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2026 Vol. 47, No. 4 Published: 2026-08-30

	443	Progress in Contact Analysis of Finite-Sized Inhomogeneous Media

		The resolution of forward and inverse contact analysis of finite-sized inhomogeneous media is pivotal to high-throughput characterization of materials. This paper begins with the forward problem, detailing the foundational theory of the symplectic analysis, the strategy for determining contact areas, and the extended formulations for more complicated situations. Two classes of neural operators for solving the inverse problems in 2D and 3D cases are then introduced. A range of challenges to the research of contact analysis of finite-sized inhomogeneous materials are summarized and discussed in the end.
		2026 Vol. 47 (4): 443-454 [Abstract] ( 2 ) HTML (1 KB) PDF (0 KB) ( 0 )

	455	X-ray and Neutron Characterizations on the Microstructure and Mechanical Properties of Railway Vehicle Components

		As China's rail transit network continues to expand in scale and operational speed, the service safety and structural reliability of key components of trains and tracks shows increasingly high requirements on the accuracy, depth, and non-destructive nature of damage examination technologies. Traditional analytical methods struggle to achieve real-time and dynamic tracking of microstructural features inside materials and components. In contrast, synchrotron radiation X-ray and neutron methods are advanced and powerful characterization tools in modern material detection fields. They have acted a crucial role in assessing internal damage in large metal components due to their unique and outstanding advantages such as high brightness, high resolution, and strong penetration capability. This paper systematically reviews the fundamental principles, classifications, and key characteristics of synchrotron radiation and neutron technique. To be more specific, this paper mainly focuses on their recent studies and applications in modern railway materials and components, particularly in composition and microstructure, residual stress measurement, and in situ monitoring of internal defects and fatigue evolution behaviors. It includes the application progress of microstructure characterization of structural materials, residual stress measurement of the wheels, axles and rails, as well as in situ tracking of internal defects and fatigue properties of lightweight materials, etc. While this paper primarily targets mature materials such as alloy steels, it also briefly surveys novel structural materials including titanium alloys, magnesium alloys, and carbon fiber composites. Furthermore, this paper demonstrates the advantages of in situ three-dimensional imaging in capturing the dynamic evolution of defects and neutron diffraction in characterizing the deep residual stress of large-scale components. Collectively, these findings provide key data support for the research and development of advanced rail transit materials, production process optimization and safety assessment under service conditions. Finally, the study outlines the core and practical development direction of promising future in this field, and serves as a vital reference and scientific basis for the further application of non-destructive characterization technology in the railway field.
		2026 Vol. 47 (4): 455-475 [Abstract] ( 3 ) HTML (1 KB) PDF (0 KB) ( 0 )

	476	In situ Experiment Methods and Recent Progress of Internal Damage Evolution of Structural Materials under Extreme Environments

		In recent years, the service environments of railway, aerospace and nuclear equipment have become increasingly extreme with insufficient safety margin, leading to an increasing risk of failure in critical loading components. Developed countries, such as America and Europe, are actively promoting the fundamental and significant role of nondestructively in situ experimental technology in material internal damage characterization. Among these efforts, the cross-scale or full-field modeling of quantitative defect-life correlation has emerged as a common technical challenge for the long-term safety service of advanced equipment under extreme environment. Therefore, this paper, driven by the urgent demand for internal mechanical full-field measurement of the materials and structures, specially addresses the technical challenges faced in the cross-scale assessment of internal damage evolution typically under ultra-high temperature, ultra-low temperature, strong corrosion, and high impact, etc. To tackle this issue, this paper briefly reviews the recent progress and challenge of extreme mechanical testing devices primarily based on high-resolution X-ray imaging and their typical engineering applications and recent progress, specially highlighting the urgency, challenges, and cutting-edge nature of this direction in the community of solid mechanics and engineering science. The deep understanding and potential scenarios of extreme mechanics can assist the rapid development of advanced structural materials, significantly enhancing the capability of bridging the service performance of key equipment and engineering facility from the viewpoints of multiple fields and scales. Such achievement can promote the design capacity of new materials and structures.
		2026 Vol. 47 (4): 476-487 [Abstract] ( 3 ) HTML (1 KB) PDF (0 KB) ( 0 )

