Search Results (15,941)

During circumferential tensioning of prestressing strands in U-shaped aqueducts, longitudinal tensile stresses may develop and impair crack resistance. Most existing studies rely on three-dimensional finite element (FE) simulations. Although accurate, FE modeling is time-consuming and unsuitable for rapid scheme evaluation during construction. To overcome this limitation, the U-shaped aqueduct was first simplified as a cylindrical shell and the feasibility of this idealization was verified. An approximate analytical solution was then derived from cylindrical shell theory to predict the longitudinal stress induced by circumferential prestressing. Practical factors, including non-uniform wall thickness, non-equidistant strand spacing, and strand positional deviations, were incorporated to improve engineering applicability. FE results confirm good agreement, with RMSE of 0.055–0.169 MPa and NRMSE of 2.3–19.6%, where the upper bound occurs only in localized regions. The method was further applied to an engineering project to optimize the tensioning scheme. With a rational interval-tensioning procedure, the peak longitudinal tensile stress was reduced by 31.6%. Overall, the proposed approach enables rapid stress estimation and supports preliminary screening and optimization of circumferential tensioning schemes. Full article

In the vehicle electrification sector, the precise and reliable control of e-motors is of the utmost importance for ensuring the efficient and safe operation of the whole electric vehicle drivetrain. Specifically, the assessment of the absolute rotor position of the permanent magnet-based synchronous motors is necessary for precise e-motor control, which is strongly determined by the precision of the sensing device used for the absolute rotor position assessment. Magnetic rotational position sensing devices/encoders are predominantly used in the automotive sector. The accuracy of a magnetic-based rotational position sensing device can be affected by defects/errors which may occur during its manufacturing and/or assembly process. These defects may in turn affect the accuracy of the e-motor’s control and operation. The primary objective of this study was to numerically and experimentally design and investigate the accuracy of a magnetic-based off-axis rotational position sensing device intended for the control of a new permanent magnet e-motor, which was developed for a two-wheeler electric vehicle drivetrain. First, a 3D parametric numerical model of a magnetic rotational position sensing device mounted on the motor shaft was built by virtue of the finite element method (FEM). Based on numerical simulations, the appropriate dimensions of the magnetic ring were determined and the possible errors which may have occurred during its manufacturing process have been numerically imposed and analyzed. Second, the rotor position sensing device was prototyped based on the recommendations obtained with the 3D FEM model. Finally, the accuracy of the designed rotational position device was then experimentally assessed by comparing it to a standardized end-of-shaft rotational position encoder. To evaluate the influence of the possible errors on the e-motor rotor position measurement, the output characteristics of the motor torque as a function of its rotational speed of a real permanent magnet e-motor were experimentally assessed using two different rotational position devices. Based on the numerical end experimental results, we identified the manufacturing errors of the magnetic ring and analyzed their influence on the resulting output characteristics of the e-motor. The results revealed that the magnetic ring eccentricity and its magnetization process could affect the accuracy of the e-motor’s output torque characteristics. Full article

Tactile sensing is an important perceptual modality that enables robots to understand human contact behaviors. Estimating the fingertip contact angle based on tactile pressure distribution provides a simplified representation of the finger’s contact configuration and supports tactile-based perception in human–robot interaction. However, the relationship between tactile pressure distributions and fingertip contact configuration remains insufficiently understood. In this study, a simplified contact mechanics model was employed to investigate the relationship between tactile pressure characteristics and fingertip contact conditions. Theoretical analysis indicates that both the contact area and the contour dimensions of the pressure distribution are influenced by the contact angle and contact force, with varying sensitivities in different directions to these factors. Based on this theory, simplified finite element modeling of the fingertip and multi-subject experiments were conducted. The deformation behavior of the contact region under different contact angles and contact forces was analyzed. The experimental results were generally consistent with the theoretical analysis. Furthermore, contour descriptors were extracted from the tactile pressure distribution to establish a relationship model for estimating the fingertip contact angle, and the model’s accuracy was analyzed. The experimental results indicate that the extracted contour features exhibit systematic variations with contact angle, and the proposed method achieves a mean absolute error (MAE) of 2.73° and a root mean square error (RMSE) of 7.25°. These results demonstrate that tactile pressure contours provide an effective and computationally efficient cue for estimating fingertip contact configuration. This approach may help robots understand human behavior and has potential applications in human–robot interaction and robotic grasping. Full article

