Search Results (349)

In this study, an elastoplastic finite element (FE) contact model was developed to evaluate the plastic deformation of a surface induction-hardened tapered roller bearing used in wind turbines, incorporating depth-dependent material properties and heat treatment-induced residual stress distribution. The validity of this model was confirmed by comparing the calculated plastic deformation with measured profiles from static compression experiments. The results show that the residual stresses generated by induction hardening have a significant influence on the elastoplastic behavior of bearings. Based on this model, a parametric analysis was performed to investigate the effects of surface hardening depth (SHD), contact pressure, and residual stress on surface plastic deformation. Empirical formulas were developed to predict surface plastic deformation and evaluate material yielding for surface-hardened tapered roller bearings, thereby preventing excessive deformation during service. This allows for the rapid estimation of the maximum plastic deformation for different hardening depths and provides an efficient approach for assessing the yielding risk. Full article

TC4DT (ELI) is a damage-tolerant titanium alloy characterized by high fracture toughness and slow crack propagation rates, and is, therefore, considered one of the standard materials for model fasteners in modern equipment. However, its high yield strength leads to excessive tool wear and forming defects. This paper presents a complete FE simulation framework to investigate the thread-rolling process of TC4DT(ELI) bolts M16 × 1.5. Using the actual geometries of the workpiece and rollers, an elasto-plastic three-dimensional finite element model was built in ABAQUS/Explicit to perform verification simulations, with the theoretical blank diameter and forming force as the reference benchmarks. The simulation results agreed well with the actual industrial data. This study carried out single-factor analyses of the effect of three important process parameters—the roll speed, friction coefficient, and initial temperature—on the resulting stress–strain distribution, forming force, and thread formation depth. A modal analysis was performed in ANSYS Workbench to check the structural integrity and avoid resonance while operating. According to the results, the optimized parameters decreased the maximum forming force by 14.8% and improved thread filling. Compared with experimental data, the simulation error in the blank diameter was controlled within 1.2%. The present work, a reliable numerical underpinning for replacing expensive and time-consuming trial-and-error processes, forms a basis for high-performance titanium alloy fasteners and assists in the wider application of such fasteners in modern equipment and any advanced manufacturing industries. Full article

This study investigated the development of a perlite waste-based geopolymer for stabilizing iron ore tailings byproduct (IOTB) for geotechnical applications. Mixtures containing 70/30 and 80/20 proportions of byproduct and geopolymer were produced using perlite waste as the precursor and NaOH as the alkaline activator through the one-part method. Raw and geopolymer-stabilized IOTB, air-cured for 7, 14, and 28 days, were evaluated by ICP-OES, XRF, pH, geotechnical characterization, compaction, permeability, SEM, and consolidated drained triaxial tests under confining stresses ranging from 250 to 2000 kPa. The selected mixture presented a maximum dry density of 1.8 g/cm³ and optimum moisture content of approximately 14%. XRD results indicated sodium aluminosilicate phases associated with geopolymerization, with mechanical characteristics comparable to feldspar-type structures, while the pH increased from 6.5 to 12.5. Triaxial tests indicated that elastoplastic behavior persisted regardless of the geopolymer addition; however, SEM images confirmed matrix–particle bonding at grain contacts without significant pore filling. The cohesive intercept increased from 0 kPa in the IOTB to 89.1 kPa and 179.2 kPa after 14 and 28 days of curing, respectively, while the friction angle showed a slight increase of up to 7.7%. Deviatoric stress at failure and energy absorption capacity also increased with curing time. Hydraulically, the permeability coefficient remained within the same order of magnitude (10⁻⁴ cm/s), varying from raw IOTB of 2.73 × 10⁻⁴ cm/s to 3.28 × 10⁻⁴ cm/s after 28 days. These results demonstrated that geopolymer stabilization enhanced mechanical performance without compromising drainage capacity, representing a technically viable and socio-environmentally sustainable solution. Full article

