For the proposed lay-up configurations, the Tsai-Wu and Puck (Global IRF) criteria were estimated and remained below the critical threshold of 1.0, indicating no risk of structural failure. However, some carbon fiber/epoxy layers, including unidirectional layers in the spar caps and bidirectional layers in the structural shear web, may present failure risks under extreme loading conditions. This applies to configurations with the lowest number of layers in the mid-span spar caps; this fact is reinforced by the main effects analysis. The results emphasize the relevance of conducting comprehensive composite failure evaluations to optimize material selection and structural design, even for small-scale blades.

Applied Mechanics doi: 10.3390/applmech7010023

Authors: S. M. Anas Rayeh Nasr Al-Dala’ien Mohammed Benzerara Mohammed Jalal Al-Ezzi

In many densely populated towns and semi-urban areas, masonry buildings often stand close to busy roads, exposing them to blasts from improvised explosives or other localized sources. Such structures are rarely designed to resist sudden explosive forces, making severe damage or even progressive collapse likely. Even moderate-intensity blasts can weaken walls, endanger occupants, and cause significant property loss. Unlike reinforced concrete, masonry is highly susceptible to explosive impact. Therefore, understanding how these buildings behave under blast loads and developing affordable protection methods is crucial. Low-rise unreinforced masonry (URM) structures, usually up to about 13 m in height (roughly 2–4 stories), common in villages, semi-urban regions, and conflict-prone zones, are particularly at risk. In many areas, these poorly constructed buildings lack proper engineering design and are therefore highly vulnerable to blast damage. Non-load-bearing internal dividers and perimeter enclosures are especially prone to lateral displacement, which can initiate instability and, in severe cases, lead to overall structural failure. This research focuses on reducing catastrophic damage in URM walls when exposed to close-proximity blast forces using concrete-based protective coatings, both with and without embedded steel-welded wire mesh. The study references a previously tested laterally supported clay brick wall built with cement–sand mortar as the baseline model, with its behavior validated against experimental findings from existing literature. Two blast cases were considered corresponding to scaled stand-off distances of 2.19 m/kg1/3 and 1.83 m/kg1/3, representing moderate flexural-shear cracking and full structural failure, respectively. To replicate the observed behavior, a comprehensive 3D numerical simulation was developed using the ABAQUS/Explicit 2020 solver. The model’s predictions were benchmarked and verified through comparison with reported test data. While both blast intensities were used to confirm computational accuracy, the effectiveness of UHPC and UHPFRC protective coatings with and without embedded wire mesh was specifically evaluated under the more severe collapse scenario (Z = 1.83 m/kg1/3). Results indicated that at a scaled distance of 1.83 m/kg1/3, the uncoated URM wall could not withstand the blast because of poor tensile and bending capacity. In contrast, the UHPC- and UHPFRC-coatings provided improved confinement and better stress distribution. When welded wire mesh was embedded, crack control improved further, the interface bond strengthened, and a larger portion of blast energy was absorbed and dissipated.

Applied Mechanics doi: 10.3390/applmech7010022

Authors: Bhagyashri Bachhav Dawei Zhang Hanghang Gao Hauke Schmidt Chen Gang Songyun Ma Franz Bamer Bernd Markert

Fatigue failure constitutes an issue that cannot be ignored when designing welded steel structures due to the initiation of cracks at weld toes and defects under cyclic loading conditions. Traditional methods, such as the notch stress approach, estimate fatigue life by modeling local stress distributions using idealized weld geometries. While these methods are widely accepted in design codes, they can be limited by complexity and reduced accuracy in real-world applications. This study explores the use of artificial neural networks (ANNs) to enhance fatigue life prediction through data-driven modeling. The proposed method involves training an ANN using synthetic data generated through finite element simulations of S355 steel weldments under various loading histories, rates, and frequencies. The objective is to capture the influence of local geometric and stress features without relying solely on assumptions used in conventional approaches. The FEM-based training data incorporate both classical experimental findings and validated modeling practices. While performance evaluation of the ANN model is reserved for future work, this study lays the groundwork for replacing or supplementing the notch stress approach with a more adaptable and efficient predictive tool. The integration of machine learning into fatigue assessment has the potential to improve reliability, reduce computational burden, and support more informed maintenance and design decisions.

Applied Mechanics doi: 10.3390/applmech7010021

Authors: Raed Hossain Tanvir Ahmad Mohammed Aksir Talukder Md Mazedur Rahman Gyula Varga Saiaf Bin Rayhan

This study proposes two novel stiffened panel configurations, designated X and X-30, manufactured from the conventional aerospace alloy Al 2024-T3 to enhance the critical buckling resistance under in-plane compression. Their performance was evaluated against traditional T-, I-, L-, and Omega-type stiffeners, as well as a newly introduced Y-panel found in the literature. Initial results show that both proposed designs achieve 80–200% higher buckling capacity than conventional panels, with only a 4.54% difference between the X and X-30 configurations. A weight-constrained optimization was then conducted using a Box–Behnken design of experiments combined with a multi-objective genetic algorithm in Ansys DesignXplorer. After correcting inconsistencies in the initial optimization ranges, the prediction error in the optimized buckling values was reduced to 4%. The optimized X panel attained the highest critical buckling load of 2920 kN, followed by the X-30 panel with 2744.3 kN, corresponding to a 114–258% improvement over traditional stiffener geometries. A Pearson correlation matrix further suggested that, for all the stiffened panels except Omega, the base plate showed a strong correlation with the critical buckling load, typically ranging from 0.83 to 0.99. In contrast, for the X-30 panel, the lower base part also showed a strong correlation of 0.93.

Applied Mechanics doi: 10.3390/applmech7010020

Authors: C. Bhargavi K. S. Sreekeshava Manish S. Dharek B. K. Raghu Prasad J. V. Raghavendra

This study evaluates bamboo–coir hybrid composite panels developed for formwork applications using an 80:20 fiber–matrix ratio and a 50:50 bamboo-to-coir distribution. The novelty of this study lies in the combined assessment of formwork-relevant mechanical performance, Mode I and Mode II fracture behavior, finite element validation and post-fracture microstructural correlation for a high fiber volume fraction natural fiber hybrid panel. Mechanical, durability, fracture, numerical and microstructural investigations were performed and benchmarked against 10 mm thick construction-grade plywood. The hybrid panels exhibited a density of 805 ± 10.84 kg/m3, which is within 0.7% of plywood, a tensile strength of 50.20 ± 2.85 MPa, representing an increase of 41.8% over plywood, and a flexural strength of 38.60 ± 2.10 MPa, corresponding to an increase of 12.9% as compared to plywood. The impact energy absorption of hybrid panels was 7.85 ± 0.62 J, which is 26.6% greater than plywood. Mode I fracture testing yielded a fracture toughness of 456.65 ± 15.42 J/m2, corresponding to an increase of 9.3% over plywood, while Mode II fracture toughness yielded a value of 792.42 ± 30.18 J/m2, representing an increase of 13.7% over plywood. Finite element predictions deviated from experimental load–displacement responses by 5–13%. SEM observations identified fiber bridging, fiber pullout and interfacial sliding in the hybrid panels, consistent with the measured fracture energy values. The results indicate that bamboo–coir hybrid panels satisfy the mechanical and fracture performance requirements for reusable formwork systems.

Applied Mechanics doi: 10.3390/applmech7010019

Authors: Monica Ciminello Vittorio Memmolo Assunta Sorrentino Fulvio Romano

This paper presents the structural health monitoring (SHM) system applied to a 9 m composite outer wing box (OWB) specifically designed for a brand-new regional aircraft to detect barely visible impact damage (BVID) based on structural response data. The approach relies on different technologies to offer multilevel diagnosis, including impact detection as well as disbonding identification, localization, and sizing. The use of different sensing techniques based on piezoelectric transducers and distributed fiber optic sensors deployed all over wing structures is explored. Different features are simultaneously extracted from the propagating waves and from light scattering, able to detect low-energy BVID impact. In addition, the combined use of static and dynamic interrogation allows the estimation of the delamination surface after impact with good accuracy. The final test results on the OWB provided effectiveness in detecting, localizing, and tracking impact damage in the composite structure, ensuring long-term reliability and safety, as well as characterizing barely visible damage by a fully integrated onboard SHM system.

Applied Mechanics doi: 10.3390/applmech7010018

Authors: Abdelkader Hassein-Bey Nadir Belgroune Assia Bessi Omar Kebour Mohamed Mohammedi Ahmed Rafik Touil Amel Boudjemaa

This work reports the elaboration and testing of polydimethylsiloxane/titanium dioxide (PDMS/TiO2) polymer nanocomposites, focusing on producing and combining TiO2 nanoparticles with a polymer matrix through an ex situ route. By mixing the inherent flexibility of PDMS with the unique properties of nanoparticles, the nanocomposites aim to enhance mechanical stability, optical response, and photocatalytic activity. X-ray diffraction (XRD) confirmed the successful incorporation of TiO2 into the PDMS matrix. UV–visible spectroscopy monitored photocatalytic performance using metronidazole as a model pollutant under 365 nm irradiation. Kinetic analysis revealed degradation and showed that the reaction rate constant (k) increased with TiO2 loading, reaching a maximum of 0.0019 min−1 for the 6 wt.% composite. These findings indicate that while the reaction kinetics are slower than those of free powders, the PDMS/TiO2 nanocomposites provide a viable, recoverable, and flexible solution for environmental remediation applications. Future efforts will target improved durability, broadened visible light absorption, and process optimization for scalable fabrication.

Applied Mechanics doi: 10.3390/applmech7010017

Authors: Milad Kazemian Aleksandr Cherniaev

Non-crimp fabric (NCF) composites are increasingly adopted for structural components due to their high mechanical performance and processability. Like other fibre-reinforced plastics, NCFs remain vulnerable to in-service damage from tool drops or unintended collisions, which can substantially reduce load-bearing capacity. This study aimed to develop a validated numerical model capable of simulating damage initiation and post-impact behaviour through an integrated experimental–numerical approach. The mechanical properties of a representative unidirectional NCF composite were first experimentally established. Then, tubular NCF subcomponents were fabricated and tested under a two-phase loading protocol. In the first phase, damage was introduced using quasi-static indentation or controlled low-velocity impact. In the second phase, the residual load-bearing capacity of the damaged subcomponents was assessed under four-point bending. To support the research objective, a finite element model was developed in LS-DYNA to simulate both phases, using the MAT_ENHANCED_COMPOSITE_DAMAGE (MAT54) material formulation. Non-measurable input parameters, including stress limit factors and erosion strain thresholds, were calibrated via parameter estimation, sensitivity analysis, and iterative refinement. The final model showed close agreement with experiments in predicted damage location, deformation mode, and residual strength. X-ray computed tomography was used to validate delamination predictions. The findings support the development of reliable and cost-effective numerical tools for damage assessment in advanced composite structures.

Applied Mechanics doi: 10.3390/applmech7010016

Authors: Omar Kebour Rabah Magraoui Nadir Belgroune

The dynamic behavior of the DS306 detacher, a critical component in industrial fiber processing lines, plays a decisive role in maintenance performance and overall operational reliability. This study introduces a strengthened preventive maintenance strategy that leverages vibration analysis and dynamic modeling with a strong emphasis on early fault anticipation. A detailed numerical finite element model of the detacher was developed to determine its natural frequencies, critical modes, and dynamic response under real operating conditions. Experimental vibration measurements were conducted to validate the numerical model and identify characteristic frequencies associated with imbalance and wear. The results show that the proposed predictive framework not only reproduces the machine’s dynamic behavior with high accuracy but also anticipates mechanical degradation trends well before the occurrence of critical failures. This early-warning capability allows maintenance teams to plan interventions proactively, significantly reducing unexpected downtime, avoiding cascading damage, and improving long-term equipment availability. Overall, the study provides a robust and practical methodology for dynamic diagnosis, fault prediction, and optimized preventive maintenance in industrial rotating machinery.

Applied Mechanics doi: 10.3390/applmech7010015

Authors: Piotr Klejment

The Discrete Element Method is widely used in applied mechanics, particularly in situations where material continuity breaks down (fracturing, crushing, friction, granular flow) and classical rheological models fail (phase transition between solid and granular). In this study, the Discrete Element Method was employed to simulate stick–slip cycles, i.e., numerical earthquakes. At 2000 selected, regularly spaced time checkpoints, parameters describing the average state of all particles forming the numerical fault were recorded. These parameters were related to the average velocity of the particles and were treated as the numerical equivalent of (pseudo) Acoustic Emission. The collected datasets were used to train the Random Forest and Deep Learning models that successfully predicted the time to failure. SHapley Additive exPlanations (SHAP) was used to quantify the contribution of individual physical parameters of the particles to the prediction results. The main novelty of this study was the prediction of time to failure for entire event sequences. Using only instantaneous particle velocity statistics and without using information about the history of previous events, coefficients of determination in the range R2 = 0.81–0.96 were obtained.

