Search Results (223)

Metal additive manufacturing (MAM) enables the fabrication of geometrically complex and high-performance components but is accompanied by steep thermal gradients, repeated thermal cycling, phase transformation, residual stress, and deformation. These effects can reduce dimensional accuracy, manufacturing stability, fatigue resistance, and service reliability. This review systematically examines residual-stress and deformation behavior in MAM from the perspectives of formation mechanisms, influencing factors, measurement and prediction methods, mitigation strategies, and service-related consequences. The temperature gradient, mechanical constraint, and phase transition mechanisms are discussed as quantitatively coupled rather than independent processes. Comparative attention is given to process-specific differences, alloy-dependent thermophysical and metallurgical behavior, multi-track and multi-material interactions, and complex geometries. Destructive and non-destructive measurement techniques are compared in terms of penetration depth, spatial resolution, uncertainty, and cross-validation. Thermo-mechanical finite element, inherent strain, analytical, reduced-order, machine-learning, physics-informed, and digital-twin approaches are evaluated according to accuracy, efficiency, transferability, and applicability. Mitigation strategies are further compared considering residual-stress reduction, deformation control, manufacturing cost, and mechanical-property retention. Finally, challenges associated with uncertainty quantification, service environments, post-machining stress redistribution, and closed-loop control are identified. This review provides an integrated framework for selecting measurement, prediction, and mitigation approaches for reliable and high-precision MAM. Full article

Seismic-resistant reinforcing steels (rebars) are indispensable for improving the safety and resilience of reinforced concrete structures subjected to earthquake loading. To perform effectively under such severe conditions, these steels must combine high strength with adequate ductility, toughness, and fatigue resistance. Achieving this balance depends on the control of the steel’s microstructure. In this context, microalloying with vanadium (V), niobium (Nb), and titanium (Ti) has become an effective strategy for controlling microstructural evolution through grain refinement, precipitation strengthening, recrystallization control, and phase transformation, therefore enhancing both monotonic and cyclic mechanical performance. Although the effects of microalloying and strengthening mechanisms in reinforcing steels are well documented, studies examining their combined influence on seismic applications remain relatively limited. This review therefore provides an integrated perspective by examining how alloy composition, thermomechanical processing routes, microstructural evolution, and strengthening mechanisms interact to determine the mechanical and fatigue performance required for seismic-resistant reinforcing steels. Rather than considering these aspects separately, this review focuses on the interactions between processing, microstructure, and mechanical behavior that determine the overall performance of reinforcing steels. This review also highlights the main scientific and technological challenges in the field, discusses the remaining knowledge gaps, and suggests future research directions for the development of next-generation seismic-resistant reinforcing steels. Full article

Ultra-supercritical (USC) steam turbines combine severe steam conditions with increasingly frequent start-up, shutdown, and load-following operations. Their main steam valves must preserve pressure boundary integrity, sealing, and rapid actuation while non-uniform heating, creep, cyclic plasticity, oxidation, wear, and contact redistribution alter component geometry. However, the relevant evidence remains fragmented across alloy development, component thermo-mechanics, valve aerodynamics, and lifetime monitoring. This short, mechanism-oriented review integrates these domains through a material structure–function framework in which deformation relative to assembly clearance governs jamming risk. It synthesizes evidence on heat-resistant body and surface materials, 9–12% Cr steel stability, weldability and repair sensitivity, and cold, warm, and hot start-up histories. It also evaluates creep–fatigue interaction, contact, flow-induced vibration, multi-physics modeling, validation, uncertainty, monitoring, and digital twins. The synthesis shows that neither peak equivalent stress nor steady-state temperature alone can establish functional reliability. Credible assessment requires temperature-dependent material data, realistic steam-side heat transfer, cyclic constitutive behavior, initial and residual clearances, manufacturing and assembly tolerances, state-dependent friction, uncertainty analysis, and corroborating plant or inspection evidence. The most consequential research needs are valve-level validation datasets, thermal contact testing, function-oriented life criteria, and uncertainty-aware digital twins that jointly inform materials, geometry, and transient operation. Full article

High-volume injection molding systems for plastic part production operate under severe thermo-mechanical loading repeated at high production rates. Therefore, premature breakage of hot-work tool steel core inserts directly interrupts production continuity and creates a recurrent maintenance problem. To address this failure mode, this study collected production inputs and failure evidence and established a reliable interpretation by linking computer-aided engineering simulations of the plastic injection molding process, structural FEA of the insert response, and cumulative fatigue assessment using a TMF-creep damage model. This integrated approach provides a comprehensive framework for failure root-cause identification and service-life prediction and improving insert durability in mass-manufacturing environments. Full article

