Search Results (15,781)

In this paper, a low-cost manual micro- and nano-displacement adjustment mechanism is proposed, based on the principle of flexible hinge transmission and micro-displacement scaling. The manual micro- and nano-displacement platform consists of a micrometer input platform, a nano-output platform, a differential head, and a strain displacement sensor. Firstly, a micro-displacement reduction mechanism based on a flexible beam triangular mechanism and a compact asymmetric flexible beam guiding mechanism are proposed, and a theoretical model is established for static mechanical characteristics, such as the displacement reduction multiplier, guiding stiffness, maximum stress, etc., and this is analyzed and verified by finite element simulation. The software and hardware system of the strain displacement sensor is designed and developed, and the calibration experiments of the strain displacement sensor are completed. Finally, the micro-displacement reduction times, resolution, stability, repeat positioning accuracy, load capacity and travel of the manual micro–nano-displacement platform were analyzed and experimented. The results show that when the input range of the micrometer input platform is 0–1 mm, the travel of the nano-output platform is about 0–16 μm; when a differential head with a step resolution of 2 μm is used to input 2 μm micro-displacement, the minimum displacement output of the nano-output platform is about 35.4 nm; the theoretical and simulated values of the reduction multiple of the micro–nano-displacement are 57.29 and 56.69, respectively; the calibration experiment is performed by the self-developed strain sensors, and capacitive displacement sensors measured the reduction multiples of 57.74 and 62.67, respectively, with high consistency; the vibration range of the platform after the displacement adjustment is about ±30 nm, and the load of 0–300 g has less influence on the output characteristics of the platform. Full article

Large flange shafts are the core load-bearing and connecting components of high-end equipment, and their welding multi-physical fields directly affect the quality and service safety of the components. Traditional experiments and finite element methods suffer from long cycles and low efficiency, which can hardly meet the demand for rapid prediction. Aiming at the fast and accurate prediction of welding temperature, deformation and residual stress, this study combines thermal–mechanical coupled finite element simulation with machine learning to construct and compare a variety of prediction models. A dataset is built based on simulation data from 100 groups of process parameters. Overfitting is reduced through strategies including early stopping and dropout, and models such as MLP, RF, RBF-SVR, TabNet, XGBoost, and FT-Transformer are established and verified through 10-fold cross-validation. The results show that the MLP model performs best in the prediction of temperature, deformation and residual stress, and is in good agreement with the simulation values. The prediction errors of the peak temperature of the weld and base metal are below 5%, and the errors of deformation and residual stress are controlled within 10%. The average error of peak residual stress is about 6 MPa, and the deviation of most samples is less than 5 MPa. The RF model ranks second in accuracy, with an average error of about 6.5 MPa for peak residual stress, showing a satisfactory interpretability and engineering applicability. RBF-SVR and TabNet can meet basic prediction requirements. Under the small-sample condition in this work, XGBoost and FT-Transformer present relatively large errors and a weak generalization ability, making it difficult to achieve high-precision prediction. The MLP model established in this paper can effectively reproduce the evolution of welding multi-physical fields and supports the rapid prediction and process optimization of large flange shaft welding. The generalization ability and practical performance of the model can be further improved by expanding the dataset and experimental verification in the future. Full article

The applicability of two different joining processes for producing lap joints from high-strength steel sheets is investigated, reflecting their increasing use in advanced lightweight structures with demanding performance requirements. The work is primarily focused on the joining-by-forming process known as double-flush riveting, evaluated in two variants: one utilizing forged holes and the other employing machined holes. The performance of these two variants is compared with conventional fusion-based resistance spot welding using lap joints fabricated from 2 mm high-strength low-alloy S500MC steel sheets under varying geometric and process conditions, with support from finite element modelling. Results indicate that both double-flush riveting variants produce similar joint cross-sectional geometries, but the machined hole variant simplifies sheet preparation and eliminates the need for a progressive tooling system. Tensile lap-shear and peel test results reveal that double-flush riveted joints with forged holes exhibit superior strength, attributed to strain hardening in the forged regions. Furthermore, for nuggets and rivets of equivalent size, both double-flush riveting variants surpass resistance spot welding in terms of the mechanical strength of the final joints. These results suggest that double-flush riveting represents a promising alternative for assembling high-strength steel sheets in lightweight structural applications. Full article