Applied Mechanics doi: 10.3390/applmech7010014

Authors: Homa Haghighi Girum Urgessa

Traditional expansion joints in bridge structures are prone to durability problems, such as leakage, corrosion, and high maintenance demands, which can significantly reduce service life. To overcome these limitations, ultra-high-performance concrete (UHPC) link slabs have emerged as an effective jointless solution; however, their mechanical performance and sensitivity to key design and modeling parameters are not yet fully understood. This study presents a nonlinear finite element investigation of UHPC link slabs using the Concrete Damaged Plasticity (CDP) model in ABAQUS. A baseline model, validated against the experimental results, was established with a link slab length of 1100 mm and representative material and detailing properties. A systematic sensitivity analysis was then performed by varying five geometrical parameters (link slab length and thickness, debonding length, reinforcement diameter, and reinforcement spacing) and five numerical/material parameters (non-debonding and debonding interface friction coefficient, UHPC and normal concrete compressive strength, and steel yield strength). For each case, the load–displacement response was examined through initial stiffness (K0), yield and peak load–deformation values (Py, Δy and Pu, Δu), and ductility ratio (μ). The results highlight the dominant role of reinforcement detailing; larger bar diameters and closer spacing substantially increased stiffness and strength while maintaining ductility. Debonding length emerged as a critical tuning parameter, with longer debonding improving ductility but slightly reducing strength. Slab thickness primarily influenced stiffness, whereas overall length showed minor effects on peak capacity. On the numerical side, steel yield strength proved to be the most influential input, affecting all response measures, while the non-debonding interface friction coefficient strongly governed yield capacity. Variations in the debonding friction coefficient, UHPC compressive strength, and normal concrete strength exhibited secondary influence within the tested ranges. Overall, the findings provide practical guidance for both the designing and detailing of UHPC link slabs and the calibration of FEM (finite element modeling) models. By clarifying which parameters most strongly govern stiffness, strength, and ductility, this study supports more reliable structural design and efficient numerical modeling of UHPC link slabs in accelerated bridge construction applications.

Applied Mechanics doi: 10.3390/applmech7010013

Authors: Spyridoula G. Farmaki Dimitrios A. Exarchos Vasileios Dracopoulos Anastasios Gkotzamanis Konstantinos G. Dassios Theodore E. Matikas

Recent advances in nanotechnology have highlighted the transformative potential of carbon-based nanomaterials, such as carbon nanofibers, carbon nanotubes, and graphene, in cementitious systems. These materials have shown a remarkable ability to enhance the mechanical strength, fracture toughness, and overall functional performance of cementitious composites. Their nanoscale dimensions and exceptional intrinsic properties allow for effective stress bridging, crack arrest, and matrix densification. Despite these promising features, the current understanding remains limited, particularly regarding their application to concrete. Furthermore, literature lacks systematic, parallel evaluations of their respective effectiveness in improving both mechanical performance and long-term durability, as well as their potential to impart true multifunctionality to concrete structures. It is worth noting that significant and statistically significant improvements in fracture behavior were observed at specific nanofiller concentrations, suggesting strong potential for the material system in next-generation innovative infrastructure applications. Experimental results demonstrated that both CNTs and GNPs significantly enhanced the mechanical performance of concrete, with flexural strength increases of approximately 49% and 38%, and compressive strength improvements of 22% and 47%, respectively, at optimum contents of 0.6 wt.% CNTs and 0.8 wt.% GNPs. SEM analyses confirmed improved matrix densification and interfacial bonding at these concentrations, while higher dosages led to agglomeration and reduced performance. This gap highlights the need for targeted experimental studies to elucidate the structure-property relationships governing these advanced materials.

Applied Mechanics doi: 10.3390/applmech7010012

Authors: Habib Shorekandi Nima Refahati Meysam Nouri Niyaraki

In this study, the influence of nanochitosan and kenaf fibers on the tensile strength, elastic modulus, and impact strength of polylactic acid (PLA)/natural rubber (Standard Malaysian Rubber, grade 20—SMR20) biocomposites was investigated experimentally using Response Surface Methodology (RSM). The independent variables included the weight percentage of nanochitosan (2, 4, and 6 wt%), kenaf fibers (5, 10, and 15 wt%), and SMR20 natural rubber (10, 20, and 30 wt%). Composite samples were prepared by melt mixing in an internal mixer and subsequently fabricated into test samples using hot compression molding in accordance with relevant standards. Tensile tests were conducted to evaluate tensile strength and elastic modulus, while Charpy impact tests were performed to assess impact strength. The results revealed that increasing nanochitosan content up to 4 wt% enhanced tensile strength, elastic modulus, and impact strength by 39%, 22%, and 27%, respectively; however, further addition (6 wt%) led to a decline in these properties due to nanoparticle agglomeration. Increasing kenaf fiber content to 15 wt% improved tensile strength, elastic modulus, and impact strength by 44%, 26%, and 37%, respectively, demonstrating their effective reinforcing role. The incorporation of SMR20 natural rubber significantly increased impact strength by 59% (at 30 wt%), while causing a reduction of 17% in tensile strength and 20% in elastic modulus, consistent with its elastomeric nature. Furthermore, field emission scanning electron microscopy (FESEM) was employed to examine the dispersion of nanochitosan and kenaf fibers within the PLA/SMR20 matrix, providing insights into the interfacial adhesion and failure mechanisms. The findings highlight the potential of optimizing natural filler and rubber content to tailor the mechanical performance of sustainable PLA-based biocomposites.

Applied Mechanics doi: 10.3390/applmech7010011

Authors: Carlos D. Constantino-Robles Francisco Alberto Castillo Leonardo Jessica Hernández Galván Yoisdel Castillo Alvarez Luis Angel Iturralde Carrera Juvenal Rodríguez-Reséndiz

This paper presents a systematic review conducted under the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) framework, analyzing 286 scientific articles focused on vibration-based predictive maintenance strategies for wind turbines within the context of advanced Prognostics and Health Management (PHM). The review combines international standards (ISO 10816, ISO 13373, and IEC 61400) with recent developments in sensing technologies, including piezoelectric accelerometers, microelectromechanical systems (MEMS), and fiber Bragg grating (FBG) sensors. Classical signal processing techniques, such as the Fast Fourier Transform (FFT) and wavelet-based methods, are identified as key preprocessing tools for feature extraction prior to the application of machine-learning-based diagnostic algorithms. Special emphasis is placed on machine learning and deep learning techniques, including Support Vector Machines (SVM), Random Forest (RF), Convolutional Neural Networks (CNN), Long Short-Term Memory networks (LSTM), and autoencoders, as well as on hybrid digital twin architectures that enable accurate Remaining Useful Life (RUL) estimation and support autonomous decision-making processes. The bibliometric and case study analysis covering the period 2020–2025 reveals a strong shift toward multisource data fusion—integrating vibration, acoustic, temperature, and Supervisory Control and Data Acquisition (SCADA) data—and the adoption of cloud-based platforms for real-time monitoring, particularly in offshore wind farms where physical accessibility is constrained. The results indicate that vibration-based predictive maintenance strategies can reduce operation and maintenance costs by more than 20%, extend component service life by up to threefold, and achieve turbine availability levels between 95% and 98%. These outcomes confirm that vibration-driven PHM frameworks represent a fundamental pillar for the development of smart, sustainable, and resilient next-generation wind energy systems.

Applied Mechanics doi: 10.3390/applmech7010010

Authors: Adil Yucel Alaeddin Arpaci Asli Bal Cemre Ciftci

This study investigates the dynamic behaviors of re-entrant unit-cell-shaped steel frames through numerical and experimental modal analyses. Inspired by re-entrant honeycomb structures, individual frame units were modeled to explore how natural frequencies vary with beam cross-sectional dimensions and frame angles. Twenty distinct frame models—incorporating four cross-sectional sizes (4 × 4 mm, 8 × 8 mm, 12 × 12 mm, and 16 × 16 mm) and five main frame angles (120°, 150°, 180°, 210°, and 240°)—were developed using 3D modeling and finite element analysis (FEA) tools, and the first eight natural frequencies and corresponding mode shapes were extracted for each model. The results reveal that lower modes exhibit global bending and torsional behaviors, whereas higher modes demonstrate increasingly localized deformations. It is found that the natural frequencies decrease in the straight frame configuration and increase in the hexagonal configurations, highlighting the critical influence of the frame geometry. Increasing the cross-sectional size consistently enhances the dynamic stiffness, particularly in hexagonal frames. A quadratic polynomial surface regression analysis was performed to model the relationship of the natural frequency with the cross-sectional dimension and frame angle, achieving high predictive accuracy (R2 > 0.98). The experimental validation results were in good agreement with the numerical results, with discrepancies generally remaining below 7%. The developed regression model provides an efficient design tool for predicting vibrational behaviors and optimizing frame configurations without extensive simulations; furthermore, experimental modal analyses validated the numerical results, confirming the effectiveness of the model. Overall, this study provides a comprehensive understanding of the dynamic characteristics of re-entrant frame structures and proposes practical design strategies for improving vibrational performance, which is particularly relevant in applications such as machine foundations, vibration isolation systems, and aerospace structures.

Applied Mechanics doi: 10.3390/applmech7010009

Authors: Emmanouil Bacharidis Panagiotis Seventekidis Alexandros Arailopoulos

This work investigates a data-driven approach for detecting structural damage in the wing of a Cessna 172 aircraft using reduced-order finite element (FE) models. This study focuses on the ability of machine learning methods to generalize across different structural conditions, aiming to support reliable Structural Health Monitoring (SHM) in aeronautical applications. The wing was first modeled in detail using the FiniteElement Method, followed by the development of a simplified FE model to reduce computational cost while maintaining accuracy. The similarity between the two models was evaluated through modal analysis and the Modal Assurance Criterion (MAC). Dynamic excitation representing turbulence effects was applied to simulate healthy and damaged conditions, producing acceleration data used to train one-dimensional and two-dimensional neural network classifiers. The 1D models processed raw vibration signals, while the 2D models used image representations of the same data. Both architectures were tested against results from the detailed FE model to assess their generalization capability. The 2D networks achieved higher classification accuracy, demonstrating improved robustness in identifying both minor and severe damage. The findings highlight the potential of combining reduced FE models with data-driven methods for efficient and accurate aircraft wing damage detection.

Applied Mechanics doi: 10.3390/applmech7010008

Authors: Maria Luísa Braga Farinha Nuno Monteiro Azevedo Sérgio Oliveira

An explicit coupled two-dimensional (2D) hydromechanical model (HMM) that can simulate discontinuous features in the foundation, as well as the effects of grout curtains and drainage systems, is employed to evaluate the influence of key parameters such as dam height, foundation behaviour, joint patterns, joint stiffness and strength, hydraulic apertures, and grout curtain permeability. A parametric sensitive study using four gravity dams, and a real case study of an operating dam are presented. The results presented show that dam height influences the relationship between water level in the reservoir and drain discharges, with higher dams showing more pronounced curved nonlinearity. The strength properties of the concrete–rock interface are also shown to have a meaningful influence on the HM response, especially for an elastic foundation and for higher dams, showing the need to properly characterize this interface through in situ testing. The joint aperture at nominal zero stress is shown to be the parameter with the most significant effect on the HM response. The results also show that a progressive degradation scenario of the concrete–rock interface or of the grout curtain permeability is easier to identify through the hydraulic measurements than in the mechanical displacement field.

Applied Mechanics doi: 10.3390/applmech7010007

Authors: Xolani Prince Hadebe Bernard Xavier Tchomeni Kouejou Alfayo Anyika Alugongo Desejo Filipeson Sozinando

Large-diameter butterfly valves are essential control components in high-flow hydraulic systems, where blade geometry directly impacts operational reliability, energy efficiency, and lifecycle cost. This study presents an integrated structural–hydraulic optimization of a DN3000 Boving butterfly valve blade rated for a maximum operating pressure of 10 bar with comparative analysis of a conventional flat blade and an optimized curved blade. The work applies a CFD–FEM framework specifically to DN3000 Southern African valves, which is rare in the literature. Numerical simulations evaluated stress distribution, deformation, pressure losses, and flow stability under design and hydrostatic test conditions. The curved blade achieved a 58.6% reduction in peak von Mises stress, a 50% reduction in weight, a 22% reduction in load loss, and a 33% reduction in actuation torque requirements, while maintaining seal integrity. Cost analysis revealed a 50% reduction in material costs and simplification of manufacturing. The results confirm that the introduction of curvature significantly improves structural strength and hydraulic efficiency, thus providing a reproducible framework for the design of lighter and more economical valves in hydropower, municipal and industrial applications.

Applied Mechanics doi: 10.3390/applmech7010006

Authors: Tong Wang Xin Du Shufa Chen Qixin Sun Yue Jiang Hengjie Dong

This study conducts systematic experimental and numerical investigations to address the parameter calibration issue in the discrete element model of seashells, aiming to establish a high-fidelity numerical model that accurately characterizes their macroscopic mechanical behavior, thereby providing a basis for optimizing parameters of seashell crushing equipment. Firstly, intrinsic parameters of seashells were determined through physical experiments: density of 2.2 kg/m3, Poisson’s ratio of 0.26, shear modulus of 1.57 × 108 Pa, and elastic modulus of 6.5 × 1010 Pa. Subsequently, contact parameters between seashells and between seashells and 304 stainless steel, including static friction coefficient, rolling friction coefficient, and coefficient of restitution, were obtained via the inclined plane method and impact tests. The reliability of these contact parameters was validated by the angle of repose test, with a relative error of 5.1% between simulation and measured results. Based on this, using ultimate load as the response indicator, the PlackettBurman experimental design was employed to identify normal stiffness per unit area and tangential stiffness per unit area as the primary influencing parameters. The Bonding model parameters were then precisely calibrated through the steepest ascent test and design, resulting in an optimal parameter set. The error between simulation results and physical experiments was only 3.8%, demonstrating the high reliability and accuracy of the established model and parameter calibration methodology.