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. Full article

With Aligned Formable Fibre Technology (AFFT^™), fibers are reformatted into highly oriented epoxy prepreg tapes, enabling the structural reuse of recycled composite waste. The present study investigates whether discontinuous fiber laminates produced with AFFT^™ can be characterized and optimized with the same finite-element workflows long established for continuous fiber composites and whether the resulting structures meet demanding stiffness targets. Initially, various manufacturing methods were adopted, including vacuum bagging, compression molding at 7 bar to simulate autoclave conditions, and compression molding at 90 bar, comprising the three most reasonable manufacturing processes for AFFT^™ laminates. Experimentally measured orthotropic properties were introduced into a finite-element model representing an idealized bicycle top tube, which was chosen as a case study. A genetic algorithm screened candidate stacking sequences, minimizing the combined bending-and-torsion deflection. The best lay-ups reduced deformation by more than 30% compared to a quasi-isotropic baseline, showing that well-oriented short fibers can significantly contribute to the stiffness of composites. Tubes produced with the optimized lay-up were tested in three-point bending tests, and the measured stiffness matched simulations within 5%. These results confirm a key point for sustainable engineering: despite the absence of continuous fibers, conventional simulation strategies accurately predict the performance of AFFT^™ laminates and can be used as the basis for effective genetic optimization. This validation is significant: it enables the design of stiff, high-performance structures from recycled materials using established, cost-effective methods. By proving that optimization strategies developed for traditional continuous fiber composites apply to AFFT^™, this study offers a trusted and accessible pathway to scale circular economy solutions in next-generation composite products. Full article

One of the most critical aspects of design for an analyst or designer is understanding the service loads that a system or component will experience. In a standard finite element (FE) analysis, the service load history is applied to the FE model to generate the corresponding history of stresses and strains, which are necessary for further evaluations. However, for components operating in complex environments, accurately measuring or predicting the service load history can be particularly challenging. Instrumenting a prototype with load transducers is often an expensive and time-consuming process and, most importantly, may physically alter the component, changing its mass, stiffness, and load path, causing discrepancies between the measured and actual loads. In this context, this paper presents a load identification method, enhancing the methodology behind the load identification theory and reducing the uncertainties inherent in the standard approach, primarily due to the placement, number, and orientation of strain gauges. Full article

This work presents a finite element investigation of the thermo-mechanical response of a SiC-based power module subjected to spatially non-uniform thermal gradients during active power cycling. The multilayer package, including die, solder, and encapsulant, was modeled by elastoplastic constitutive laws to capture stress and strain evolution in time and space. Two scenarios were considered: a time–space variability with fixed gradients (an initial non-uniform temperature distribution was uniformly varied in time) and a time–space variability with time-dependent gradients (an initial non-uniform temperature was non-uniformly varied in time). Results highlight critical stress concentrations at the SiC/solder interface, with plastic strains up to 5% in the solder. This study underlines the importance of transient gradient modeling for reliability assessment and fatigue life prediction of power modules. Full article

Background/Objectives: This finite element analysis (FEA) assessed stress distribution in the tooth and dentin within an intact periodontium under 4 N of force and five orthodontic movements (intrusion, extrusion, rotation, tipping, and translation), using four failure criteria commonly used in numerical dental studies. Secondly, differences between brittle- and ductile-like failure criteria were found, and the most accurate criterion was determined. Additionally, movements more prone to inducing external orthodontic root resorption were assessed. Methods: Using nine 3D models of the second lower premolar, 180 numerical simulations were performed. The models were anatomically accurate based on CBCT scans. FEA employed the brittle-like Maximum Principal (MaxP), Minimum Principal (MinP), and ductile-like Von Mises (VM) and Tresca (T). Results: The results showed that tipping was less prone to external orthodontic root resorption than translation, extrusion, intrusion, and rotation, which showed areas of high stress concentration in the cervical third of the root. High-stress areas were visible only when the dentin-pulp-NVB components were separately analyzed, and not when the entire tooth structure was assessed. Only by correlating the qualitative with the quantitative results could the difference between brittle-like and ductile-like failure criteria be seen. Conclusions: In total, 4 N of applied orthodontic force can induce limited islands of external orthodontic root resorption (intrusion–extrusion on the vestibular side, rotation–translation on the lingual and distal–lingual sides). The ductile-like failure criteria maintained the accuracy of the results across all FEA simulations, while the brittle-like criteria showed various quantitative and qualitative inconsistencies. Full article

The growing demand for lightweight and cost-effective vehicular armor systems has driven the development of hybrid multilayer architectures capable of improving ballistic resistance while reducing structural mass. This study evaluates the ballistic performance of a functionally graded aluminum–Kevlar–cabuya fiber composite system designed for vehicle door protection. A combined experimental–numerical framework was implemented, integrating ballistic testing according to NIJ 0108.01 and STANAG 4569 Level 1 standards with explicit dynamic finite element modeling based on the Johnson–Cook constitutive formulation for AA5083-H32. The multilayer configuration (25 mm aluminum/15 mm Kevlar 29/15 mm treated cabuya composite) successfully resisted 9 × 19 mm and 5.56 × 45 mm FMJ threats without complete perforation. Numerical simulations predicted a maximum back-face deformation of 52.75 mm under 9 mm impact, showing strong agreement with the experimental measurements (mean ± SD, n = 3). Post-impact microstructural analysis revealed a sequential energy dissipation mechanism governed by plastic deformation of the aluminum layer, Kevlar fibrillation and fragment retention, and controlled micro-cracking within the treated cabuya backing layer. With an areal density of 140.87 kg/m², the system achieved a 19% weight reduction compared with conventional steel-based solutions. These results demonstrate the structural-scale feasibility of integrating treated cabuya fiber composites as active energy redistribution layers in certified hybrid vehicular armor systems. Full article