	488	Opportunities and Challenges of Atomic Force Microscopy in High-Throughput Mechanical Characterization

		High-throughput atomic force microscopy (HT-AFM) aims to address the challenges of low throughput in traditional AFM, which struggles to characterize material heterogeneity and dynamic processes. This perspective reviews recent technical advances involving high-speed scanning hardware, innovative imaging modes, and artificial intelligence algorithms, and analyzes the challenges in balancing speed, accuracy, and resolution, processing vast amounts of data, and developing functionalized probes. The future trend towards intelligent and multi-modal integration is also discussed, highlighting the potential evolution of this methodology from an observational tool into an analytical engine.
		2026 Vol. 47 (4): 488-501 [Abstract] ( 4 ) HTML (1 KB) PDF (0 KB) ( 0 )

	502	Microscopic high-throughput mechanical characterization technology: Status and Perspective

		Microscopic high-throughput mechanical characterization technology serves as a pivotal approach for revealing the structure–property relationship of materials. This article systematically reviews the fundamentals, recent advances, and future trends in microscopic high-throughput mechanical characterization methods, with a focus on scanning probe microscopy and nanoindentation. The imaging size, scanning speed, and information dimensionality of scanning probe microscopy can be significantly enhanced through the development of parallel probe arrays, high-speed scanning technique, and multi-mode integrated systems. For nanoindentation, the development of high-speed mapping has enabled efficient acquisition and quantitative analysis of various mechanical properties, including hardness, elastic modulus, and fracture toughness. Furthermore, this article focuses on the vital role of data-driven approaches such as machine learning in empowering the aforementioned technologies, including efficient processing of massive data, enhancement of low-quality images, and optimization of experimental processes, significantly improving the characterization efficiency and accuracy. Finally, this article looks forward to the prospects of microscopic high-throughput mechanical characterization technology towards higher throughput and advanced intelligence.
		2026 Vol. 47 (4): 502-521 [Abstract] ( 4 ) HTML (1 KB) PDF (0 KB) ( 0 )

	522	Review on Fatigue Degradation Mechanism and Mechanical Property Optimization of Solid-State Electrolytes

		Solid-state lithium batteries are widely regarded as a key technology for achieving both high energy density and enhanced safety in next-generation energy storage systems. However, the structural stability of solid electrolytes remains a fundamental bottleneck limiting their long-term cycling performance. In this Review, we systematically revisit the failure mechanisms of solid electrolytes from a mechanical fatigue perspective. The paper summarizes the origins of the internal and external forces experienced during battery operation, including electrode volume changes, electrochemically induced stress, current-density inhomogeneity, as well as stack pressure and structural constraints. Collectively, these factors constitute a cyclic loading environment intrinsically characterized by low-cycle fatigue driven by the coupling of internal and external mechanical forces. Distinct from conventional analyses based solely on static strength criteria or isolated dendrite/crack mechanisms, we propose that the failure of solid electrolytes can be more comprehensively understood as a quasi-brittle fatigue process. In this framework, local current-density and stress concentrations, often triggered by intrinsic material defects and interfacial voids, act as initiation sites. Subsequent degradation is accelerated through the mutually reinforcing interaction between crack propagation and lithium dendrite growth. By comparatively analyzing soft and stiff material systems with different mechanical response characteristics, we demonstrate that low-modulus electrolytes tend to exhibit dendrite-dominated failure initiation pathways, whereas high-modulus electrolytes are more prone to crack-dominated fatigue damage. Despite these distinct initiation mechanisms, both systems ultimately converge toward coupled crack–dendrite penetration and catastrophic failure under cyclic mechanical loading. From the perspective of cyclic mechanical loading, we establish a unified framework for understanding the long-term degradation of solid electrolytes. Based on this framework, we further summarize and critically evaluate existing mechanical optimization strategies targeting material defects, interfacial contact stability, and the evolution of cracks and dendrites. Finally, we outline future research directions for solid electrolytes, emphasizing a paradigm shift from a solely high-modulus design philosophy toward “stiff–compliant” architectures that synergistically balance mechanical rigidity and stress accommodation. We advocate for the development of fatigue-lifetime-oriented evaluation metrics and multi-scale predictive models tailored to realistic solid-state battery operating conditions, thereby enabling a transition from empirical parameter optimization to fatigue-informed, life-predictive design spanning from material properties to battery lifetime.
		2026 Vol. 47 (4): 522-538 [Abstract] ( 5 ) HTML (1 KB) PDF (0 KB) ( 0 )