Applied Mechanics doi: 10.3390/applmech7010005

Authors: Liguang Kang Sandeep Suresh Babu Muhammet Muaz Yalçın Abdel-Hamid Ismail Mourad Mostafa S. A. ElSayed

This paper presents a unified aerodynamic design and optimization framework for morphing Blended-Wing-Body (BWB) Unmanned Aerial Vehicles (UAVs) operating in subsonic and near-transonic regimes. The proposed framework integrates parametric CAD modeling, Computational Fluid Dynamics (CFD), and surrogate-based optimization using Response Surface Methodology (RSM) to establish a generalized approach for geometry-driven aerodynamic design under multi-Mach conditions. The study integrates classical aerodynamic principles with modern surrogate-based optimization to show that adaptive morphing geometries can maintain efficiency across varied flight conditions, establishing a scalable and physically grounded framework that advances real-time, high-performance aerodynamic adaptation for next-generation BWB UAVs. The methodology formulates the optimization problem as drag minimization under constant lift and wetted-area constraints, enabling systematic sensitivity analysis of key geometric parameters, including sweep, taper, and twist across varying flow regimes. Theoretical trends are established, showing that geometric twist and taper dominate lift variations at low Mach numbers, whereas sweep angle becomes increasingly significant as compressibility effects intensify. To validate the framework, a representative BWB UAV was optimized at Mach 0.2, 0.4, and 0.8 using a parametric ANSYS Workbench environment. Results demonstrated up to a 56% improvement in lift-to-drag ratio relative to an equivalent conventional UAV and confirmed the theoretical predictions regarding the Mach-dependent aerodynamic sensitivities. The framework provides a reusable foundation for conceptual design and optimization of morphing aircraft, offering practical guidelines for multi-regime performance enhancement and early-stage design integration.

Applied Mechanics doi: 10.3390/applmech7010004

Authors: Mohamed-Fouad Maouche Mabrouk Hecini

This work presents an analytical homogenization model developed to predict the tensile and bending behavior of double-wall corrugated cardboard. The proposed approach replaces the complex three-dimensional geometry, composed of five paper layers, with an equivalent two-dimensional homogenized plate. Based on lamination theory and enhanced by sandwich structure theory, the model accurately captures the orthotropic behavior of the material. To achieve this objective, three configurations of double-wall corrugated cardboard were investigated: KRAFT LINER (KL), DUOSAICA (DS), and AUSTRO LINER (AL). A comprehensive experimental characterization campaign was conducted, including physical analyses (density measurement, SEM imaging, and XRD analysis) and mechanical testing (tensile tests), to determine the input parameters required for the homogenization process. The proposed model significantly reduces geometric complexity and computational cost while maintaining excellent predictive accuracy. Validation was performed by comparing the results of a 3D finite element model (ANSYS-19.2) with those obtained from the homogenized H-2D model. The differences between both approaches remained systematically below 2%, confirming the ability of the H-2D model to accurately reproduce the axial and flexural stiffnesses of double-wall corrugated cardboard. The methodology provides a reliable and efficient framework specifically dedicated to the mechanical analysis and optimization of corrugated cardboard structures used in packaging applications.

Applied Mechanics doi: 10.3390/applmech7010003

Authors: Ali Makke Julien Gardan Naman Recho Marouene Zouaoui

This methodology investigates the determination of the fracture toughness of 3D-printed specimens under monotonic loading conditions. The application is based on the use of a Single Edge Notch Bending (SENB) specimen made by a 3D-printing process (17-4PH stainless steel). The load–displacement curves exhibited linear behavior until crack initiation, indicating that the Linear Elastic Fracture Mechanics (LEFM) can be used under a small-scale yielding assumption. This study extends a previous methodology, originally applied to a polymer, to a metal additively manufactured material. The methodology established in the paper represents a major outcome: the ability to characterize the fracture toughness of the material. This study extends our previous Digital Image Correlation-based methodology from thermoplastic polymers to 17-4PH stainless steel produced by metal additive manufacturing (ADAM). Its novelty lies in combining DIC with a finite element sub-model to evaluate fracture parameters, enabling accurate crack initiation detection in challenging metal AM specimens, and providing a methodology that can be generalized to other metals and AM processes. The aim of this study is to establish a robust DIC-based methodology for the identification of crack initiation and the determination of fracture toughness parameters (K_IC and J) in 3D-printed 17-4PH stainless steel produced by the ADAM process.

Applied Mechanics doi: 10.3390/applmech7010002

Authors: Anastasia Bogdanova Anna Kamenskikh Andrey Muhametshin Yuriy Nosov

The present article relates to the description of phenomenological relations of amorphous material behavior within the framework of viscoelasticity and elastic-viscoplasticity theory, as well as to the creation of its digital analog. Ultra-high-molecular-weight polyethylene (UHMWPE) is considered in the study. The model is based on the results of a series of experimental studies. Free compression of cylindrical specimens in a wide range of temperatures [−40; +80] °C and strain rates [0.1; 4] mm/min was performed. Cylindrical specimens were also used to determine the thermal expansion coefficient of the material. Dynamic mechanical analysis (DMA) was performed on rectangular specimens using a three-point bending configuration. Maxwell and Anand models were used to describe the material behavior. In the framework of the study, the temperature dependence of a number of parameters was established. This influenced the mathematical formulation of the Anand model, which was adapted by introducing the temperature dependence of the activation energy, the initial deformation resistance, and the strain rate sensitivity coefficient. Testing of the material models was carried out in the process of analyzing the deformation of a spherical bridge bearing with a multi-cycle periodic load. The load corresponded to the movement of a train on a bridge structure, without taking into account vibrations. It is shown that the viscoelastic model does not describe the behavior of the material accurately enough for a quantitative analysis of the stress–strain state of the structure. It is necessary to move on to more complex models of material behavior to minimize the discrepancy between the digital analog and the real structure; it has been established that taking into account plastic deformation while describing UHMWPE would allow this to be performed.

Applied Mechanics doi: 10.3390/applmech7010001

Authors: Harouna Illou Abdoulaye Rabii El Maani

This paper presents a numerical study of fluid–structure interaction (FSI) applied to wind turbines, combining computational fluid dynamics (CFD) and finite element analysis (FEA). The study focuses on a 3D wind turbine blade inspired by the GE 1.5XLE model. The blade features a twisted geometry with S818, S825, and S826 aerodynamic profiles, and is made of an orthotropic composite material with variable thickness and an internal spar. The fluid domain is defined by two circular sections upstream and downstream, aligned along the Z-axis. Simulations are performed under a wind speed of 12 m/s and a rotational speed of −2.22 rad/s (Tip Speed Ratio (TSR) = 8), with air modeled as an incompressible fluid at ambient temperature. On the CFD side, a periodic and symmetric modeling approach is applied, reducing the fluid domain to one-third of the full configuration by simulating flow around a single blade and extrapolating results to the remaining ones. This method achieves a 47% reduction in computation time while maintaining high accuracy in aerodynamic results. On the FEA side, spar condensation is performed by creating a superelement using the substructuring method. This strategy reduces structural computation time by 45% while preserving reliable predictions of displacements, stresses, and natural frequencies. These results confirm the effectiveness of the proposed techniques for accurate and computationally efficient aeroelastic simulations.

Applied Mechanics doi: 10.3390/applmech6040091

Authors: Rafael Shaikhutdinov

Creep in metals as a phenomenon has been comprehensively studied in solid mechanics as well as in materials science. This interest stems from two key motivations: assessing the strength characteristics of components subjected to prolonged exposure at high temperatures and enhancing our understanding of plastic deformation mechanisms. As it is known, the mechanics of deformable solids employ constitutive equations when describing creep behavior, whereas strength physics utilize models aimed at quantifying a particular creep deformation mechanism or mechanisms in novel materials and to predict the performance of the parts manufactured from them. However, such models are rarely encountered within traditional mechanics problem-solving frameworks. To bridge this gap, this study demonstrates how some classic boundary value problems can incorporate the kinetic equation of a metal creep model with a real structural parameter derived from the theory of irreversible deformations. The main derivation steps and numerical solutions are provided for steady and transient creep conditions, along with visualizations illustrating the distribution of actual structural parameters. This research outlines promising pathways for incorporating diverse structural creep models—typically associated with materials science—into solid mechanics. These findings lay the groundwork for more accurate predictions of evolving material properties in applications where creep deformations play a critical role.

Applied Mechanics doi: 10.3390/applmech6040090

Authors: Hana Driss Abderrahim El Mahi Mourad Bentahar Moez Beyaoui Mohamed Haddar

This paper presents the mechanical characterisation of sandwich composites. Different specimen configurations have been tested with a three-point bending load and their mechanical behavior has been discussed. In addition, the acoustic emission technique was used to detect the onset of damage mechanisms and to monitor their evolution. The proposed analysis is based on processing recorded acoustic emission bursts. An unsupervised classification approach, combining the k-means algorithm with Principal Component Analysis (PCA), is used to group the detected acoustic events. The cluster analysis of the acquired data allows for correlation with the damage mechanisms occurring in sandwich composites. In addition to the advantages of multivariate data analysis, the results highlight the influence of sensor placement on the analysis of damage mechanisms is investigated. A suitable sensor configuration is proposed to improve the detection of acoustic emission activity. The originality of this work lies in the combined mechanical–AE interpretation that provides new insight into the damage behaviour of both a synthetic and a bio-based sandwich material. The comparative analysis of these two types of materials, coupled with a dedicated evaluation of sensor placement effects on defect detection, offers a contribution not previously reported in the literature.

Applied Mechanics doi: 10.3390/applmech6040089

Authors: Bekzodjon Fayziev Otabek Sagdullaev Shukhrat Djalilov Odil Khaydarov Jabbor Mustofoqulov Erkin Akhmedov Asror Mustafakulov Akbar Toyirov

Degradable solute transport in porous media significantly influences various ecological, geological, and industrial processes. In this paper, a mathematical model for solute transport in porous media with varying hydrodynamic dispersion is examined, integrating balance and kinetic equations alongside initial and boundary conditions. The model is enhanced by include variable hydrodynamic dispersion. Numerical approaches are utilized to address the problem, and a solution algorithm founded on the finite difference method is introduced. Computer simulations are conducted to examine the impact of different model parameters on solute transport, and the findings are evaluated. Numerical tests were performed for constant dispersion and three representative spatially variable forms—exponential, linear, and parabolic—for same other model parameters. Simulations show that neglecting diffusion/dispersion significantly delays the transport of material and underestimates both aqueous concentrations and adsorbed reserves. The results demonstrate that accounting for variable hydrodynamic dispersion significantly enhances the accuracy of solute transport predictions. The exponential form of dispersion produces stronger spreading effects, while the linear and parabolic forms show moderate variations. These findings underline the importance of incorporating scale-dependent dispersion in modeling contaminant migration in porous media.

Applied Mechanics doi: 10.3390/applmech6040088

Authors: Hagen Bankwitz Jörg Matthes Jörg Hübler

Additive Manufacturing (AM) using Fused Layer Modelling (FLM) often results in polymer components with limited and highly anisotropic mechanical properties, exhibiting structural weaknesses in the layer direction (Z-direction) due to low interlaminar adhesion. The main objective of this work was to investigate and quantify these mechanical limitations and to develop strategies for their mitigation. Specifically, this study aimed to (1) characterize the anisotropic behavior of unreinforced Polycarbonate (PC) components, (2) evaluate the effect of continuous, unidirectional (UD) carbon fiber tape reinforcement on mechanical performance, and (3) validate experimental findings through Finite Element Method (FEM) simulations to support predictive modeling of reinforced FLM structures. Methods involved experimental tensile and 3-point bending tests on specimens printed in all three spatial directions (X, Y, Z), validated against FEM simulations in ANSYS Composite PrepPost (ACP) using an orthotropic material model and the Hashin failure criterion. Results showed unreinforced samples had a pronounced anisotropy, with tensile strength reduced by over 70% in the Z direction. UD tape integration nearly eliminated this orthotropic behavior and led to strength gains of over 400% in tensile and flexural strength in the Z-direction. The FEM simulations showed very good agreement regarding initial stiffness and failure load. Targeted UD tape reinforcement effectively compensates for the weaknesses of FLM structures, although the quality of the tape–matrix bond and process reproducibility remain decisive factors for the reliability of the composite system, underscoring the necessity for targeted process optimization.

Applied Mechanics doi: 10.3390/applmech6040087

Authors: Maria Anna De Rosa Maria Lippiello

This paper investigates the effects of shear deformation on the flutter and divergence instabilities of a cantilever beam subjected to a concentrated mass and applied dynamic couple. The beam is modeled using classical and truncated Timoshenko beam theory, accounting for both shear deformation and rotary inertia. The inclusion of rotary inertia is shown to significantly influence the dynamic response, particularly for beams with greater thickness. According to Hamilton’s principle, the equations of motion for the cantilevered beam are derived, applying both classical and truncated Timoshenko beam theories. Auxiliary functions are utilized to solve the resulting system analytically. Various numerical examples are presented, illustrating typical results to demonstrate the effectiveness of the proposed approach. The numerical findings show significant convergence and computational effectiveness. The effect of the location of a concentrated mass and the dynamic couple applied at the free end is analyzed for various beam slenderness ratios and curvature positions, emphasizing their impact on modifying the critical instability limits. To highlight the significance of shear effects, a comparison is made between the outcomes of the Timoshenko model and those of the Euler-Bernoulli beam model, showing notable variations in the anticipated divergence and flutter stability characteristics. All the examples were executed using both classical theory and the truncated Timoshenko theory, and the findings indicated a remarkable level of convergence. Finally, a numerical comparisons with literature papers was performed. The results achieved showed strong alignment.