The pile foundations of hydraulic crossing structures are vulnerable to scour, which can significantly reduce bearing capacity and threaten structural safety. In existing studies, simplified assessment approaches have mainly been used, such as pre-defined scour holes or instantaneous scour, which cannot fully capture the progressive development of scour holes. In addition, there are limited systematic comparisons of the lateral responses of piles with different cross-sectional shapes under scour conditions. To address these issues, a series of finite element simulations were carried out in this study and the numerical model was validated against centrifuge test results. The “model change” technique was then used to simulate the progressive development of general scour. Circular and square piles with equal cross-sectional areas were considered under scour conditions, and the effects of instantaneous and progressive scour were compared at the same depth. The load–displacement response, pile–soil deformation and failure mode, bending moment, and pile displacement were analysed, with the results showing that square piles exhibited a higher lateral bearing capacity than circular under both no-scour and two types of general scour conditions. Scour altered the pile–soil failure mode and reduced the extent of the wedge-shaped failure zone around the pile, with that induced by square piles being larger than that induced by circular. At the same scour depth, the difference between the effects of instantaneous and progressive scour on lateral bearing capacity was not significant. The results indicate that the pile cross-sectional shape is a key factor affecting scour resistance and that square piles show a relative advantage. The findings provide useful guidance for the cross-sectional selection and lateral bearing capacity assessment of pile foundations in scour-prone areas. Full article

Scalability of the original test design for the box assembly with removable component (BARC) structure is of interest in the field of experimental structural analysis. As complex structures become increasingly difficult to test experimentally the larger they become, it is a common test practice to use a scaled-down representative model to understand the characteristics of these systems. For complex structures with non-rigid boundary conditions, there exists a gap in understanding the effects of scalability and welding. To gain a better understanding of the outcomes of this phenomenon, the dynamical effects of upscaling the dimensions of the BARC structure are analyzed. Three variations of the BARC are investigated experimentally and computationally, namely, the original BARC system, the BARC system upscaled at 1.5 times the size of the original model, and the BARC system upscaled at two times the size of the original model. The original BARC is tested to investigate the properties of the predetermined boundary conditions. Because the upscaled BARC systems are manufactured using welding, an investigation of the variability of results due to welding imperfections is conducted to evaluate its effects on the vibrational properties of the systems. The dominant resonant frequencies of the three systems are identified through an impact hammer test. The results are then compared to those obtained through finite element analysis, in which both datasets show agreement. In general, as the BARC system is upscaled, the resonant frequencies decrease without inducing mode switching for the selected boundary conditions, indicating that the larger systems are less rigid. To understand the trends of nonlinear softening/hardening and nonlinear damping, forced vibration experiments conducted in the form of true random and controlled stepped-sine excitations are performed. The results show that, in general, as the BARC system is upscaled, changes in the nonlinear properties of the system are induced. With regard to the effects of using welding to manufacture BARC systems, the results prove that variations in welding can lead to non-negligible variations in the vibratory responses of the BARC system. Additionally, several types of harmonic vibrational testing are investigated to understand the physics behind their varied responses. Overall, this work shows that upscaling the BARC system can be beneficial to researchers who require a less rigid system for investigations and that manufacturing of BARC systems by welding can be a cost-effective alternative to subtractive manufacturing. Full article

Background and Objectives: Determining the mechanical stability of osteosynthesis in pertrochanteric fractures remains a critical challenge in orthopedic biomechanics. The aim of this study was to develop a mathematical model for quantifying the stability of osteosynthesis and to establish criteria for its evaluation under physiological loading conditions. Materials and Methods: A mathematical model describing the biomechanical behavior of a proximal femur with a pertrochanteric fracture stabilized using a cephalomedullary nail (CMN) was developed. The model integrates force equilibrium, stress–strain relationships, and loading conditions representative of early functional rehabilitation. The theoretical framework was implemented in MATLAB/Simulink R2025b and complemented by finite element analysis to determine stress distribution, deformation patterns, and stability-related parameters of the bone–implant system. Results: The developed mathematical model enabled a quantitative assessment of osteosynthesis stability through the evaluation of key mechanical indicators, including displacement, stress distribution, and safety factor within the fixation system. Critical stress zones in the implant and surrounding bone were identified, allowing analysis of load transfer mechanisms. Finite element simulations showed that improved fixation mechanics reduced peak implant stresses, limited displacement at the fracture site, and increased the safety factor of the fixation construct, resulting in a more uniform load distribution in the surrounding bone and enhanced overall stability of the osteosynthesis system. Conclusions: The proposed mathematical model provides a systematic approach for determining the stability of osteosynthesis in pertrochanteric fractures. It offers a theoretical basis for optimizing implant design and fixation strategies, with potential applications in preclinical evaluation and surgical planning. Full article