	539	Sliding frictional contact of a piezoelectric half-plane considering size effects

		Abstract With the rapid development of micro/nano electromechanical systems and piezoelectric micro-devices, the size of the devices is continuously evolving towards miniaturization. Under microscale conditions, piezoelectric materials exhibit pronounced size-dependent effects that cannot be accurately characterized by the classical piezoelectricity theory, and these effects have gradually attracted widespread attention in recent years. Based on the couple stress theory, this paper investigates the two-dimensional sliding frictional contact between a rigid insulating or conducting flat punch and a transversely isotropic piezoelectric half-plane. The theory incorporates a characteristic length parameter into the constitutive equations to account for size-dependent effects arising from material microstructure, thereby overcoming the limitations of classical piezoelectric elasticity theory in describing microscale behaviors. The surface electric potential of the conducting punch is assumed to be constant. Coulomb’s friction law is applied over the entire contact region with a constant friction coefficient. Using Fourier integral transforms, the sliding frictional contact problem is reduced to a system of Cauchy singular integral equations. The governing equations are transformed into algebraic equations through a numerical discretization method and then solved iteratively. The influences of the size parameter, friction coefficient, and total electric charge on the in-plane electric displacement, surface electric displacement, surface normal contact stress, and in-plane stress are discussed. It is found that the electroelastic fields predicted by the couple stress theory differ significantly from those obtained from the classical theory. This study provides an important theoretical foundation for the design optimization and reliability analysis of micro/nano electromechanical systems, piezoelectric sensors and actuators, and other piezoelectric devices. By taking into account the size-dependent effects caused by material microstructures, the proposed model can more accurately describe the electromechanical coupling behavior and contact response of piezoelectric materials at the microscale. This is of great significance for improving the operational stability, structural reliability, and service life of micro-devices.
		2026 Vol. 47 (4): 539-553 [Abstract] ( 4 ) HTML (1 KB) PDF (0 KB) ( 0 )

	554	SH waves in a bi-directional functionally graded infinite plate
		Huiming Wang
		Wave propagations of the shear horizontal (SH) wave in a bi-directional functionally graded (BDFG) infinite plate are investigated. The frequency equation is obtained for a BDFG infinite plate with traction free plate faces and the dispersion curves are presented. Numerical results shows that the gradient index has significant effect on the dispersion curves for low branches, while has little effect on those for high branches. When the material is uniform in the x-direction (the in-plane wave propagation direction) but changes exponentially in the z-direction (thickness direction), the dispersion characteristics of SH waves in functionally graded plates are similar to those in uniform plates. As for the gradient index in the z-direction takes different values, there always exists a branch of the dispersion curve where both the phase velocity and group velocity are equal to the shear wave velocity. When the material changes exponentially in the x direction, there is no dispersion curve branch where the phase velocity and group velocity are equal to the shear wave velocity. For each given angular frequency, it always corresponds to a complex wave number, indicating that SH waves will exhibit certain attenuation characteristics when propagating in the x-direction. This investigation has positive significance for parameter inversion of functionally graded materials by using SH waves.
		2026 Vol. 47 (4): 554-561 [Abstract] ( 6 ) HTML (1 KB) PDF (0 KB) ( 0 )