Applied Mechanics doi: 10.3390/applmech6040086

Authors: Vladimir Kobelev

This manuscript examines the rotational dynamics of rigid bodies in five-dimensional Euclidean space. This results in ten coupled nonlinear differential equations for angular velocities. Restricting rotations along certain axes reduces the 5D equations to sets of 4D Euler equations, which collapse to the classical 3D Euler equations. This demonstrates consistency with established mechanics. For bodies with equal principal moments of inertia (e.g., hyperspheres and Platonic solids), the rotation velocities remain constant over time. In cases with six equal and four distinct inertia moments, the solutions exhibit harmonic oscillations with frequencies determined by the initial conditions. Rotations are stable when the body spins around an axis with the largest or smallest principal moment of inertia, thus extending classical stability criteria into higher dimensions. This study defines a 5D angular momentum operator and derives commutation relations, thereby generalizing the familiar 3D and 4D cases. Additionally, it discusses the role of Pauli matrices in 5D and the implications for spin as an intrinsic property. While mathematically consistent, the hypothesis of a fifth spatial dimension is ultimately rejected since it contradicts experimental evidence. This work is valuable mainly as a theoretical framework for understanding spin and symmetry. This paper extends Euler’s equations to five dimensions (5D), demonstrates their reduction to four dimensions (4D) and three dimensions (3D), provides closed-form and oscillatory solutions under specific inertia conditions, analyzes stability, and explores quantum mechanical implications. Ultimately, it concludes that 5D space is not physically viable.

Applied Mechanics doi: 10.3390/applmech6040085

Authors: Jianfeng Fang Gentian Hong Xin Wen Runmin Wang Qiang Shentu Tao Chen Weichao Li

A method based on a statically indeterminate planar frame model was developed for the analysis and evaluation of box-type subgrade structures in high-speed railways. The objective of this study is to establish a concise and mechanically rigorous framework capable of quantifying the effects of key geometric parameters on bending moments, shear forces, and slab deflection, thereby providing guidance for structural refinement. Symbolic derivation and structural mechanics theory are combined to formulate the analytical model, and finite element simulations in Abaqus are used to verify the theoretical predictions under the design loads of the Quzhou–Lishui railway section located between Quzhou City and Lishui City in Zhejiang Province, China. Key findings show the maximum bending moments at the slab center and web-slab junction, reaching 14,818 kN·m, and the maximum shear forces of 16,934 kN at the web-slab junction. The top slab center showed the maximum deflection, approximately 7.5 × 10−2 mm. Simulation errors were below 5%. The optimization results recommend a web spacing of 4.5–5 m and a web height of 5–8 m. In an engineering case, reducing the web spacing from 6 m to 5 m and adjusting the web height from 7 m to 6.5 m dropped the top-slab mid-span bending moment from 10,628 kN·m to 5603 kN·m (an 89.7% reduction). Concrete use fell by 2.61% (from 24,900 to 24,250 m3/km), and overall costs dropped by about 5%. These findings demonstrate that the proposed analytical method provides an effective basis for rational parameter selection and preliminary structural design of box-type railway subgrades.

Applied Mechanics doi: 10.3390/applmech6040084

Authors: Felix Deckert Lukas Lippold Thomas Most Carsten Könke

Within the present paper, Physics-Informed Neural Networks (PINN) are investigated for the analysis of frame structures in two dimensions. The individual structural elements are represented by Euler–Bernoulli beams with additional axial stiffness. The transverse and axial displacements are approximated by individual neural networks and the differential equations are considered by minimizing a joined global loss function within the simultaneous training process. The boundary conditions at the supports of the structure and the coupling conditions at the element connections are considered in the global loss function and specific weighting factors are defined and tuned within the training. The combination of several structural elements within one analysis by training a set of neural networks simultaneously by a joined loss function is the main novelty of the current study. The formulation of coupling conditions for different scenarios is illustrated. Additionally, a nondimensionalization approach is introduced in order to achieve an automatic scaling of the individual loss function terms. Several examples have been investigated as follows: a simple beam structure first with quadratic load and second with varying cross-section properties is analyzed with respect to the convergency of the networks accuracy compared to the analytical solutions. Two more sophisticated examples with several elements connected at rigid corners were investigated, where the fulfillment of the consistency of the displacements and the equilibrium conditions of the internal forces is a crucial condition within the loss function of the network training. The results of the PINN framework are verified successfully with traditional finite element solutions for the presented examples. Nevertheless, the weighting of the individual loss function terms is the crucial point in the presented approach, which will be discussed in the paper.

Applied Mechanics doi: 10.3390/applmech6040083

Authors: Anna Kim Adil Kadyrov Kirill Sinelnikov Karibek Sherov Vassiliy Yurchenko

Cutting fluids are widely used in mechanical engineering to reduce friction and heat generation during metal machining. However, during operation, these fluids become contaminated with metal particles, dust, and microorganisms, leading to degradation of their functional properties and environmental concerns. This study investigates the ultrasonic cleaning and regeneration of contaminated cutting fluids. A rheological model of the elastic–viscous medium was analyzed, and a physical model describing the ultrasonic cleaning mechanism was proposed. Experimental investigations were conducted to validate the theoretical assumptions. The results confirmed that ultrasonic treatment promotes dispersion and phase separation of the fluid, removes putrefactive odor, and partially destroys microorganisms. The regenerated fluid exhibited enhanced clarity and stability compared with the contaminated samples. The findings contribute to a deeper understanding of the physicochemical processes occurring during ultrasonic treatment and demonstrate the potential of this method for sustainable reuse of cutting fluids in industrial applications.

Applied Mechanics doi: 10.3390/applmech6040082

Authors: Mihaela Constantin Cătălina Dobre Anca Chelmuș Nicolae Băran Daniel Taban Beatrice Ibrean Daniel Dima Mugurel Oprea

Cyclone separators are widely used for gas–solid separation due to their robustness and low operating cost. This study focuses on the experimental validation of a single cyclone configuration and the development of a MATLAB-based numerical framework. The model employs a Euler–Lagrange approach to capture centrifugal, drag, and gravitational forces acting on spherical polyethylene particles (D = 5 mm). Laboratory-scale measurements of airflow, pressure drop, and separation efficiency showed strong agreement with the numerical model (deviation < 6%), confirming its reliability for the single cyclone case. Beyond this validated framework, exploratory simulations were carried out for series and parallel cyclone configurations to provide predictive insights into possible design trade-offs. Unlike high-fidelity CFD–DEM models, which are computationally intensive and allow detailed turbulence and particle–particle interactions, the present MATLAB model is simplified but transparent and fast to implement. Its originality lies in demonstrating a low-cost, experimentally calibrated tool that can support preliminary design decisions. The multi-cyclone results should be interpreted as predictive trends, as no direct experimental validation was possible within the present setup. These findings offer preliminary guidance for balancing efficiency, energy demand, and throughput in applied mechanics of multiphase flow systems.

Applied Mechanics doi: 10.3390/applmech6040081

Authors: Šárka Němcová Jan Heřmánek Pavel Crha Karolina Macúchová Václav Němec Radek Pobořil Tomáš Tichý Ondřej Uher Martin Smrž Tomáš Mocek

This article demonstrates that 3D-printed parts can replace metal parts in optomechanics in the correct circumstances. Three examples are shown: a clamping fork for pedestal holders where stability is important, an adjustable mirror holder where the rigidity is the main criterion, and a stray light shield where the transmissivity is critical. By combining carbon-fiber-reinforced polymers (CFRPs) with 3D printing, it is possible to produce components that fill the gap between standard 3D-printed plastics and metal parts in terms of strength and stability. These parts are designed to be lighter, more compact, and easier to modify, while keeping good mechanical properties such as resistance to vibration, shape accuracy, and controlled thermal expansion. The article focuses on the application of composite 3D printing on optomechanical components. It compares different methods of composite 3D printing, including fused filament fabrication (FFF) with either chopped fibers or with continuous fiber reinforcement. Three examples from the HiLASE Centre demonstrate how these parts are used in practice, confirming that it is indeed possible to 3D print components that are lighter and cheaper yet still highly functional compared to their off-the-shelf counterparts—for example, lightweight and stiff mounts, shielding against stray laser light, or flexible elements allowing fine mechanical adjustments. Simulations of the deformations are included to compare the printed and metal versions. The article ends with a summary of the benefits and limitations of using 3D-printed composites in optomechanics.

Applied Mechanics doi: 10.3390/applmech6040080

Authors: Jifan Zhang Hua Su Yiting Su Kun Zhou

This study proposes a combined finger seal configuration composed of different structural laminates. An equivalent dynamic model of the finger seal system, accounting for thermal effects, is established. The effects of configuration type and operating conditions, including pressure differential, rotor displacement excitation, and temperature, on the dynamic leakage and rubbing force of the combined finger seal are investigated. The finger seal composed of two structural forms (X-type and Y-type) of finger laminates in this paper has a comprehensive advantage in leakage rate and rubbing force compared with the finger seal composed of a single structural seal slice. Compared with the leakage performance of the combined type of finger seals with different finger beam lengths, the maximum leakage rate of the 3Y+2X type finger seal proposed in this paper can be reduced by 29%. For the 3Y+2X finger seal structure and the calculation conditions (including pressure difference, displacement excitation and temperature) of this work, as the pressure difference increases, the seal leakage rate increases, and the peak value and impulse of the rubbing force also increase. The increase in rotor displacement excitation leads to an increase in both the leakage rate and the rubbing force. The increase in environmental temperature leads to an increase in leakage rate of the finger seal, but both the peak value of the rubbing force and the impact force reduce. Under different pressure differences and displacement excitation, the sealing leakage in a 300 °C high-temperature environment is slightly greater than that at normal temperature, but the friction force is less than that at normal temperature.

Applied Mechanics doi: 10.3390/applmech6040079

Authors: Ralph Kenneth Castillo Neamul Khandoker Sumaiya Islam Abdul Md Mazid

Resistance spot welding is a process used to join overlapping metals using pressure and electric current, commonly applied in the automotive industry for joining car bodies. This study aimed to understand the mechanical performance of spot welds under dynamic impact conditions. Various welding schedules were tested to observe the effects of different welding currents and times on the impact energy absorbed by spot welds. The results showed that the impact energy absorbed ranged from 26 J to 98 J, with higher welding currents and times generally increasing the impact energy due to more heat input. However, excessive welding parameters led to decreased impact energy. Statistical analysis and modeling revealed that optimal impact energy is achieved with a welding current of 5 kA and welding time of 6.728 cycles.

Applied Mechanics doi: 10.3390/applmech6040078

Authors: Guilherme Garcia Madsen Mariana Alvarenga Alves Luiz Alberto Oliveira Rocha Elizaldo Domingues dos Santos William Ramires Almeida Liércio André Isoldi

Thin steel plates with stiffeners are widely employed in several branches of engineering, combining mechanical strength with low weight and serving as both structural and cladding components. However, the influence of the side-wall inclination angle of hat-stiffeners on the stiffness distribution and deflection patterns of steel plates remains insufficiently explored. This study conducts computational modeling to evaluate the deflection of thin steel plates reinforced with hat-stiffeners. The plates were considered simply supported and subjected to a uniformly distributed load. The Constructal Design method and the exhaustive search technique were employed, allowing for geometric evaluation and optimization. A fraction corresponding to 30% of the plate volume was removed and redistributed to generate longitudinal hat-stiffener geometries by varying its side-wall angle and thickness. The smaller base of the hat-stiffeners was imposed as a geometric constraint and therefore kept fixed. The results indicate a nonlinear trend between the side-wall angle, the moment of inertia, and the resulting deflection, leading to a new geometrical pattern that connects the angular inclination to the overall stiffness behavior of the plate. Angles between 105° and 130° provided the best performance, reducing the maximum deflection by 93.72% compared with the reference plate and improving it by around 7.5% relative to previous studies. These findings illustrate how geometric configuration can enhance performance in line with Constructal Design principles.

Applied Mechanics doi: 10.3390/applmech6040077

Authors: Riyam Basim Al-Tameemi Hashem Mazaheri Jumaa Salman Chiad Mahdi Shaban

Bone-anchored implants have transformed prosthetic technology by providing a promising alternative to traditional socket-based prostheses through enhanced stability, comfort, and natural limb functionality. These advancements result from developments in osseointegration techniques, improved surgical methods, and innovative implant materials. To address current limitations, continued research remains essential to enhance safety and effectiveness, thereby promoting wider adoption of these advanced prosthetic solutions. This study focuses on modeling bone-anchored implants for limb prostheses in amputees. The research evaluates structural behavior and performance of osseointegrated implants under various conditions while optimizing implant design. The investigation examines different materials including aluminum, Ti-6Al-4V, and Ti-6Al-4V coated with 10 µm platinum. Additionally, implants of different lengths (207 mm, 217 mm, and 197 mm) were analyzed. The results indicate that Ti-6Al-4V and Ti-6Al-4V coated with ten µm platinum reduce stress by 46% and 65%, respectively. Ti-6Al-4V coated with platinum demonstrates the lowest equivalent stress, highlighting the coating’s effectiveness. Furthermore, the coated implant exhibits the lowest deformation—22.92% less than aluminum and 5.13% less than uncoated Ti-6Al-4V. Shorter implant lengths reduce deformation through increased stiffness, whereas longer implants, such as the 217 mm length display greater deformation due to enhanced flexibility.