To overcome the limitations of conventional homogeneous materials in floating photovoltaic (FPV) systems, this review critically examines advanced material-s design strategies and fabrication approaches that enable enhanced durability, reliability, and performance under coupled hydro-mechanical and environmental loading conditions. Although FPV systems provide a scalable solution to land scarcity, their long-term operation is challenged by wind–wave interactions, persistent moisture exposure, thermal cycling, and corrosion-induced degradation, and biofouling, requiring materials capable of accommodating spatially varying and interacting stressors. Functionally graded materials (FGMs) are explored as a promising solution, enabling continuous variation in the composition and microstructure to tailor local mechanical, thermal, and chemical properties within a single structure. Recent research highlights growing interest in additive manufacturing and gradient design, but limited focus on FPV and marine applications. Emphasis is placed on additive manufacturing as a key fabrication route for realizing complex gradient architectures with high precision and design flexibility. Recent advances demonstrate notable improvements in corrosion resistance, fatigue performance, and stress distribution, leading to the enhanced structural integrity and service life of FPV systems. The review further organizes FGM concepts within a design–process–property–performance framework and discusses their application in key FPV subsystems. This review further evaluates the role of multi-physics modelling and digital twin frameworks in linking processing conditions with in-service performance under realistic operating environments. The potential of computational intelligence approaches for predicting thermo-mechanical response, damage evolution, and reliability of graded structures is also discussed. Additionally, emerging challenges related to gradient characterization, standardization, technology qualification and scalability, and large-scale deployment are critically discussed, highlighting key directions for future research and technological development. Overall, FGMs and advanced manufacturing show strong potential to improve FPV durability, fatigue resistance, and corrosion performance. Full article

Interfacial bond failure is a common form of distress in rigid–flexible composite pavements, especially in tunnel environments with harsh service conditions. Epoxy-emulsified asphalt (EEA) is widely used as a high-performance interlayer bond coat, but its dynamic damage evolution under coupled thermomechanical loading remains insufficiently characterised. In this work, 45° static oblique shear tests and stress-controlled dynamic shear fatigue tests were performed on a C40 concrete-EEA-asphalt mixture composite system. Tests covered a temperature range of −10 °C to 45 °C, loading frequencies of 1 to 15 Hz, and three stress levels (0.3, 0.4, 0.5). An optimised geometric tangent method (GTM) was adopted to objectively locate the fatigue failure inflexion point, reducing the empirical bias inherent in traditional stiffness degradation analysis. Test results showed that an EEA application rate of 0.8 kg/m² yielded the best overall interface performance, balancing mechanical interlocking and cohesive strength. At this application rate, the interfacial peak shear strength reached 1.72 MPa, with improved interfacial deformation compatibility and energy dissipation capacity. Fatigue damage followed a distinct three-stage stiffness degradation pattern. High temperatures and low loading frequencies accelerated rheological behaviour of the asphalt phase, shortened the stable damage propagation phase, and promoted premature interlayer slippage. Based on the experimental data, a phenomenological fatigue life prediction model was established, incorporating temperature, loading frequency and stress level. The model supports quantitative assessment of progressive interfacial damage and provides practical reference for structural durability design and life-cycle maintenance of composite tunnel pavements. Full article

Laser powder bed fusion produces geometrically complex metallic components, yet fatigue performance consistently falls below that of wrought counterparts. Surface condition, encompassing as-built roughness, residual stress, porosity, microstructure, and oxide layers, is the dominant factor driving this deficit. This review critically examines surface-driven fatigue mechanisms across Ti-6Al-4V, IN718, AlSi10Mg, and 316L alloys. Post-processing strategies, including mechanical polishing, peening, electrochemical polishing, laser polishing, burnishing, and hybrid approaches, are systematically evaluated. The mechanistic roles of surface roughness as a stress concentrator, near-surface porosity as a crack initiation site, and compressive residual stress as a crack-closure mechanism are discussed. Emerging burnishing techniques, particularly electrical current-assisted burnishing, have demonstrated fatigue life improvements of up to five-fold relative to as-built components. These findings underscore the potential of thermo-mechanical surface modification while emphasizing the need for broader validation across a wider range of alloys and loading conditions. Finally, this review identifies critical research gaps, notably the lack of standardized surface characterization protocols and the limited understanding of fatigue under multiaxial and variable-amplitude loading for surface-treated L-PBF parts, and outlines directions for future work. Full article