	562	Inverse Problem of Functionally Graded Materials Based on Physics-Informed Neural Networks

		Functionally graded materials (FGMs) are promising for advanced structures due to their excellent mechanical properties, but determining the spatial distribution of their material parameters remains challenging. This paper proposes a physics-informed neural network (PINN) framework to solve this inverse problem. The framework consists of two subnetworks: the strain network used to smooth the noisy strain data, and the elasticity network designed to learn physical information from equilibrium equation. The total loss function consists of data loss, PDE loss, and regularization loss, and the spatial distribution of material parameters is obtained by minimizing the total loss. To calibrate the predicted Young’s modulus, a Saint-Venant principle-based method is proposed. Compared with existing methods that require known boundary stresses, this method only requires experimentally measured loading forces. Numerical results show that the proposed framework achieves accurate identification of FGM material parameters even under high levels of noise. This study provides an effective approach for the inverse design and non-destructive evaluation of FGMs.
		2026 Vol. 47 (4): 562-574 [Abstract] ( 8 ) HTML (1 KB) PDF (0 KB) ( 0 )

	575	Efficient Measurement of Interlaminar Tensile Strength for Ceramic Matrix Composites

		The interlaminar tensile strength (ILTS) of ceramic matrix composites (CMCs) is a key factor governing their reliability in demanding aerospace applications. Currently, the measurement of ILTS mainly follows the ASTM D6415 standard. However, the modulus ratio required for the calculation in this standard must be obtained through additional experiments, which leads to increased material consumption and testing time. To address this specific issue, this paper proposes a highly efficient testing method based on the four-point bending test and digital image correlation (DIC) technology. First, this paper establishes the strain field of the curved beam during the linear elastic deformation stage using DIC technology. Second, based on the anisotropic curved beam theory, the mapping relationship between the modulus ratio and the strain distribution of the curved beam under four-point bending loads is constructed. Subsequently, the Newton-Raphson method accurately calculates the material modulus ratio to determine the ILTS, with its effectiveness verified through experiments. Simultaneously, Acoustic Emission (AE) is also utilized for real-time monitoring. The acoustic signals are time-aligned with the load-displacement curves and DIC images to accurately capture the material failure process. The experimental results demonstrate that the proposed method can effectively measure the ILTS of CMCs and reveal the interlaminar delamination failure process. Moreover, it is found that increasing the inner fillet radius can alleviate the stress concentration effect, thereby enhancing the overall strength of the curved beam. Conversely, the ILTS decreases as the inner fillet radius increases. This is attributed to the considerably weaker compaction effect of the large fillet. The experimental results indicate that the proposed method can effectively measure the ILTS of CMCs. The AE energy evolution and DIC images reveal that the dominant failure mode of the CMCs curved beam is interlaminar tensile failure. This research offers a highly efficient experimental method for measuring the ILTS of CMCs.
		2026 Vol. 47 (4): 575-585 [Abstract] ( 5 ) HTML (1 KB) PDF (0 KB) ( 0 )