Applied Mechanics doi: 10.3390/applmech6040076

Authors: Spyridoula G. Farmaki Dimitrios A. Exarchos Panagiota T. Dalla Elias A. Ananiadis Vasileios Kechagias Alexandros E. Karantzalis Theodore E. Matikas

The increasing reliance on conventional coatings such as WC-Co raises serious environmental and health concerns due to the toxicity of cobalt and the ecological footprint of these materials. To address this challenge, the present study explores the development of eco-friendly multifunctional coatings via the Plasma Spray (PS) process, using titanium (Ti), silicon carbide (SiC), and tungsten carbide-cobalt (WC-Co) mixtures as alternative feedstocks. Steel substrates were coated under different deposition strategies (powder mixing, layer-by-layer) and current settings (800-900 A). The coatings were characterized by scanning electron microscopy (SEM/EDX), 3D profilometry, sliding wear testing, and potentiodynamic corrosion measurements. Results showed that Ti-WC (mix, 900 A) and Ti-SiC (layer, 900 A) coatings achieved the most favorable performance, combining excellent adhesion, uniform coverage, reduced porosity, and improved resistance to wear and corrosion compared to conventional Cr2O3 coatings. Notably, Ti-WC coatings provided surface roughness values comparable to Cr2O3, while significantly lowering the environmental impact. These findings demonstrate that PS-based Ti-WC and Ti-SiC systems can serve as sustainable and high-performance alternatives for protective applications in harsh environments, particularly in marine industries, supporting the transition toward coatings with reduced ecological footprint.

Applied Mechanics doi: 10.3390/applmech6040075

Authors: Eric Puntel

We consider an axysimmetric cylindrical vessel grown by surface deposition at the inner boundary. The residual stress in the vessel can vary, e.g., depending on the loading history during growth. Can we represent and characterize a stress-free material (namely, reference) configuration for the vessel? Extending an idea initially proposed for surface growth occurring on a fixed boundary, the material configuration is introduced as a two-dimensional manifold immersed in a three-dimensional space. The problem is first formulated in fairly general terms for an incompressible neo-Hookean material in plane strain and then specialized to material configurations represented by ruled surfaces. An illustrative example using geometric and material parameters of carotid arteries shows the characterization of different material configurations based on their three-dimensional slope and computes the corresponding residual stress fields. Finally, such a slope is shown to be in a one to one relationship with the customary measure of residual stress in arteries, i.e., the opening angle in response to a cut. The present work introduces a novel framework for residual stress and shows its applicability in a special setting. Several generalizations and extensions are certainly necessary in the following sections to further test and assess the proposed method.

Applied Mechanics doi: 10.3390/applmech6040074

Authors: Csaba Hajdu Norbert Hegyi

This paper introduces a hypergraph-based formalism for modeling kinematic and dynamic structures in robotics, addressing limitations of the existing formats such as Unified Robot Description Format (URDF), MuJoCo-XML, and Simulation Description Format (SDF). Our method represents mechanical constraints and connections as hyperedges, enabling the native description of multi-joint closures, tendon-driven actuation, and multi-physics coupling. We present a tensor-based representation derived via star-expansion, implemented in the Hypergraph Model Cognition Framework (HyMeKo) language. Comparative experiments show a substantial reduction in model verbosity compared to URDF while retaining expressiveness for large-language model integration. The approach is demonstrated on simple robotic arms and a quarter vehicle model, with derived state-space equations. This work suggests that hypergraph-based models can provide a modular, compact, and semantically rich alternative for the next-generation simulation and design workflows. The introduced formalism reaches 50% reduction compared to URDF descriptions and 20% reduction compared to MuJoCo-XML descriptions.

Applied Mechanics doi: 10.3390/applmech6040073

Authors: Rudicler Pereira Ramos Felipe Vahl Ribeiro Cristian da Conceição Gomes Thamires Alves da Silveira Arthur Behenck Aramburu Neftali Lenin Villarreal Carreno Angela Azevedo de Azevedo Rafael de Avila Delucis

The combined effects of accelerated carbonation and lime sludge incorporation on the mechanical and durability performance of fiber-cement composites were assessed in this study. Lime sludge was used to replace 0%, 10%, and 20% of the cement in the composites, which were then autoclave-cured and carbonated more quickly for two or eight hours. With LS20-C8 (20% lime sludge, 8 h carbonation) achieving the highest carbonation efficiency (74.0%), X-ray diffraction (XRD) verified the gradual conversion of portlandite into well-crystallized calcium carbonate (CaCO3). In terms of mechanical performance, LS20-C8 outperformed the control by increasing toughness by 16.7%, flexural strength by 14.2%, compressive strength by 14.6%, and compressive modulus by 20.3%. The properties of LS20-C8 were better preserved after aging under wetting-drying cycles, as evidenced by lower losses of toughness (10.0%) and compressive strength (10.1%) compared to the control (14.6% and 18.3%, respectively). The mechanical improvements were explained by optical microscopy, which showed decreased porosity and an enhanced fiber–matrix interface. Overall, the findings show that adding lime sludge to accelerated carbonation improves durability, toughness, strength, and stiffness while decreasing porosity. This method helps to value industrial byproducts and is a sustainable and efficient way to create long-lasting fiber-cement composites.

Applied Mechanics doi: 10.3390/applmech6030072

Authors: Szabolcs Fischer Dmytro Kurhan Mykola Kurhan Oleksii Tiutkin

In developing a mathematical model of a railway track, the question of determining the dimensions of the modeling domain inevitably arises. If the modeling area is too small, boundary effects may significantly influence the results, reducing their accuracy. Conversely, excessively large areas can increase computational complexity without substantial improvements in accuracy. An optimal choice of dimensions enables the balancing of computational costs and accuracy. Solving this problem is non-trivial, as it depends on numerous factors, primarily the type of mathematical model and the problem being addressed. In most cases, preference is given to minimal domain sizes that ensure the approach’s adequacy. The aim of this study is to justify the dimensions of the modeling domain by addressing such tasks as load scaling, introducing additional boundary conditions, and making relevant assumptions. The main object of the study is the minimum adequate longitudinal length of the track for the spatial model. The research is based on the analytical application of modern approaches in the theory of elasticity. The results are analyzed using mathematical methods, such as modeling the railway track through the propagation of elastic waves and finite element modeling. These findings can be applied to a wide range of problems related to the mathematical modeling of the stress–strain state of railway tracks.

Applied Mechanics doi: 10.3390/applmech6030071

Authors: Geraldo Cesar Rosario de Oliveira Vania Aparecida Rosario de Oliveira Carla Carvalho Pinto Luis Felipe Barbosa Marques Tuane Stefania Reis dos Santos Antonio dos Reis de Faria Neto Carlos Alexis Alvarado Silva Marcelo Sampaio Martins Fernando de Azevedo Silva Erick Siqueira Guidi

This study investigates the mechanical behavior of water-washable photosensitive resins used in masked stereolithography (mSLA) 3D printing, evaluating the effect of post-curing time (0, 5, 10, 30, and 60 min) and printing orientation (Flat [XY], Vertical [Z], and On-edge [XZ]) on the material characteristics. Specimens were manufactured according to ISO 527-2 type 1B and ISO 178 standards for tensile and bending tests, respectively. A Matlab algorithm was developed to automate the processing of experimental data. This tool enabled the extraction of parameters to fit distinct mathematical models for the elastic (linear) and nonlinear (polynomial) regimes, allowing the material response to be characterized at different curing times and print orientations. These models were implemented in Ansys Workbench for comparison with experimental results. The results show that increasing the post-curing time from 0 to 60 min raises the elastic modulus from 964.5 to 1892.4 MPa in the Flat [XY] orientation and from 774 to 1661.2 MPa in the Vertical [Z] orientation for tensile testing. In bending testing, the Flat [XY] orientation presented the best mechanical properties, while the Vertical [Z] and On-edge [XZ] orientations showed similar behavior. The numerical simulations adequately reproduced the experimental results, validating the developed constitutive models. Finally, a stress–strain correlation model is presented that enables estimation for any post-curing time between 0 and 60 min. This study provides essential data for optimizing 3D printing processes and developing structural applications with photopolymer resins.

Applied Mechanics doi: 10.3390/applmech6030070

Authors: Marta Mencarelli Luca Puggelli Bernardo Innocenti Yary Volpe

This study examines the influence of printing parameters and filament composition on the mechanical properties of 3D printed parts, building upon prior research in fused deposition modeling. Two combinations of printing parameters, 75% infill, 0° orientation, four outer shells, with either gyroid and 3D Honeycomb infill patterns—were analyzed across eleven materials, including acrylonitrile butadiene styrene, polylactic acid, polylactic acid-based composites, polyethylene terephthalate glycol, and high-impact polystyrene. Tensile, compression, and bending tests were performed on the printed specimens to determine stiffness and elastic modulus. Each material demonstrated different levels of variability and sensitivity to printing parameters under the various loading conditions, emphasizing that no single configuration is optimal across all scenarios. For example, the gyroid pattern led to increases up to ~35% in bending modules for common thermoplastic filaments and ~30% for stone-filled polymers, while in tensile stiffness, variations between infill patterns remained below 5% for other conventional polymers. These findings underline the load-specific nature of optimal parameter combinations and the influence of material-specific characteristics, such as filler content or microstructural homogeneity. This study provides quantitative insights that can support application-driven parameter selection in additive manufacturing, offering a comparative dataset across widely used and emerging filaments.

Applied Mechanics doi: 10.3390/applmech6030069

Authors: Ishara Madusankha Prageeth Nimantha Jayaweera Nipun Shantha Kahatapitiya Peshan Sampath Ashan Weeraratne Kasun Subasinghage Chamara Liyanage Akila Wijethunge Naresh Kumar Ravichandran Ruchire Eranga Wijesinghe

In human-centered robotic applications, safety, efficiency, and adaptability are critical for enabling effective interaction and performance. Incorporating electromagnetic continuously variable transmission (EM-CVT) systems into robotic designs enhances both safety and precise, adaptable motion control. The flexible power transmission offered by CVTs allows robots to operate across diverse environments, supporting various tasks, human interaction, and safe collaboration. This study presents a CVT-based mechanical subsystem developed using two cones and an intermediate belt-driven transmission mechanism, providing efficient power and motion transfer. The control subsystem consists of six strategically positioned electromagnets energized by signals from a microcontroller. This electromagnetic actuation enables rapid and precise adjustments to the transmission ratio, enhancing overall system performance. A linear relationship between slip percentage and gear ratio was observed, indicating that the control system achieves stable and efficient operation, with a measured power consumption of 2.95 W per electromagnet. Future work will focus on validating slip performance under dynamic loading conditions, integrating the system into robotic platforms, and optimizing materials and control strategies to enable broader real-world deployment.

Applied Mechanics doi: 10.3390/applmech6030068

Authors: Branka Bužančić Primorac Marko Vukasović Radoslav Pavazza Frane Vlak

A simple analytic procedure for the linear static analysis of short thin-walled beams with monosymmetric open cross-sections subjected to eccentric axial loading is presented. Under eccentric compressive loading, the beam is subjected to compression/extension, to torsion with influence of shear with respect to the principal pole and to bending with influence of shear in two principal planes. The approximate closed-form solutions for displacements consist of the general Vlasov’s solutions and additional displacements due to shear according to the theory of torsion with the influence of shear, as well as the theory of bending with the influence of shear. The internal forces and displacements for beams clamped at one end and simply supported on the other end, where eccentric loading is acting, are calculated using the method of initial parameters. The shear coefficients for the monosymmetric cross-sections introduced in these equations are provided. Solutions for normal stress and total displacements according to Vlasov’s general thin-walled beam theory, and those obtained with the proposed method taking shear influence into account, are compared with shell finite element solutions analyzing isotropic and orthotropic I-section beams. According to the results for normal stress relative differences, and Euclidean norm for displacements, it has been demonstrated that shear effects must be accounted for in the analysis of such structural problems.

Applied Mechanics doi: 10.3390/applmech6030067

Authors: Gabriele Liuzzo Miriam Parisi Pierluigi Fanelli

The accuracy of modal superposition methods for determining displacement or strain field of structures largely depends on the selection of modes relevant to its deformation. Analytical methods for modal selection have been developed to minimise errors in reconstructing deformation through a linear combination of modal shapes. This study constitutes an initial step towards the development of structural health-monitoring algorithms for large engineering machines, where continuous monitoring of strain and stress, assuming a linear elastic field, is critical. The focus is on selecting modes that significantly contribute to the reconstruction of static deformation of structures. A detailed analytical approach, derived from established structural dynamics principles, leads to the formulation of modal selection criteria. These criteria are based on two fundamental quantities from dynamic and elastic theory: the modal participation factor and internal strain potential energy. Three criteria are introduced: the directional participation factor criterion (DPFC), the global participation factor criterion (GPFC), and the internal strain potential energy criterion (ISPEC). While DPFC and GPFC rely on displacements, ISPEC uses strains. The methods are validated through a case study involving a rectangular plate subjected to various loads, demonstrating their applicability to complex deformation scenarios, which require the combination of multiple modes to fully describe the static deformation. The proposed criteria are formulated for linear elastic systems and are therefore applicable, in principle, to plate-like components, machine casings, thin structural panels, and certain civil and aerospace panels, under the assumptions of small strains, linear constitutive behaviour, and validity of modal superposition. The approach also represents a first step towards the integration of modal selection with machine learning for structural health-monitoring applications and presents a computational cost significantly lower than that of full finite element analyses.