As the most prevalent type of existing building in China, masonry structures are susceptible to cracking due to the low tensile strength of the masonry material. In the event of a sudden, strong earthquake, they are highly prone to brittle collapse, leaving occupants little time and space to escape. Based on this, combining the advantages of the elastoplastic mechanical theory and the nonlinear finite element (FE) method, this study adopts different modeling methods: integral modeling (IM), contact element discrete modeling (CEDM), spring element discrete modeling (SEDM), and co-node discrete modeling (CNDM). FE models of unreinforced masonry walls (UMWs) are established, respectively, and a monotonic pushover mechanical performance analysis is carried out. The accuracy of the adopted modeling methods is verified against existing test results for UMW specimens. Through parametric analysis of aspect ratios (0.5, 0.75, 1.0, and 1.25), axial compression ratios (0.1, 0.3, 0.5, 0.7, and 0.8), and mortar strengths (M5, M7.5, and M10), the characteristic mechanical performance factors of UMWs are determined. A novel strength index is proposed to discriminate between failure modes and elucidate the damage mechanism of UMWs. The results indicate that the ultimate load and its corresponding displacement change systematically with variations in aspect ratios, axial compression ratios, and mortar strengths. Furthermore, integrating stress cloud maps with the proposed strength index provides a quantitative basis for discriminating between flexural and shear failure modes in UMWs. All four modeling methods can, to varying degrees, capture the pushover behavior of UMWs, and quantifiable selection schemes are provided to balance analysis accuracy and computational cost. The analytical methods and findings presented in this work can be applied to performance assessment, seismic design, and engineering practice of UMWs. 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

This study investigates the transient wheel–rail contact mechanics of welded joints in heavy-haul rails via a validated 3D finite element model, and analyzes the stick-slip behavior, dynamic response and elastoplastic characteristics in the base material zone, heat-affected zone and weld bead zone. Results show a distinct contact state transition from stick-slip in the base material to predominant slip within the welded zones, indicating higher wear susceptibility. Dynamic response analysis reveals the highest and lowest contact-point acceleration amplitudes in the base material and heat-affected zone, respectively, due to material heterogeneity. Plastic deformation consistently initiates at the rail surface, where stress and strain concentrate, establishing it as the primary site for damage nucleation. A systematic parametric study shows that plastic deformation can be effectively mitigated by increasing the yield strength and elastic modulus of the welded joint material, or reducing the wheelset velocity, unsprung mass and wheel–rail friction coefficient. In contrast, adjusting the primary suspension and fastener parameters exerts a negligible influence on plastic deformation control. These findings provide a mechanistic basis for optimizing the performance and maintenance of welded joints in heavy-haul rail operations. This study reveals the coupling law of multiple mechanisms among contact behavior, dynamic response and material failure during the damage initiation process of rail welded joints from the mechanistic perspective, which provides a theoretical basis for the structural optimization, condition assessment and maintenance of rail welded joints in heavy-haul railways. Full article

The formability of AA7021-T4 sheets under changing strain paths was investigated via a novel crystal plasticity model and associated experimentation. The motivation was to advance simulation tools for process design of limited-ductility 7xxx alloys, with important applications in the automotive industry. Pre-strains were applied in biaxial and plane-strain tension using Marciniak tooling, followed by uniaxial tensile testing to failure. Strain measurements were obtained by digital image correlation, while dislocation structures were characterized using high-resolution EBSD. A strain-gradient elasto-plastic self-consistent (SG-EPSC) model incorporating dislocation density-based hardening and backstress from geometrically necessary dislocations (GNDs) was employed to predict the stress–strain response and dislocation evolution. Results showed that pre-strains normalized by forming limit diagram (FLD) criteria produced comparable residual uniaxial tensile ductility, regardless of whether biaxial or plane-strain tension was applied, despite differences in absolute pre-strain levels. Both experiments and simulations revealed that GND density correlated with remaining ductility better than simple strain magnitude values. These findings indicate that AA7021-T4 retains greater formability under multiaxial strain path changes than expected from FLD-based considerations. The combined experimental–modeling approach demonstrates the value of incorporating microstructure-based variables, such as GNDs, into forming assessments of high-strength aluminum alloys, with implications for their potential use in automotive lightweighting development. 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