Carbon fibre-reinforced polymer (CFRP) composites represent promising lightweight materials for automotive powertrain systems, where increasing demands for weight reduction, energy efficiency, and emission reduction are driving the replacement of conventional metallic components. However, automotive powertrain environments expose CFRP materials to elevated temperatures, cyclic mechanical loading, chemical exposure, and tribological interactions, creating complex degradation conditions that significantly influence long-term durability and reliability. This review systematically analyzes CFRP composites for automotive powertrain applications, focusing on the relationship between operational requirements, material selection, reinforcement architecture, manufacturing technologies, and degradation mechanisms. High-performance thermoplastic systems such as CF/PEEK, CF/PPS, and CF/PEKK are critically compared with conventional thermoset composites. CF/PEEK systems demonstrate superior thermomechanical stability, maintaining significant mechanical performance at temperatures approaching 250 °C and tensile strengths of approximately 1400–1600 MPa, whereas CF/PPS composites provide a more economically efficient compromise between thermal resistance, chemical stability, manufacturability, and recyclability for medium-temperature applications. The review further analyzes dominant degradation mechanisms, including creep deformation, fatigue damage, delamination, fibre–matrix interface degradation, and tribological wear. CFRP degradation is shown to result from the interaction of multiple coupled mechanisms rather than from isolated material failure modes. Tribological wear rates typically range from 10⁻⁶ to 10⁻⁵ mm³/(N·m), while creep–fatigue interactions may reduce component lifetime by up to 40–60% under combined thermomechanical loading. Advanced design strategies, including fibre orientation optimization, laminate architecture tailoring, thickness gradation, and hybrid metal–composite structures, are evaluated together with major manufacturing technologies such as injection moulding, compression moulding, overmoulding, automated fibre placement, and additive manufacturing. The presented review establishes an integrated framework linking material systems, operating conditions, manufacturing processes, and durability requirements for automotive powertrain applications. The analysis demonstrates that no universal CFRP system exists for all powertrain components and that optimal material selection requires balancing thermal stability, fatigue resistance, tribological performance, manufacturability, recyclability, and economic constraints according to the specific operating conditions of each component category. Full article

The groove curvature coefficient plays a critical role in determining the thermo-mechanical performance of angular-contact ball bearings. However, its optimization remains challenging due to strong nonlinear coupling among stress, stiffness, heat generation, and fatigue capacity. To address this issue, this study proposes a hybrid optimization framework integrating a corrected two-dimensional axisymmetric finite element method (2D-AxFEM) model, a deep learning surrogate model, and a genetic algorithm. Firstly, an efficient 2D-AxFEM model calibrated by a bearing dynamic model is developed to accurately predict key performance metrics, including contact stress, stiffness, heat generation, and dynamic load rating, with significantly reduced computational cost compared to the conventional 3D FEM model. Based on the generated data, a multi-layer perceptron deep learning surrogate model is trained to establish a fast nonlinear mapping between groove curvature coefficients and performance indicators. The model achieves high accuracy, with R² values of 0.9745, 0.9414, and 0.9756 at three different rotational speeds, as well as significantly improved computational efficiency. Building upon this, single- and multi-constraint optimization problems are solved using a genetic algorithm. The results reveal clear trade-offs among stiffness, heat generation, and load capacity. Under stiffness constraints, optimal solutions consistently converge to the constraint boundary, indicating its dominant role in thermal optimization. Under multiple constraints, the framework effectively identifies feasible design regions, enabling reduced heat generation while maintaining acceptable stress and load capacity. Overall, the proposed framework enables efficient exploration of multi-physics design spaces and provides a scalable solution for high-speed bearing optimization. Full article

Friction stir welding (FSW) is an effective solid-state joining technique for magnesium alloys such as AZ31, owing to its ability to minimize conventional welding defects. Nevertheless, the process generates significant residual stresses that can impair the fatigue performance and dimensional stability of welded structures. In this study, a sequentially coupled thermo-mechanical finite element model was employed to characterize the residual stress distribution in FSW AZ31 Mg alloy. The calculated near-surface longitudinal residual stress was assessed against XRD measurements at five locations on the top surface, giving a root mean square error of about 10.34 MPa. The results revealed an M-shaped longitudinal residual stress profile with marked asymmetry between the advancing and retreating sides, associated with non-uniform heat input and the resulting asymmetric temperature history. Among the three stress components, the longitudinal residual stress was the largest, followed by the transverse component, while the normal stress was the smallest. The thermo-mechanically affected zone and the crown zone exhibited higher residual stresses compared to the heat-affected zone. In addition, the influences of welding speed and tool rotational speed on residual stress evolution were systematically evaluated. The longitudinal residual stress increased with welding speed up to 350 mm/min and subsequently decreased, while a peak value was observed at 1200 rpm. These numerical results provide useful guidance, within the studied parameter range, for welding-parameter selection and residual-stress control in magnesium alloy joints. Full article