Railway transport is increasingly promoted as a sustainable and low-carbon mode of transportation. However, track-induced vibration propagation remains a significant challenge, particularly in metro systems situated near residential areas, where vibrations can transmit through the infrastructure into nearby buildings, disturbing residents and damaging structures. This study aimed to evaluate the cause of the significantly different vibration impact on nearby buildings caused by two nominally identical adjacent slab tracks on a metro line in Austria. Controlled weight drop tests were carried out in both track directions, and accelerations were measured to characterize wave transmission and energy dissipation. The data were processed using frequency response functions and Short-Time Fourier Transform to extract time–frequency signatures, modal parameters, and propagation delays. A three-dimensional finite element model of the railway superstructure was then calibrated against the experimental modal properties and transfer functions and used to simulate cracking or stiffness loss in the sleeper–slab region. The simulations reproduced the observed increase in slab acceleration and underground strain energy, linking the anomalous vibration transmission to hidden stiffness loss rather than to global design differences. Overall, the study demonstrates that combining impact testing, advanced signal processing, and calibrated finite element modelling provides an effective framework for diagnosing track defects and guiding the design and maintenance of more sustainable, low-vibration urban rail infrastructure. Full article

This study investigates the effects of an arch rib inclination angle and loading scenario on the elasto-plastic stability of steel basket-handle arches to support bridge design. A parametric finite element analysis was performed on 48 models, with inclination angles ranging from 0° to 15° under three vertical loading conditions: uniformly distributed (V), transversely eccentric (V₁), and longitudinally eccentric (V₂). A nonlinear analysis was conducted using the arc-length method. The results indicate that the ultimate bearing capacity is highest under loading V, followed by V₁ and V₂, irrespective of the inclination angle. The initial stiffness increases monotonically with inclination in all cases. Under V, the capacity peaks at a 10° inclination before declining, with a corresponding transition from out-of-plane to in-plane buckling at this critical angle. Under V₁, out-of-plane buckling dominates, and the capacity fluctuates slightly before increasing with the inclination. Under V₂, in-plane antisymmetric buckling prevails, and the capacity decreases gradually as the inclination increases. Eccentric loading induces severe stress concentration and local buckling at the arch feet, accelerating global failure. It is concluded that an inclination angle up to 10° enhances elasto-plastic stability under symmetric vertical loading, whereas eccentric loading substantially reduces the capacity; therefore, symmetric and simultaneous loading on both arches is recommended during construction. Full article

Man-made hazards pose serious threats to the safety and preservation of heritage structures. With armed conflict becoming increasingly prominent, it is urgent to enhance our understanding of how these structures respond under extreme conditions to drive conservation strategies. The Citadel of Aleppo in Syria, placed on the List of World Heritage in Danger in 2013 due to the civil war, tragically exemplifies the vulnerability of cultural heritage in times of conflict. In such a framework, this study focuses on the Minaret of the Ayyubid Great Mosque of the Citadel of Aleppo as a representative masonry tower to investigate the effects of man-made threats. Based on a 3D finite element model built in the Abaqus/Explicit environment, blast scenarios associated with aviation bombs and human-borne improvised explosive devices (IEDs) were simulated. The Conventional Weapons Effects (CONWEP) model was used to assess the structural response to blast pressures, also as a function of charge size, standoff distance, and modelling parameters (mesh size, strain rate). This study’s outcomes provide insights into the potential damage caused by aviation bombs and IED attacks, advancing the understanding of the vulnerability of tower-like masonry structures to such hazards while also informing future conservation strategies. Full article

This paper examines the use of high-rigidity Tau-robots in friction stir welding, where process loads are very high. The rigidity of Tau-robots increases at the expense of the workspace. Therefore, the right configuration of the Tau-robot is sought to reconcile rigidity and workspace requirements. This is studied by use of kinematics, followed by static and modal analysis. In particular, by extending an existing kinematic model employing free vectors, the robot workspace was derived in non-dimensional parametric form and was then maximized through evolutionary optimization. However, finite element static and modal analysis that were carried out subsequently may prove, as in a case demonstrated here, that the optimized configuration may not withstand high loads, typically axial forces of 15 kN and torques of 80 Nm, and it may also be susceptible to forced vibrations in the typical spindle rotation range up to 3000 rpm. As a rectification measure, it was shown how a modified configuration by placing robot kinematic chain bases further apart and shortening robot links achieves higher rigidity, axial displacement being reduced by one or two orders of magnitude to below 1 mm and increases critical modal frequency 3 to 5 times depending on the workspace position, of course sacrificing part of the workspace, i.e., reducing it 3-fold to enclose welding lines in a rectangle of dimensions 700 × 800 mm. In the quest for the appropriate robot configuration desired dimensions of parts to be welded and available standard components are briefly considered, too. Full article