Applied Mechanics doi: 10.3390/applmech6030066

Authors: Vladimir Saveljev Gwanghee Heo

Displacement measurement is a critical issue in mechanical engineering. The moiré effect increases the accuracy of contactless measurements. We theoretically estimated the sensitivity threshold of moiré measurements using a digital camera on various objects. The estimated sensitivity threshold can be as low as a sub-pixel. We confirmed this experimentally in laboratory tests with a static image on a screen and simulated movement with non-integer and fractional amplitudes. Additionally, we provide practical examples, such as displacement measurement tests conducted in laboratories and outdoors. We took simultaneous measurements in two directions. The results can be applied in public safety, particularly for monitoring the condition of engineering structures.

Applied Mechanics doi: 10.3390/applmech6030065

Authors: Minseop Sim Seonbong Lee

This study aimed to determine optimal forming conditions by comparing the compaction behavior and microstructural characteristics of two Fe-based Soft Magnetic Composite (SMC) powders, Somaloy 700HR 5P and Somaloy 130i 5P. A full factorial design was employed with powder type, compaction temperature, and punch speed as variables. Finite element modeling (FEM) using experimentally derived properties predicted density and stress distributions in toroidal geometries. 700HR 5P exhibited higher stress under most conditions, while both powders showed similar axial density gradients. Experimental results validated the simulations. SEM analysis revealed that 130i 5P had fewer microvoids and clearer particle boundaries. As revealed by TEM-EDS analyses, after heat treatment, both powders exhibited a tendency for the insulation layers to become more uniform and continuous. The insulation layer of 700HR 5P was relatively thicker but retained some pores, whereas that of 130i 5P was thinner yet exhibited smoother and more continuous coverage. XRD analysis indicated that both powders retained an α-Fe solid solution. These results demonstrate that powder properties, composition, and insulation stability significantly influence compaction and microstructural evolution. This work systematically compares the formability and insulation stability of two commercial Somaloy powders and elucidates process–structure–property relationships through an application-oriented evaluation integrating experimental design, FEM, and microstructural characterization, providing practical insights for optimal process design.

Applied Mechanics doi: 10.3390/applmech6030064

Authors: Hikmet Bal

Predicting oil film thickness at ball–raceway contacts under elastohydrodynamic lubrication (EHL) conditions remains a complex tribological challenge. This complexity arises from dynamic variations in contact load, rotational speed, hydrodynamic effects, and the nonlinear load–deformation characteristics of the contacting surfaces. This study presents a numerical investigation of oil film thickness variations corresponding lubricant properties in rolling bearings using a 5-degree-of-freedom (5-DoF) shaft–bearing model. The model incorporates isothermal EHL and a rigid shaft supported by a pair of angular contact ball bearings. The governing nonlinear equations of motion are solved iteratively via a quasi-static approach, coupling oil film thickness and contact force calculations. Results indicate that oil film thickness increases proportionally with both lubricant viscosity and shaft speed. A twofold increase in shaft speed results in approximately 57% enhancement in film thickness. Similarly, increasing viscosity elevates film thickness proportionally, while the pressure–viscosity coefficient significantly enhances film formation. Notably, the outer raceway exhibits a 13% thicker film than the inner raceway, owing to its higher surface conformity. Furthermore, low-speed operation under heavy loads induces mixed lubrication regimes, compromising film integrity. Results provides insight for lubricant selection and bearing design to mitigate starvation in industrial applications.

Applied Mechanics doi: 10.3390/applmech6030063

Authors: C. Bhargavi K S Sreekeshava B K Raghu Prasad

This scoping review paper provides an overview of the evolution, the current stage, and the future prospects of fracture studies on composite laminates. A fundamental understanding of composite materials is presented by highlighting the roles of the fiber and matrix, outlining the applications of various synthetic fibers used in current structural sectors. Challenges posed by interlaminar delamination, one of the critical failure modes, are highlighted. This paper systematically discusses the fracture behavior of these laminates under mixed-mode and complex loading conditions. Standardized fracture toughness testing methods, including Mode I Double Cantilever Beam (DCB), Mode II End-Notched Flexure (ENF) and Mixed-Mode Bending (MMB), are initially discussed, which is followed by a decade-wide chronological analysis of fracture mechanics approaches. Key advancements, including toughening mechanisms, Cohesive Zone Modeling (CZM), Virtual Crack Closure Technique (VCCT), Extended Finite Element Method (XFEM) and Digital Image Correlation (DIC), are analyzed. The review also addresses recent trends in fracture studies, such as bio-inspired architecture, self-healing systems, and artificial intelligence in fracture predictions. By mapping the trajectory of past innovations and identifying unresolved challenges, such as scale integration, dataset standardization for AI, and manufacturability of advanced architectures, this review proposes a strategic research roadmap. The major goal is to enable unified multi-scale modeling frameworks that merge physical insights with data learning, paving the way for next-generation composite laminates optimized for resilience, adaptability, and environmental responsibility.

Applied Mechanics doi: 10.3390/applmech6030062

Authors: Jude A. Osara

Thermodynamic free energy is used to elucidate the significance of energy dissipation-induced temperature rise on the performance, reliability, and durability of all systems, biological, chemical and physical. Transformation (a measure of reliability) and degradation (a measure of durability) are distinguished. The temperature rise mechanism is characterized by the microstructurothermal (MST) energy/entropy. A framework to quantify the contributions of the MST entropy to system transformation and degradation is introduced and demonstrated using diverse multi-physics systems: cardiovascular strain in humans, charge capacity of batteries, tribological wear of journal bearings, and shear strength of lubricating greases. Various levels of temperature-induced degradation are observed in the systems. Thermal degradation rate increases with process and energy dissipation rates. The benefits of active cooling on systems and materials are shown. This article is recommended to engineers, scientists, designers, medical doctors, and other system analysts for use in dissipation/degradation characterization and minimization.

Applied Mechanics doi: 10.3390/applmech6030061

Authors: Gul Jamil Shah Muhammad Rizwan ul Haq Jeng-Ywan Jeng

Additive Manufacturing (AM) has revolutionized the production of intricate geometries tailored to customized functional mechanical properties, making it widely adopted across various industries, including aerospace, automotive, and biomedical sectors. However, the fabrication of mechanical springs has remained largely constrained by conventional manufacturing techniques, which limit their cross-sectional geometries to regular shapes, thereby restricting their mechanical performance and energy absorption capabilities. This limitation poses a significant challenge in applications where enhanced load-bearing capacity, energy absorption, and tailored stiffness characteristics are required. To address this issue, this study investigates the influence of coil shape on the mechanical properties of wave springs, specifically focusing on load-bearing capacity, energy absorption, stiffness, and compression behavior during cyclic loading and unloading. Nine contact-type wave springs with distinct coil shapes—square, rectangular, pentagonal, hexagonal, heptagonal, octagonal, quadro, circular (4 waves per coil), and circular (6 waves per coil)—were designed and fabricated using MultiJet Fusion (MJF) technology. Uni-axial compression testing was conducted over ten loading–unloading cycles to evaluate their mechanical performance and deformation characteristics. The results indicate that wave springs with square and rectangular coil shapes exhibit the highest energy absorption while maintaining the lowest stiffness and minimal energy loss during the first ten loading–unloading cycles. Furthermore, experimental findings were validated using finite element analysis (FEA) under identical boundary conditions, demonstrating close agreement with a deviation of only 2.3% compared with the experimental results. These results highlight AM’s potential for customizing wave springs with optimized mechanical performance.

Applied Mechanics doi: 10.3390/applmech6030060

Authors: Eduard Klatt Bernd Zimmering Oliver Niggemann Natalie Rauter

This study presents an approach based on data-driven methods for determining the parameters needed to model time-dependent material behaviour. The time-dependent behaviour of the thermoplastic polymer polybutylene terephthalate is investigated. The material was examined under two conditions, one with and one without the inclusion of reinforcing short fibres. Two modelling approaches are proposed to represent the time-dependent response. The first approach is the generalised Maxwell model formulated through the classical exponential Prony series, and the second approach is a model based on fractional calculus. In order to quantify the comparative capabilities of both models, experimental data from tensile creep tests on fibre-reinforced polybutylene terephthalate and unreinforced polybutylene terephthalate specimens are analysed. A central contribution of this work is the implementation of a machine-learning-ready parameter identification framework that enables the automated extraction of model parameters directly from time-series data. This framework enables the robust fitting of the Prony-based model, which requires multiple characteristic times and stiffness parameters, as well as the fractional model, which achieves high accuracy with significantly fewer parameters. The fractional model benefits from a novel neural solver for fractional differential equations, which not only reduces computational complexity but also permits the interpretation of the fractional order and stiffness coefficient in terms of physical creep resistance. The methodological framework is validated through a comparative assessment of predictive performance, parameter cheapness, and interpretability of each model, thereby providing a comprehensive understanding of their applicability to long-term material behaviour modelling in polymer-based composite materials.

Applied Mechanics doi: 10.3390/applmech6030059

Authors: Jamshaid Ul Rahman Uzma Nadeem Gulfam Haider Yaqoob Al Rahbi

Most physical systems exhibit nonlinear behavior while in motion, making their resolution challenging due to nonlinearity, dynamic effects, and sensitivity to parameters such as frequency and amplitude. Traditional analytical and numerical approaches can address these challenges but offer high computational costs, particularly in solving the system of free vibrations produced by the tapered beam. Predicting the behavior of this model is complicated, due to its high sensitivity and nonlinearity. Previously, standard neural network models have been used to solve dynamical systems, but they lack efficiency in handling nonlinearity. In this paper, we propose a novel deep learning model that predicts the amplitude of vibrations of a tapered beam. The primary focus of this study is to address the nonlinearity of the model and accurately predict the amplitude of vibrations. To solve this issue, we introduce a deep neural network designed to manage both nonlinearity and dynamical effects, including amplitude. The approach is significant in terms of computational and time efficiency compared to traditional numerical methods. The proposed work provides comparative results generated by the deep neural network, the backward difference formula as an analytical technique, and the Adams–Bashforth–Moulton predictor–corrector method as a numerical approach. The results demonstrate that our model outperforms existing numerical and analytical techniques. With the help of mean square error, Thiel’s inequality coefficient, and mean absolute error, the accuracy of our model can be verified; the lower these values, the more accurate our model will be. In our proposed model, the values are 8.389× 10−9 for mean square error, 5.563×10−4 for Thiel’s inequality coefficient, and 0.347 for mean absolute error; all these values are close to zero, signifying the accuracy of our model. The conclusion confirms that our proposed approach, even with changeable hyperparameters, is more suitable and accurate than numerical and analytical methods.

Applied Mechanics doi: 10.3390/applmech6030058

Authors: Virgil Gabriel Teodor Nicușor Baroiu Georgiana Alexandra Moroșanu Răzvan Sebastian Crăciun Vasilica Viorica Toniţă

Conical screw compressors are equipment used to compress air or other gases, using a mechanism consisting of two conically shaped rotors (screws), which rotate one inside the other. This specific design offers advantages in terms of its efficiency, durability and compactness. These compressors are characterized by high efficiency, efficient compression, low air loss, durability, compact dimensions and silent operation. In conical screw compressors, the screw axes are arranged at an angle, due to the conical shape of the screws. This arrangement allows for the progressive compression of the gas as it advances along the screws. On the one hand, the arrangement of the axes and the conical shape of the screws contribute significantly to the high performance of this type of compressor, but on the other hand, this shape makes it difficult to profile these active elements. The screw profiles of conical screw compressors are mutually enveloping, and this aspect is essential for the correct operation of the compressor. In this paper, a new algorithm for profiling the compressor’s external rotor starting from a known internal rotor shape is proposed. The proposed algorithm was developed at “Dunarea de Jos” University of Galati and was based on the observation that the compression chambers in conical screw compressors are sealed according to a curve that follows the axial section of the two screws, in a plane determined by their axes. Practically, the two screws admit a common contour of the axial section in the plane determined by their axes. Taking this aspect into account, the transverse profile of the outer screw can be determined by identifying the positions where contact will take place with the points belonging to the transverse profile of the inner screw. In order to verify the viability of this method, the volume occupied by the inner screw during its relative movement with respect to the outer screw was determined. This volume was compared with the volume of the outer rotor cavity, with the result demonstrating the identity of the two volumes.

Applied Mechanics doi: 10.3390/applmech6030057

Authors: Olfa Loukil Lucas Adelaide Veronique Bouteiller Marc Quiertant

The aim of this paper is to present the results of an experimental and numerical investigation into the degradation of reinforced concrete (RC) specimens subjected to an accelerated corrosion process using impressed current in the presence of chloride ions. The corrosion of the rebars was carried out using three current densities (50, 100, and 200 µA/cm2) and various exposure times. The experimental results characterised the internal degradation of the RC specimens through measurement of the corrosion product thicknesses at the steel–concrete interface; the widths, lengths and orientations of internal concrete cracks; and the external concrete crack widths. In addition, numerical modelling of the corroded RC specimens was conducted to describe the crack patterns. The comparison between the experimental and numerical results demonstrated a high degree of correlation, providing insights into the degradation process of RC specimens due to corrosion.