Autonomous driving sensor fusion housings (SFHs) integrate LiDAR, radar, camera, and computing modules within a shared mechanical and thermal enclosure. This review examines how coefficient of thermal expansion (CTE) mismatch among housing polymers, aluminum heat spreaders, substrates, and solder joints can contribute to interfacial delamination, solder joint fatigue, optical misalignment, and Thermomechanical Coupling Interference (TMCI). Using a structured narrative review of 99 publications and authoritative standards from primarily 2009 to 2026, the article organizes the evidence into a 4 × 4 taxonomy linking four failure mechanisms with experimental, computational, AI/ML, and qualification-oriented approaches. The review explicitly distinguishes direct literature evidence, transferred package-level evidence, model-based extrapolation, and author-derived conceptual estimates. Accordingly, TMCI temperature increments, sensor spacing values, optical drift estimates, and lifetime projections are discussed only as case-specific screening-level hypotheses unless directly validated in the cited literature. Five research gaps are identified: standardized multi-sensor TMCI validation, aging-corrected material and solder fatigue databases, long-term qualification of thermally conductive nanocomposites, SFH-specific validation of physics-informed digital twins, and integrated multi-failure testing. The contribution of this article is therefore primarily structural and agenda setting: it clarifies what is supported by direct evidence, what is transferred from adjacent domains, and what remains to be validated before robust SFH-level reliability guidance can be established. Full article

Unbonded flexible pipes are key components of deepwater high-temperature oil and gas transportation systems, and their bending performance directly affects in-place response and fatigue assessment. Interlayer contact and sliding of tensile armor layers govern bending hysteresis; under high-temperature service, incompatible thermal expansion of metallic and polymer layers changes contact pressure and the associated slip conditions. This study develops a thermo-mechanical bending hysteresis model in which thermally induced interlayer contact pressure links the radial temperature field to the bending response. A steady-state multilayer-cylinder heat-transfer model and a thermoelastic compatibility formulation are used to determine temperature distributions and interlayer contact pressures. The contact-pressure variation is then introduced into the tensile-armor slip criterion and the incremental moment-curvature relationship, covering non-slip, partial-slip, and full-slip stages. A sequentially coupled finite element model of a 2.5-inch unbonded flexible pipe is established for validation. The numerical model predicts hysteresis loop area and unloading/reverse-loading stiffness with relative deviations of 6.02% and 5.09% from the finite element results, respectively. Increasing internal temperature increases contact pressure and critical slip curvature, prolongs partial slip, and substantially increases hysteretic energy dissipation. The model provides a basis for high-temperature bending stiffness determination and fatigue-oriented analysis of unbonded flexible pipes. Full article

In internal combustion engines, pistons are subjected to coupled thermal and mechanical loading, which can induce temperature gradients, deformation and local stress concentration. In this study, a finite element thermomechanical model of a diesel engine piston with a MgZrO₃/YSZ double-ceramic-layer thermal barrier coating was established to evaluate the effects of the outer-layer material and ceramic-layer thickness distribution. Perovskite ceramics, including MgZrO₃, SrHfO₃, SrZrO₃ and BaTiO₃, were first compared as outer ceramic layers. The MgZrO₃/YSZ configuration showed the most evident thermal barrier response among the investigated materials. Under a constant total ceramic thickness of 0.30 mm, increasing the MgZrO₃ outer layer from 0.10 mm to 0.20 mm increased the coating surface temperature while slightly reducing the maximum substrate temperature, coupled deformation and substrate fatigue rissk. The higher-stress regions of the coating system were mainly located near layer interfaces, whereas the high-stress region of the metallic substrate was concentrated near the pin boss and pin hole transition. The results indicate that outer-layer thickness optimization can improve substrate protection to a limited extent, but the associated increase in ceramic-layer stress should also be considered. Full article

To investigate the effect of print orientation (0°, 45°, and 90°) and artificial aging on flexural strength and fatigue resistance of 3D-printed denture bases compared to CAD/CAM milled controls, we fabricated 320 maxillary complete dentures, divided into 8 groups based on the fabrication method: horizontal, oblique, and vertical printing, alongside milled controls. Half of the specimens in each group were pre-conditioned via thermocycling and 240,000 cycles of chewing simulation. All specimens underwent static flexural strength testing and cyclic fatigue testing, followed by SEM fractography. The CAD/CAM milled bases demonstrated the highest mechanical durability, with non-aged specimens peaking at 149.43 ± 5.35 MPa. The horizontally 3D-printed non-aged specimens yielded the highest flexural strength (101.14 ± 4.80 MPa), while vertically printed aged specimens recorded the lowest (70.35 ± 8.18 MPa). Artificial aging degraded flexural strength uniformly across all orientations. Conversely, cyclic loading disproportionately devastated the older people’s vertical group, resulting in a 70% fracture rate. Fractography corroborated these findings, revealing severe interlaminar delamination in vertical builds, contrasting with cohesive, trans-layer fractures in horizontal prints. In conclusion, Horizontal orientation provided improved structural durability; however, CAD/CAM milled dentures remain superior and are recommended for long-term clinical applications. Full article