This study investigates the cyclic behaviour of demountable steel–concrete composite extended end-plate reduced web section (RWS) connections for the first time, aiming to facilitate post-seismic beam replacement. A validated high-fidelity finite element (FE) model was developed to analyse 285 FE models, evaluating response characteristics based on the Ibarra–Medina–Krawinkler model. Key parameters, including the influence of composite action over the web opening, web opening diameter, and end-distance, were considered. Findings indicate that RWS connections with medium to large web openings experience cyclic strength degradation while remaining compliant with American and European seismic standards. Additionally, bolted shear studs yielded a more stable and predictable contribution to the connection’s strength up to 5%, outperforming traditional welded studs in consistency. This research emphasises the importance of aligning web opening size and location with capacity design ratios between connection components for acceptable seismic performance, proposing specific web opening sizes and locations to enhance structural resilience. Full article

The seamless flatness roll is a critical inspection device in cold-rolled strip flatness control systems. Prolonged service causes cracks and scratches on the roll surface, while repeated grinding gradually removes the hardened layer, potentially rendering the roll unusable. To address the risk of thermal damage to internal sensors during the laser cladding repair of seamless flatness rolls, this study proposes a process optimization strategy using the Finite Element Method (FEM) and Response Surface Methodology (RSM). Focusing on an 820 mm roll, a regression prediction model for laser spot and internal component temperatures was constructed using a Box–Behnken design (BBD) based on an experimentally calibrated FEM model. Multi-objective optimization determined the optimal process parameters: laser power of 1.43 kW, laser radius of 3.73 mm, scanning speed of 23.45 mm/s, and overlap rate of 50.40%. Under these conditions, the average error between the predicted and experimental results was only 4.14%. The results confirm that the optimized process ensures the formation of a molten pool while maintaining internal components within safety thresholds, validating the feasibility of this non-destructive repair method. Full article

Background and Clinical Significance: Traumatic brain injuries (TBI), most frequently caused by falls, represent a major source of morbidity and mortality and pose significant challenges in forensic investigations, especially when events are unwitnessed or testimonies conflict. Despite advances in imaging and autopsy, reconstructing the mechanism of head trauma often remains impossible. The objective of this study is to assess how biomechanical modeling can support forensic practitioners by narrowing the range of plausible scenarios and strengthening evidence-based interpretation in complex medico-legal contexts, without seeking to establish legal causality or certainty. Case Presentation: This case report investigates forensic biomechanics as a decision-support tool using a combined multibody and finite element (FE) modeling approach. An initial set of twenty-five scenarios, derived from witness statements and investigative data, was reconstructed to simulate potential fall- and assault-related mechanisms. Multibody simulations with the human facet model were first performed to estimate head impact velocities and orientations. These parameters were then applied to an FE head model to evaluate tissue response. Conclusions: Skull fracture patterns and intracerebral von Mises stress distributions were analyzed and systematically compared with clinical, radiological, and autopsy findings. Although simulated stress magnitudes were generally lower than injury thresholds reported in the literature, several scenarios reproduced fracture propagation and intracerebral stress patterns consistent with the documented lesions, including corpus callosum involvement. This multidisciplinary approach highlights the growing role of biomechanics in forensic investigations and forensic anthropology. Full article

This research explored the performance of steel fiber concrete-filled stainless-steel tube columns stiffened with embedded carbon steel T-sections with various steel fiber ratios under biaxial bending conditions. A numerical parametric analysis was adopted, using finite element modeling with Abaqus CAE/2021 to evaluate the effects of the fiber ratio (ranging from 0% to 1.5%) on the load-bearing capacity and deflection behavior of columns. In addition, the compressive strength of concrete ranged between 45 and 65 MPa. An increase in the fiber ratio led to a substantial improvement in the ultimate load-bearing capacity (up to 24%), a reduction in deflection (of approximately 49%), and an improvement in column ductility, which were obtained at 1.25% fiber content. The addition of steel fibers enhanced column performance, and energy absorption improved by up to 27% compared to specimens without steel fibers. Experimental validation demonstrated improved accuracy in terms of behavior and predicted models. The conclusions of this work provide valuable design insights enabling the adaptation of the overall column system under complex loading scenarios. Full article

Concrete-filled steel tubes (CFST) exhibit superior axial performance compared with hollow steel tubes due to the confinement interaction between steel and concrete. Understanding how geometric and material parameters influence this enhancement is essential for rational composite design. In this study, a three-dimensional finite element model is developed in ABAQUS to investigate the monotonic axial behavior of steel tube stub columns with and without concrete infill. The model incorporates geometric imperfections, nonlinear constitutive laws, and a contact-based steel–concrete interface, and is validated against published experimental results. A parametric study is then conducted by varying the diameter-to-thickness ratio, steel yield strength, and concrete infill condition. The axial load–displacement responses, stress evolution, and damage development are examined, and two quantitative indices are introduced to evaluate performance: the load enhancement factor associated with concrete confinement and the deformation capacity ratio. The results show that concrete infill significantly improves axial capacity and deformation stability, while the effectiveness of confinement decreases with increasing section slenderness. Higher steel strength increases peak load but alters the post-peak response depending on tube thickness. The findings provide numerical evidence for optimizing tube geometry and material combinations in CFST stub columns under axial compression. Full article