The complex coupling relationships among the thermal, mechanical, and electrical physical parameters of TiZrHf-based medium-entropy alloys represent a key factor restricting their practical applications under complex extreme environments. In this study, the thermo-mechanical-electrical coupling characteristics of TiZrHf and TiZrHfCu_0.8 medium-entropy alloys were systematically investigated using a self-developed experimental platform. The results demonstrate that TiZrHf and TiZrHfCu_0.8 alloys exhibit elastoplastic and superelastic-plastic compressive deformation behaviors, respectively, with both elastic modulus and ultimate strength decreasing monotonically with increasing temperature T. Electrical property measurements reveal that the electrical resistivities ρ of the two alloys range from 3 to 35 × 10⁻⁶ Ω·m. Notably, TiZrHfCu_0.8 possesses a lower resistivity that is independent of the test frequency f. Moreover, ρ increases with T but decreases with applied stress σ. At a frequency of 1 kHz, the real part of the relative dielectric constants ε_r of the alloys varies between −3.5 × 10⁸ and −0.5 × 10⁸ and increases with rising f, whereas the effects of T and σ on ε_r are opposite to those on ρ. Thermal property tests indicate that the thermal conductivities α of both alloys increase with T and eventually stabilize at 28.23 and 53.51 W·m⁻¹·K⁻¹, respectively, while the thermoelectric coefficients S are positively correlated with the heating rate, on the basis of comprehensive data analysis, multi-physical parameter (T, σ) dependent mathematical expressions for elastic modulus, strength, ρ, ε_r, α, and S were established, respectively. This work provides valuable insights into the material response mechanisms under complex service conditions, which are conducive to the optimization of alloy composition design and the promotion of their practical engineering applications. Full article

This study addresses the problem of traffic congestion in large cities caused by long-term repairs of underground utility networks. An innovative mobile overpass is considered, which combines the functions of a vehicle and a temporary bridge, allowing passenger cars up to 3.5 t to pass directly over repair trenches without detours. The research focuses on optimizing the placement of overpass supports relative to the trench edge to reduce soil deformation and prevent trench wall instability. A numerical methodology is developed in ANSYS Workbench that integrates finite element analysis of the soil-support system with parametric optimization using the nonlinear Drucker–Prager elastoplastic model. The soil parameters are obtained from oedometer compression tests (KPr-1M) and direct shear tests (PSG-2M) on clayey soils and then used to calibrate the numerical model. The optimization results show that the optimal distance from the trench wall to the overpass support is $L_{\min } = 2.78$ m, which is 13.5% greater than the initial design value. This modification reduces the maximum horizontal displacement of the trench wall by more than a factor of two and ensures compliance with the displacement criteria. Comparison between experimental and numerical compression curves yields an average deviation of 37.55%, with errors below 5% at higher stress levels, confirming that the Drucker–Prager model is suitable for engineering optimization of mobile overpass support placement on similar soils. The proposed methodology can be applied to the design and verification of temporary bridge systems operating above utility trenches in urban environments. Full article

To enhance the load-bearing capacity of conventional reinforced concrete (RC) columns and address the issue of longitudinal reinforcement buckling, this study proposes a novel composite column strengthened with small-diameter ultra-high-performance concrete-filled steel tubes (UHPCFST), in which the UHPCFST members replace the traditional longitudinal reinforcement. First, the mechanical behavior of UHPCFST was experimentally investigated. Results show that its stress–strain curve exhibits steel-like elastoplastic or strain-hardening characteristics after yielding. Subsequently, the axial compressive performance of the proposed column was studied through numerical simulation, with emphasis on the failure process, load–displacement response, and contribution of each constituent material at different loading stages. By comparing the longitudinal stress in concrete and the strain development in longitudinal reinforcement, steel tubes, and stirrups between conventional RC columns and the composite column, and by systematically varying parameters such as the steel ratio and the number of steel tubes, the influence of these parameters on the axial performance of the composite column was revealed. The results indicate that replacing longitudinal reinforcement with UHPCFST significantly improves the column performance. Compared to a conventional RC column with an equivalent reinforcement ratio, the proposed composite column exhibits an approximately 10% higher peak load capacity, a 182% increase in peak displacement, and a distinct biphasic response characterized by a double-peak pattern in its load–displacement curve. The first peak is contributed jointly by the surrounding concrete and the UHPCFST, while the second peak is mainly provided by the UHPCFST skeleton. This study offers a new perspective for improving the seismic resistance and load-carrying capacity of RC columns. Full article