Applied Mechanics doi: 10.3390/applmech6030056

Authors: Ronald Herrera Daniel Garcés Abdelmadjid Benrabah Ahmad Al-Malabeh Rafael Jordá-Bordehore Luis Jordá-Bordehore

Empirical and numerical methodologies for the geomechanical assessment of underground excavations have evolved in recent years to adapt to the geotechnical and structural conditions of natural caves, enabling stability evaluation and ensuring safe conditions for speleological exploration. This study analyzes the evolution of the state of the art of these techniques worldwide, assessing their reliability and application context, and identifying the most suitable methodologies for determining the stability of the Al-Badia lava tube. The research was conducted through bibliographic analysis and rock mass characterization using empirical geomechanical classifications. Subsequently, the numerical boundary element method (BEM) was applied to compare the obtained results and model the stress–strain behavior of the cavity. The results allowed the classification of the Al-Badia lava tube into stable, transition, and unstable zones, using empirical support charts and determining the safety factors of the surrounding rock mass. The study site highlights that empirical methods are rather conservative, and numerical results align better with observed conditions.

Applied Mechanics doi: 10.3390/applmech6030055

Authors: Desejo Filipeson Sozinando Patrick Nziu Bernard Xavier Tchomeni Alfayo Anyika Alugongo

The interaction between thermal fields and mechanical loads in thin-walled cylindrical shells introduces complex dynamic behaviors relevant to aerospace and mechanical engineering applications. This study investigates the axial stress wave propagation in a circular cylindrical shell subjected to combined thermal gradients and time-dependent harmonic compression. A semi-analytical model based on Donnell–Mushtari–Vlasov (DMV) shells theory is developed to derive the governing equations, incorporating elastic, inertial, and thermal expansion effects. Modal solutions are obtained to evaluate displacement and stress distributions across varying thermal and mechanical excitation conditions. Empirical Mode Decomposition (EMD) and Instantaneous Frequency (IF) analysis are employed to extract time–frequency characteristics of the dynamic response. Complementary Finite Element Analysis (FEA) is conducted to assess modal deformations, stress wave amplification, and the influence of thermal softening on resonance frequencies. Results reveal that increasing thermal gradients leads to significant reductions in natural frequencies and amplifies stress responses at critical excitation frequencies. The combination of analytical and numerical approaches captures the coupled thermomechanical effects on shell dynamics, providing an understanding of resonance amplification, modal energy distribution, and thermal-induced stiffness variation under axial harmonic excitation across thin-walled cylindrical structures.

Applied Mechanics doi: 10.3390/applmech6030054

Authors: Pramod Yadav Shubham Gupta Dishant Sharma Arnab Chanda

Basketball requires intense movements like jumping and sudden changes in direction, increasing the risk of slips and falls due to poor shoe–court traction. Therefore, a significant demand is for good traction performance in basketball shoes, particularly in the heel region on different court surfaces, to prevent slipping. This study examined the traction performance of fifteen common basketball shoe designs that were considered and developed using thermoplastic polyurethane to assess the available coefficient of friction (ACOF) on popular floorings (hardwood, synthetic, and polyurethane) under dry and wet conditions using a robotic slip tester. Results indicate that the hardwood flooring provided better traction, followed by the synthetic flooring, while the polyurethane flooring showed reduced friction. The study also examined the traction with apparent contact areas. Shoes with herringbone and circular tread patterns demonstrated the highest traction on all flooring in dry conditions. This research is anticipated to help basketball shoemakers choose safer shoes for player safety and performance, providing a foundation for future research on shoe flooring interaction in basketball.

Applied Mechanics doi: 10.3390/applmech6030053

Authors: Hamid Khalilpoor Daniel Larouche X. Grant Chen André Phillion Josée Colbert

The formation of hot tearing during direct chill casting of aluminum alloys, specifically AA6111, is a significant challenge in the production of ingots for industrial applications. This study investigates the role of hydrostatic pressure and tensile stress in the formation of hot tearing during direct chill casting of rectangular ingots. Combining experimental results and finite element modeling with ABAQUS/CAE 2022, the mechanical behavior of the semi-solid AA6111 alloy was analyzed under different cooling conditions. “Hot” (low water flow) and “Cold” (high water flow) conditions were the two types of cooling conditions that produced cracked and sound ingots, respectively. The outcomes indicate that high tensile stress and localized negative hydrostatic pressure in the hot condition are the main factors promoting the initiation and propagation of cracks in the mushy zone, whereas the improvement of the cooling conditions reduces these defects.

Applied Mechanics doi: 10.3390/applmech6030052

Authors: Ahmed Saber A. M. Amer A. I. Shehata H. A. El-Gamal A. Abd_Elsalam

Crash boxes play a crucial role in automotive safety by absorbing impact energy during collisions. The advancement of additive manufacturing (AM), particularly Fused Deposition Modeling (FDM), has enabled the fabrication of geometrically complex and lightweight crash boxes. This study presents a comparative evaluation of the crashworthiness performance of five FDM materials, namely, PLA+, PLA-ST, PLA-LW, PLA-CF, and PETG, across four structural configurations: Single-Cell Circle (SCC), Multi-Cell Circle (MCC), Single-Cell Square (SCS), and Multi-Cell Square (MCS). Quasi-static axial compression tests are conducted to assess the specific energy absorption (SEA) and crush force efficiency (CFE) of each material–geometry combination. Among the materials, PLA-CF demonstrates superior performance, with the MCC configuration achieving an SEA of 22.378 ± 0.570 J/g and a CFE of 0.732 ± 0.016. Multi-cell configurations consistently outperformed single-cell designs across all materials. To statistically quantify the influence of material and geometry on crash performance, a two-factor ANOVA was performed, highlighting geometry as the most significant factor across all evaluated metrics. Additionally, a comparative test with aluminum 6063-T5 demonstrates that PLA-CF offers comparable crashworthiness, with advantages in mass reduction, reduced PCF, and enhanced design flexibility inherent in AM. These findings provide valuable guidance for material selection and structural optimization in FDM-based crash boxes.

Applied Mechanics doi: 10.3390/applmech6030051

Authors: Zhaohui Hu Shuai Mo Yuxuan Wang

Unlike previous studies focusing on two-layer structures or single-parameter effects, this work systematically investigates the influence of sheet layer combination modes on the mechanical properties of three-layer AA6063-T6 self-piercing riveting (SPR) joints through a combination of experimental testing and numerical simulation. Shear and cross-tensile tests were conducted on three-layer AA6063-T6 SPR joints with three distinct sheet layer combinations: T1 (top/middle: 100 × 40 mm2, bottom: 40 × 40 mm2), T2 (top/bottom: 100 × 40 mm2, middle: 40 × 40 mm2), and T3 (middle/bottom: 100 × 40 mm2, top: 40 × 40 mm2). Experimental results reveal significant differences in joint strength and failure modes across the three combinations. T3 joints exhibited the highest shear strength (9.16 kN) but the lowest cross-tensile strength (3.56 kN), whereas T1 joints showed the highest cross-tensile strength (4.97 kN) but moderate shear strength (8.76 kN). A high-fidelity finite element model was developed to simulate the SPR joint under varying sheet layer combinations, incorporating precise geometric details (0.25 mm mesh at critical zones) and advanced contact algorithms (friction coefficient μ = 0.2). Numerical simulations revealed the stress distribution and failure mechanisms under shear and cross-tensile loading, aligning well with experimental observations. Analysis highlights that the mechanical performance of the joint is governed by two key factors: (1) the stress redistribution in sheet layers due to combination mode variations, and (2) the interlocking strength between the rivet and sheets. These findings provide practical guidelines for optimizing sheet layer combinations in lightweight automotive structures subjected to mixed loading conditions.

Applied Mechanics doi: 10.3390/applmech6030050

Authors: Déborah de Oliveira Raphael Lima de Paiva Mayara Fernanda Pereira Rosenda Valdés Arencibia Rogerio Valentim Gelamo Rosemar Batista da Silva

Properly refrigerating hard-to-cut alloys during grinding is key to achieve high quality, strict tolerances, and good surface finishing. Nonetheless, literature about the influence of cooling-lubrication conditions (CLCs) on dimensional accuracy of ground components is still scarce. Thus, this work aims to evaluate surface quality, grinding power, and dimensional accuracy of Inconel 718 workpieces after grinding with silicon carbide grinding wheel at different grinding conditions. Four different CLCs were tested: flood, minimum quantity of lubrication (MQL) without graphene, and with multilayer graphene (MG) at two distinct concentrations: 0.05 and 0.10 wt.%. Different radial depths of cut values were also tested. The results showed that the material’s removed height increased with radial depth of cut, leading to coarse tolerance (IT) grades. Machining with the MQL WG resulted in higher dimensional precision with an IT grade varying between IT6 and IT7, followed by MQL MG 0.10% (IT7), MQL MG 0.05% (IT7-IT8), and flood (IT8). The lower tolerances achieved with MG were attributed to the lowering in the friction coefficient of the workpiece material sliding through the abrasive grits with no material removal (micro-plowing mechanism), thereby reducing grinding power and the removed height in comparison to the other CLC tested.

Applied Mechanics doi: 10.3390/applmech6030049

Authors: Yichi Zhang Bingen Yang

The sandwich plates in consideration are structures composed of a number of Lévy plate components laminated with viscoelastic layers, and they are seen in broad engineering applications. In vibration analysis of a sandwich plate, conventional analytical methods are limited due to the complexity of the geometric and material properties of the structure, and consequently, numerical methods are commonly used. In this paper, an innovative analytical method is proposed for vibration analysis of sandwich Lévy plates having different configurations of viscoelastic layers and using various models of viscoelastic materials. The focus of the investigation is on the determination of closed-form frequency response at any given frequencies. In the development, an s-domain state-space formulation is established by the Distributed Transfer Function Method (DTFM). With this formulation, closed-form analytical solutions of the frequency response problem of sandwich plates are obtained, without the need for spatial discretization. As one unique feature, the DTFM-based approach has consistent formulas and unified solution procedures by which analytical solutions at both low and high frequencies are obtained. The accuracy, efficiency, and versatility of the proposed analytical method are demonstrated in three numerical examples, where the DTFM-based analysis is compared with the finite element method and certain existing analytical solutions.

Applied Mechanics doi: 10.3390/applmech6030048

Authors: Tieshu Fan Kamran Behdinan

This paper develops an analytical turbulence model for open-ended squeeze film damper (SFD) application. Prandtl’s mixing length theory is adopted to describe the momentum transfer within the damper for its thin-film turbulent flow. A novel turbulence coefficient function is developed to describe the effective fluid viscosity such that the classical Reynolds equation remains applicable. Model validation is presented by (i) comparing the damping coefficient obtained by several existing empirical formulas and (ii) correlating the rotor dynamic prediction with the experimental measurement of an integrated rotor-SFD test rig. This work provides a reduced form of turbulence coefficient for certain SFD implementations. It quantifies the turbulence effect under different operating conditions, which is valued as a practical tool to assess the significance of turbulence consequences in rotor dynamic applications.

Applied Mechanics doi: 10.3390/applmech6030047

Authors: Tarik Zarrouk Jamal-Eddine Salhi Mohammed Nouari Mohammed Barboucha

Machining Nomex honeycomb cores is essential for manufacturing components that meet the stringent requirements of industrial sectors, but the complexity of this type of structure material requires specialized techniques to minimize defects, ensure optimal surface quality and extend cutting tool life. For this reason, an innovative machining technology based on longitudinal–torsional ultrasonic vibration assistance has been integrated into a CZ10 combined cutting tool, with the aim of optimizing the efficiency of conventional machining processes. To this end, a three-dimensional numerical model based on the finite element method, developed using Abaqus/Explicit 2017 software, was used to simulate the complex interactions between the cutting tool and the thin walls of the structures to be machined. This study aimed to validate the numerical model through experimental tests, quantifying the surface condition, cutting force and tool wear, while evaluating the impact of key machining parameters, such as feed rate and wall thickness, on process performance. The obtained results reveal a substantial reduction in cutting forces, varying from 20 to 40%, as well as a notable improvement in surface finish and a significant extension of tool life. These conclusions open up new perspectives for the optimization of industrial processes, particularly in high-demand sectors such as aeronautics.

Applied Mechanics doi: 10.3390/applmech6030046

Authors: Mhd Ayham Darwich Hasan Mhd Nazha Hiba Mohsen Ghadir Ahmad Salamah

This study investigates the biotribological performance of alumina–UHMWPE and alumina–PEEK hip implant couples through finite element simulation (ANSYS v24) and statistical inference (STATA v17). During gait cycle loading simulations, significant disparity in wear behaviour was observed. Alumina–UHMWPE demonstrated superior mechanical resistance, with a wear volume of 0.18481 mm3 and a wear depth of 6.93 × 10−4 mm compared to alumina–PEEK, which registered higher wear (volume: 8.4006 mm3; depth: 3.15 × 10−2 mm). Wear distribution analysis indicated alumina–UHMWPE showed an even wear pattern in comparison to the poor, uneven alumina-PEEK high-wear patterns. Statistical comparison validated these findings, wherein alumina–UHMWPE achieved a 27.60 hip joint wear index (HCI) value, which is better than that of alumina–PEEK (35.85 HCI), particularly regarding key parameters like wear depth and volume. This computational–statistical model yields a baseline design for biomaterial choice, demonstrating the potential clinical superiority of alumina–UHMWPE in reducing implant failure risk. While this is a simulation study lacking experimental validation, the results pave the way for experimental and clinical studies for further verification and refinement. The approach enables hip arthroplasty design optimization with maximal efficiency and minimal resource-intensive testing.