This study investigates the wind-resistant configuration of a seven-row single-span double-layer cable-supported photovoltaic (PV) array through conducting systematic analysis of the interference effect. Wind tunnel pressure measurement tests were conducted on a rigid model to obtain the wind force coefficients and torque coefficients under different wind directions. The time histories of wind pressure obtained from the tests were imported into a finite element (FE) model to calculate the vertical displacement and torsional angle responses. The wind-induced responses of different configurations with varying quantities and arrangements of longitudinal connections and wind-resistant cables were analyzed. The results indicate that in the case of head-on wind, wind force is the most unfavorable, and the correlation between wind force and torque is relatively low. In the case of oblique incoming flow, torque is the most adverse, and the correlation between wind force and torque increases. Directions of vertical displacement are opposite in windward and leeward wind scenarios, but directions of torsion angle remain consistent. Overall, the wind-induced responses at mid-span are greater than those at the edge, and the first-row response is more significant than that of the subsequent rows. The wind-induced vibration under windward flow conditions is more adverse when compared to that under leeward flow conditions. However, the downstream adverse interference effect caused by leeward incoming flow is more prominent. Based on the comprehensive analysis of wind loads and wind-induced responses, the whole structure is divided into three zones, namely, wind-induced response control zone, local wind pressure control zone, and wind effect transition zone. A wind-resistant configuration with longitudinal connection arrangements considering both safety and economic benefits is proposed, which provides a reference for the wind-resistant design of similar structures. Full article

In this paper, high-strength high-nitrogen steel Cr₁₈Mn₁₅ was fabricated using centrifugal casting. High-temperature tensile tests were subsequently performed on the centrifugally cast material. Based on the dynamic material model (DMM), power dissipation and instability maps were constructed for the steel. The results revealed that the optimal processing conditions for Cr₁₈Mn₁₅ are within a temperature range of 940 °C to 980 °C and a strain rate range of 0.001 s⁻¹ to 0.01 s⁻¹. Flow instability was observed primarily under high strain rate conditions (1 s⁻¹) at a lower temperature of 900 °C. Four constitutive equation models were established based on the experimental results, and the prediction accuracy was assessed by calculating their average absolute relative errors (AAREs) and correlation coefficients (r). It was found that the Modified-JC constitutive model could simultaneously take care of both accuracy and simulation convergence with an AARE of 17.823 and Pearson’s correlation coefficient (PCC) of 0.968. For the practical application of Cr₁₈Mn₁₅ high-nitrogen steel, a three-layer composite tube forming and a continuous rolling equipment were developed. The rolling and spreading process was simulated using finite elements, and the stress field, strain field, and temperature field in the spreading process were analyzed to determine the following optimum process parameters of the alloy: a temperature of 950 °C, a processing line speed of 1 m/s, and a preheating temperature of 200 °C. Full article

This research investigates the colonnade of Tomb 7 at the UNESCO World Heritage site of the Tombs of the Kings in Paphos, Cyprus. Specifically, a multi-drum column located at the south-east corner of the tomb is examined from both geometric and structural perspectives. Being the only standing element to support the entablature on that side of the tomb, the column is crucial for maintaining the structural stability of the monument. Numerical structural analyses are performed on the column via the finite element method (FEM), supported by close-range recording techniques—particularly terrestrial laser scanning (TLS)—to generate finite element (FE) models. Several modelling strategies capable of converting point cloud data into reliable structural models are developed and compared with the aim of identifying the most effective and cost-efficient approach. Each method is analyzed in detail to evaluate its workflow, assumptions, strengths, and limitations in the context of heritage structures with complex irregular geometries. Linear static and dynamic analyses are performed on five different FE models to assess the column’s mechanical response and to understand how differences in geometric representation affect the structural behaviour. The results indicate that all approaches adequately capture the general structural response. The comparison of the different modelling strategies highlights the trade-offs between geometric accuracy, computational efficiency, and practical usability. These outcomes indicate the potential and the current limitations of exploiting point cloud data for structural analysis and contribute to the development of more robust and accurate scan-to-FEM methodologies for the conservation and assessment of cultural heritage structures. Full article