With the shift of oil and gas exploitation to deep seas, the 35 kV high-voltage electric slip ring in Single-Point Mooring (SPM) systems faces critical challenges of insulation failure and thermal failure, threatening operational safety. This study aims to investigate its insulation strength and temperature rise characteristics. A three-dimensional electric field model and a magnetic–thermal coupling model considering the skin effect were established using the finite element method (FEM). Simulations were conducted under four high-voltage configurations and various high-current operating conditions, followed by AC breakdown tests and high-current temperature rise experiments for validation. The results show that the maximum electric field (up to 19.53 kV/mm) concentrates at the inlet polytetrafluoroethylene (PTFE) bushing, which is the insulation weak point. The maximum temperature rise at the center ring can be predicted by a power-law model. Moreover, simulation results agree well with experimental data, confirming the reliability of the computational studies. This work provides a theoretical and experimental basis for the optimal design and safe operation of high-voltage slip rings in offshore SPM systems. Full article

This study systematically investigated the bearing capacity and failure mechanisms of ultra-high-performance concrete (UHPC) pipe jacking structures using three-edge bearing tests and numerical simulations. Full-scale double-layer reinforced pipes had an inner diameter of 2.5 m and wall thicknesses of 180 mm (P1) and 200 mm (P2). The tests showed that the failure process can be divided into four stages: elastic deformation, crack propagation, reinforcement yielding, and ultimate failure. Increasing the wall thickness significantly improved performance: P2 had a cracking load 52.73% higher and an ultimate bearing capacity 5.7% higher than P1, with better deformation resistance and crack control. A theoretical model considering the plastic hinge mechanism at the pipe crown was developed, treating the three-edge load as an equivalent distributed plate load. The calculated results agreed well with experimental measurements. An ABAQUS finite element model successfully reproduced the full mechanical response from initial loading to failure. Parametric analysis indicated optimal performance at a hoop reinforcement ratio of approximately 1.4%. Even at 0.6%, the ultimate bearing capacity reached 367 kN/m, meeting current design code requirements. This study is novel in conducting full-scale UHPC pipe jacking tests, proposing a theoretical model accounting for crown plastic hinges, and establishing a finite element method that reproduces the entire failure process. Optimizing wall thickness and hoop reinforcement can enhance structural safety and durability, providing guidance for the design and engineering of pipe jacking structures. Full article

This paper presents a computational study of wave–bathymetry and wave–structure interaction problems using advanced numerical techniques based on high-fidelity, two-phase Navier–Stokes (TpNS) flow and reduced-order, fully nonlinear potential flow models. For high-fidelity simulations, the TpNS equations are discretized using the finite-element method, with free-surface evolution captured through a hybrid level-set (LS) and volume-of-fluid (VOF) formulation. A monolithic, phase-conservative LS equation is introduced to mitigate mass loss and interface smearing, combined with a semi-implicit projection scheme. Hydrodynamic forces are resolved using a high-order, phase-resolving cut finite-element method (CutFEM), which enables the representation of complex solid geometries within a fixed background mesh. An equivalent polynomial of Heaviside and Dirac distributions ensures accurate evaluation of surface and volume integrals. Hence, no explicit generation of cut cell meshes, adaptive quadrature, or local refinement is required. For reduced-order modeling, a fast regularized boundary integral method (RBIM) is employed to solve the fully nonlinear potential flow. Singular and near-singular integrals are treated using a subtract-and-addition technique based on auxiliary functions derived from Stokes’ theorem, allowing direct application of high-order quadrature without conventional boundary element discretization. An arbitrary Lagrangian–Eulerian (ALE) formulation is adopted to enforce free-surface boundary conditions while avoiding excessive mesh distortion. The proposed approaches are applied to investigate highly nonlinear wave transformation over complex bathymetry and wave-induced dynamics of floating structures, including eddy-making damping effects. Numerical results are validated against experimental measurements. These two modeling approaches represent complementary levels of physical fidelity and computational efficiency, and their systematic comparison clarifies the trade-offs between computational accuracy, efficiency, and cost for practical marine problems. Full article