Considering the impact of void damage on the mechanical properties of materials, based on the two-parameter yield criterion, combined with the associated flow rule and the upper bound theorem, the void volume fraction is introduced into the macroscopic yield function, resulting in a mesoscale damage model. Two material parameters in the model are defined using yield strength and Poisson’s ratio, respectively. The yield surface of the model is presented for different void volume fractions and Poisson’s ratios. Using the mesoscale damage model, combined with the positive flow rule, the constitutive relationship of the material is established, and an elastoplastic analysis is performed for axisymmetric plane stress problems. Under the Prager hypothesis, a set of differential equations is derived to solve the problem, yielding numerical solutions. The influence of void volume fraction on the stress field and displacement field is qualitatively discussed. The research results show that when the void volume fraction is constant, the closer to the void opening, the larger the absolute value of radial stress and displacement, and the faster the material flows, with the material reaching the yield state first. As the void volume fraction increases, both the absolute value of radial stress and displacement decrease relatively. In contrast, the change in circumferential stress is relatively small, but the patterns of the numerical result curves tend to be consistent. Full article

Existing macroscopic finite element models for electron beam welding (EBW) typically assume isotropic material behavior, often failing to accurately predict residual stresses induced by strong crystallographic textures. To address this limitation, this study established a sequential dual-scale coupled numerical model bridging micro-texture to macro-mechanics by combining the crystal plasticity finite element method (CPFEM) with thermal-elastic-plastic theory. Representative volume elements (RVEs) incorporating α and β dual-phase characteristics were constructed based on electron backscatter diffraction (EBSD) data from the TA15 weld cross-section. Through simulated tensile and shear calculations on the RVEs, homogenized orthotropic stiffness matrices and Hill yield constitutive parameters were derived and mapped onto the macroscopic model. Simulation results indicate that the proposed model maintains the prediction error for molten pool morphology within 16.3%, while effectively correcting the stress overestimation inherent in isotropic models. Specifically, it adjusts the peak longitudinal residual stress at the weld center from 800 MPa to approximately 350 MPa, significantly reducing the anomalous “M-shaped” stress distribution. By successfully capturing shear stress components, this work provides a high-fidelity computational approach for predicting complex stress states in welded joints, offering critical insights for structural integrity assessment. Full article

Intense thermo-mechanical coupling effects during cutting generate residual stress within the surface layer of a workpiece. This residual stress is a critical factor influencing the fatigue life, corrosion resistance, and dimensional stability of mechanical components, making its accurate prediction and control essential for improving product performance. To address the often generalized treatment of residual stress prediction modeling in existing literature, this paper presents a systematic review of recent advances in surface residual stress prediction for cutting operations. It details the formation mechanisms and significance of residual stress, focusing on four primary modeling approaches: empirical models based on experimental data, analytical models founded on metal cutting and elastoplastic theory, finite element models that simulate actual machining conditions, and hybrid models. A comprehensive analysis and comparison of these four model types is provided, summarizing their respective advantages and limitations. Furthermore, this paper identifies potential future research directions and development trends in residual stress prediction modeling, serving as a valuable reference for work in this field. Full article

Accurate measurement of material mechanics parameters is crucial for evaluating process quality and product reliability and is a major challenge in the development of 3D heterogeneous integration technology. Aiming to perform high-accuracy measurements of the elastoplastic nonlinear constitutive parameters of microelectronic materials using the nanoindentation testing technique, we take advantage of a neural network to construct a forward characterization model to characterize these response characteristic parameters for different materials, design an improved algorithm for obtaining a reverse iterative solution of the forward characterization model, and develop a material mechanics parameter measurement method to solve overdetermined equations using the least-squares method. This method was further improved by addressing the issues of algorithm stability and solution uniqueness, achieving high-precision and fast reverse solutions for elastoplastic constitutive parameters. The relative error of the material parameters is less than 3% (95% confidence interval), the maximum error is less than 8%, and the inversion convergence error of the key indentation response characteristic parameters is less than 0.1%. The difference between the measured material parameters and the theoretical model in the influence on the process stress of TCV (through ceramic via) products is verified through finite element simulation. Full article