Applied Mechanics doi: 10.3390/applmech6020045

Authors: Livia Costa Iuri Bessa Juceline Bastos Aline Vale Teresa Farias

Predicting pavement performance is essential for highway planning and construction, considering traffic, climate, material quality, and maintenance. This study’s main objective is to evaluate Baosteel’s Slag Short Flow (BSSF) steel slag as a sustainable aggregate in pavement engineering by means of durability. The research integrates pavement performance prediction using BSSF and assesses its impact on fatigue resistance and percentage of cracked area (%CA). Using the Brazilian mechanistic-empirical design method (MeDiNa), eight scenarios were analyzed with soil–slag mixtures (0%, 25%, 50%, and 75% slag) in base and subbase layers under two traffic levels over 10 years. An asphalt mixture with 15% steel slag aggregate (SSA) was used in the surface layer and compared to a reference mixture. Higher SSA percentages were applied to the base layer, while lower percentages were used in subbase layers, facilitating field implementation. The resilient modulus (MR) and permanent deformation (PD) were design inputs. The results show that 15% SSA does not affect rutting damage, with %CA values below Brazilian limits for traffic of 1 × 106. The simulations confirm BSSF as an effective and sustainable alternative for highway pavement construction, demonstrating its potential to improve durability and environmental impact while maintaining performance standards.

Applied Mechanics doi: 10.3390/applmech6020044

Authors: Amalia Moutsopoulou Georgios E. Stavroulakis Markos Petousis Nectarios Vidakis Anastasios Pouliezos

References [...]

Applied Mechanics doi: 10.3390/applmech6020043

Authors: Kohei Tateyama Kazuma Abe Hiroyuki Fujiki Hisashi Sasaki Hiroyuki Yamada

The 2014 Mt. Ontake eruption in Japan highlighted the need for improved volcanic shelters. To contribute to their reinforcement, this study focuses on the energy absorption characteristics of pumice, particularly artificial pumice made from waste glass. Compression tests were conducted under unconfined and oedometric conditions using a universal testing machine, drop-weight testing machine, and split Hopkinson bar across a wide strain rate range (10−3 to 102 s−1). The deformation behavior was categorized into two types: one with a distinct initial peak followed by stress drop and another with a continuous transition to plateau deformation. Regardless of deformation type, the absorbed energy showed a positive dependence on strain rate. The average absorbed energy increased from approximately 1.6 MJ/m3 at 10−3 s−1 to over 4.3 MJ/m3 at 102 s−1. A simple predictive model was proposed to evaluate the energy absorption capacity of pumice reinforcement. The model’s predictions were in good agreement with experimental results for pumice layers up to 150 mm thick. These findings provide fundamental insights into the high strain rate behavior of artificial pumice and its potential application as a passive energy-absorbing material for impact-resistant volcanic shelters.

Applied Mechanics doi: 10.3390/applmech6020042

Authors: Carlo Brutti Corrado Groth Marco Evangelos Biancolini

Threaded connections are fundamental in engineering structures, yet their elastic–plastic behavior under load remains challenging to model analytically. The yield limit can be reached under relatively small external loads, and elastic–plastic behavior has predominantly been studied using finite element models. While these models are highly valuable, they are often restricted to specific cases. This paper presents a novel extension of Maduschka’s classical method, offering a fast and efficient analytical approach to evaluate the behavior of screw–nut–washer assemblies. The method tracks plastic strain progression from initial yielding to full yield conditions and is validated against high-fidelity axisymmetric and 3D finite element analyses (FEAs) across a range of thread dimensions (M16–M36). Results demonstrate strong agreement with FEA benchmarks while achieving significant computational speedups, making the method suitable for iterative and large-scale analyses. In addition, the comparison with results available in the literature further supports the reliability of the proposed method. Its robustness to variations in geometry, friction, and thread count positions it as a foundation for reduced-order models, ready for integration into complex finite element frameworks commonly used in structural health monitoring and digital twin technologies.

Applied Mechanics doi: 10.3390/applmech6020041

Authors: Bernardo Lopes Poncetti Dianelys Vega Ruiz Leandro Silva de Assis Lucas Bellini Machado Tiago Borges da Silva Ayokunle Adewale Akinlalu Marcos Massao Futai

Guaranteeing tunnel integrity is an important issue for several countries worldwide. Due to the continuous increase in the number of tunnels, as well as the aging of old tunnels, several countries and companies have created manuals to standardize tunnel inspection and assessment. Most manuals still specify just visual procedures for tunnel inspection; however, because of underground conditions, the structural system of tunnels is often accessible only by one side, thus posing difficulties to the accurate evaluation of the structural conditions of the tunnel using only visual inspection. A possibility to improve the effectiveness of tunnel inspection is the use of non-destructive testing (NDT), which will assist in obtaining information about the inner condition behind the tunnel wall. The current advancements in the NDT methods allow them to be employed in all the different kinds of inspections (initial, routine, special inspection) suggested by the manuals. Therefore, in an attempt to help in the decision about the application of each method, this work provides an overview of some international practices for tunnel inspections and shows a review of different NDT methods (traditional and new methods) applied to tunnel inspections. Furthermore, this study describes their workability, advantages, and capability, and classifies the best fitting of each in the inspection procedures.

Applied Mechanics doi: 10.3390/applmech6020040

Authors: Farahnaz Fallahtafti Arash Mohammadzadeh Gonabadi Kaeli Samson Megan Woods Iraklis Pipinos Sara Myers

Blocked or narrowed arteries restrict blood flow to the lower limbs, commonly leading to peripheral artery disease (PAD). Patients with PAD have been shown to have increased gait variability, which may contribute to higher rates of falls and worsen functional outcomes. Surgical revascularization seeks to restore blood flow to the legs, but it is unknown if this restoration enhances limb function. This study investigated whether gait variability changes in patients with PAD after revascularization surgery. Thirty-three patients with PAD exhibiting claudication symptoms were recruited for the study. Kinematic data were recorded using a motion capture system while the patients walked on a treadmill following a progressive treadmill protocol, both before and after undergoing revascularization surgery. Angular sagittal movements’ linear and nonlinear variability in the lower limbs were measured and compared before and after surgery across the ankle, knee, and hip joints. Following revascularization surgery, knee joint sample entropy (SampEn) decreased, suggesting improved gait regularity. Furthermore, the hip range of motion (ROM) significantly decreased, whereas the knee ROM significantly increased. The ankle joint showed significantly greater changes in the Lyapunov Exponent (LyE) relative to the pre-exercise condition compared with the hip and knee joints. No significant differences existed in the linear variability (standard deviation) of the ROM between joints. In individuals with PAD, revascularization surgery considerably increased knee ROM and gait regularity, indicating improved limb function and motor control. However, the ankle ROM remained unchanged, indicating the need for targeted strengthening exercises post-surgery.

Applied Mechanics doi: 10.3390/applmech6020039

Authors: Manasa Mariam Mammen Zafer Kayatas Dieter Bestle

Validating the safety and reliability of automated driving systems is a critical challenge in the development of autonomous driving technology. Such systems must reliably replicate human driving behavior across scenarios of varying complexity and criticality. Ensuring this level of accuracy necessitates robust testing methodologies that can systematically assess performance under various driving conditions. Scenario-based testing addresses this challenge by recreating safety-critical situations at varying levels of abstraction, from simulations to real-world field tests. However, conventional parameterized models for scenario generation are often resource intensive, prone to bias from simplifications, and limited in capturing realistic vehicle trajectories. To overcome these limitations, the paper explores AI-based methods for scenario generation, with a focus on the cut-in maneuver. Four different approaches are trained and compared: Variational Autoencoder enhanced with a convolutional neural network (VAE), a basic Generative Adversarial Network (GAN), Wasserstein GAN (WGAN), and Time-Series GAN (TimeGAN). Their performance is assessed with respect to their ability to generate realistic and diverse trajectories for the cut-in scenario using qualitative analysis, quantitative metrics, and statistical analysis. Among the investigated approaches, VAE demonstrates superior performance, effectively generating realistic and diverse scenarios while maintaining computational efficiency.

Applied Mechanics doi: 10.3390/applmech6020038

Authors: Jian Liu David Cheng Wang Pan Khin Oo Ty-Liyiah McCrimmon Shuang Bai

Polymer heat exchangers (HXs) are lightweight and cost-effective due to the affordability of raw polymer materials. However, the inherently low thermal conductivity (TC) of polymers limits their application in HXs. To enhance thermal conductivity polymer composites, two types of diamond powders, with particle sizes of 0.25 µm and 16.7 µm, were used as fillers, while Acrylonitrile Butadiene Styrene (ABS) served as the matrix. Composite polymer samples were fabricated, and their density and thermal conductivity were tested and compared. The results indicate that fillers with larger particle sizes tend to exhibit higher thermal conductivity. A polymer HX based on a Triply Periodic Minimal Surface (TPMS) structure was designed. The factors influencing the efficiency of polymer HXs were analyzed and compared with those of metal HXs. In polymer HXs, the polymer wall is the primary source of heat resistance. Additionally, the mechanical strength of 3D-printed polymer parts was evaluated. Finally, an HX was successfully fabricated using a polymer composite containing 50 wt% diamond powder via 3D printing.

Applied Mechanics doi: 10.3390/applmech6020037

Authors: Manfred Euler

Synchronization is a universal phenomenon in driven or coupled self-sustaining oscillators with important applications in a wide range of fields, from physics and engineering to the life sciences. The Adler–Kuramoto equation represents a reduced dynamical model of the inherent phase modulation effects. As a complement to the standard numerical approaches, the analytical solution of the underlying nonlinear dynamics is considered, giving rise to the study of kinematically equivalent elliptical gears. They highlight the cross-disciplinary relevance of mechanical systems in providing a broader and more intuitive understanding of phase modulation effects. The resulting gear model can even be extended to domains beyond classical mechanics, including quasi-relativistic kinematics and analogues of quantum phenomena.

Applied Mechanics doi: 10.3390/applmech6020036

Authors: Alfredo Márquez-Herrera

This work presents a novel, compact (six pieces), low-cost (<$500 USD), and easy-to-manufacture metallography mounting device. The device is designed to produce high-quality polymer encapsulated samples that rival those obtained from commercial equipment ($5000–$10,000 USD). Utilizing the House of Quality (HoQ) framework within Quality Function Deployment (QFD), the device prioritizes critical customer requirements, including safety (validated via finite element method, FEM), affordability, and compatibility with standard hydraulic presses. FEM analysis under 29 MPa pressure revealed a maximum Von Mises stress of 80 MPa, well below the AISI 304 stainless steel yield strength of 170 MPa, yielding a static safety factor of 2.1. Fatigue analysis under cyclic loading (mean stress σm = 40 MPa, amplitude stress σa = 40 MPa) using the Modified Goodman Criterion demonstrated a fatigue safety factor of 3.75, ensuring infinite cycle durability. The device was validated at 140 °C (413.15 K) with a 5-min dwell time, encapsulating samples in a cylindrical configuration (31.75 mm diameter) using a 200 W heating band. Benchmarking confirmed performance parity with commercial systems in edge retention and surface uniformity, while reducing manufacturing complexity (vs. conventional 100-piece systems). This solution democratizes access to metallography, particularly in resource-constrained settings, fostering education and industrial innovation.

Applied Mechanics doi: 10.3390/applmech6020035

Authors: Mohamed Semlali Omar Al-Mansouri Christoph Mahrenholtz

This paper focuses on the behavior of anchor channels in the event of fire. The contribution of this project lies in the necessity coming from the market to study the fire resistance of anchor channels more thoroughly, considering the modes of failure to which they are subjected. The aim of this paper is to transform the method based on tests into a numerical method that allows calculation of the fire resistance at any time under fire conditions, for all fire scenarios (whether it is a standard fire or using performance-based design approaches). A 3D transient thermal model was developed using ANSYS 19.1 to determine the thermal distribution of anchor channels, simulated in uncracked concrete under ISO 834-1 fire conditions. Subsequently, a design model for steel-related failure modes under fire conditions was employed. The model consists of coupling the characteristic resistances of the anchor channel at ambient temperature with temperature-based reduction factors for steel-related failure modes to obtain the calculated fire resistances. The model was compared with fire test results available in the literature, and the comparison yielded satisfactory results, confirming its reliability and accuracy in capturing the relevant phenomena under fire conditions. The results of this research show that the model presents a good candidate to replace the current method of qualification of anchor channels under fire conditions.

Applied Mechanics doi: 10.3390/applmech6020034

Authors: João Paulo Silva Lima Raí Lima Vieira Elizaldo Domingues dos Santos Luiz Alberto Oliveira Rocha Liércio André Isoldi

A hyperparameter-optimized Kriging surrogate model was developed for the structural collapse behavior framework presented in this paper. The assessment is conducted on a stiffened panel subject to axial load and lateral pressure, typical of the deck structure of a bulk carrier ship. This behavior is characterized using nonlinear finite element analysis to determine the collapse response. The surrogate model’s hyperparameters were optimized using a Genetic Algorithm to achieve the best performance, and the trained framework can predict ultimate strength. By following this approach, the problem can be reformulated as a multi-objective optimization task. This framework involves associating the Kriging surrogate model with a multi-objective evolutionary optimization algorithm based on Genetic Algorithms to balance the trade-off between the weight and ultimate strength of the stiffened panel. The results confirm the applicability of the Kriging surrogate framework to predict the ultimate strength and assess the collapse analysis of the stiffened panels, ensuring accuracy through GA-based hyperparameter optimization.