	586	A rapid detection method for surface defects in T-shaped welds based on torsional-like guided waves

		T-type welds serve as critical load-bearing components in large-scale engineering structures such as bridges, ships, and offshore platforms. The structural integrity of these welds directly influences the safety and service life of the entire facility, necessitating the development of efficient and reliable nondestructive testing (NDT) methods. Conventional techniques, including bulk wave ultrasound, eddy current, and magnetic flux leakage, rely on point-by-point scanning and prove inefficient for inspecting weld lines extending tens of meters. This limitation underscores the need for rapid, long-distance inspection approaches. In this work, we propose a rapid inspection method for T-type welds based on feature-guided waves. Through semi-analytical finite element analysis, we discovered a torsional-like guided wave mode that exhibits two distinctive characteristics: its energy remains highly confined within the weld region, and it demonstrates nearly non-dispersive behavior above 200 kHz. These properties make it particularly suitable for long-range defect detection. Based on the displacement distribution of this mode, we designed an excitation scheme using thickness-shear piezoelectric patch arrays positioned symmetrically on both weld sides. Three-dimensional finite element simulations confirmed that the torsional-like wave can be efficiently generated and propagates stably along the weld with well-confined energy. Subsequent simulations revealed that this wave mode is sensitive to surface transverse cracks, with the reflected wave amplitude increasing monotonically with crack depth—a feature that enables defect quantification. Experimental validation on a steel T-type weld specimen successfully reproduced the torsional-like wave, and the measured wave velocity showed excellent agreement with theoretical predictions. Raw experimental signals, however, contained defect echoes masked by background noise and multi-mode interference. To address this challenge, we implemented a matched filtering algorithm based on cross-correlation analysis, which successfully extracted weak defect reflections and accurately located the crack position. This study systematically demonstrates the feasibility of employing torsional-like guided waves for rapid defect detection in T-type welds. By enabling a single excitation to scan a long weld section, the proposed method transforms inspection efficiency from point-wise to linear scanning, offering a promising solution for high-throughput NDT of welded structures in practical engineering applications.
		2026 Vol. 47 (4): 586-598 [Abstract] ( 3 ) HTML (1 KB) PDF (0 KB) ( 0 )

	599	Three-Dimensional Discrete Dislocation Dynamics Simulation of Synergistic Deformation Mechanisms in Martensite-Ferrite Dual-Phase Steels

		Martensite-ferrite dual-phase (DP) steel is widely utilized in industry owing to its excellent combination of mechanical properties; however, its microscopic deformation mechanisms remain incompletely understood. To elucidate these mechanisms, this study employs three-dimensional discrete dislocation dynamics (3D-DDD) simulations based on a generalized misorientation-dependent dislocation–grain boundary interaction model. By systematically varying dislocation densities, grain sizes, and interface characteristics, we simulated the mechanical responses and microstructural deformation behaviors of single-phase martensite, single-phase ferrite, and martensite–ferrite dual-phase structures under uniaxial tensile loading. The results show that the elongated grain structure in martensite significantly impedes dislocation motion, resulting in a lower plastic strain accumulation rate and strongly suppressed transgranular dislocation activity. In contrast, ferrite exhibits frequent transgranular dislocation glide and pronounced plastic relaxation. The martensite–ferrite dual-phase structure demonstrates a remarkable synergistic strengthening effect, which is further enhanced by the accumulation of geometrically necessary dislocations (GNDs) at the martensite–ferrite interfaces. This study clarifies the synergistic deformation mechanisms in martensite–ferrite DP steel at the microscale and provides an important theoretical basis for the microstructure-based design of dual-phase steels.
		2026 Vol. 47 (4): 599-612 [Abstract] ( 5 ) HTML (1 KB) PDF (0 KB) ( 0 )

	613	Influence of cementite lamellar continuity on tensile deformation mechanisms of pearlite in S38C axle steel

		To investigate the influence of cementite lamellar continuity on the deformation behavior of pearlite, four atomistic models of pearlite with varying lamellar continuity are constructed based on the experimentally observed cementite lamellae in S38C axle steel. Uniaxial tensile deformation of these models is simulated using molecular dynamics to systematically analyze the influence of lamellar continuity on microstructural evolution and plastic deformation mechanisms. The simulation results indicate that differences in lamellar continuity do not alter the dislocation nucleation mechanism dominated by ferrite-cementite interfaces in pearlite. In continuously distributed cementite lamellae, dislocations primarily nucleate at interfacial misfit dislocations and propagate via slip transfer across phase boundaries. In contrast, for discontinuously distributed lamellae, dislocation nucleation preferentially occurs near high-energy atomic planes. Moreover, as the spacing between discontinuous regions increases, the evolution of dislocation density undergoes significant changes, manifested by a marked reduction in interfacial slip transfer accompanied by local cementite decomposition. Quantitative analysis of the mean flow stress reveals a nonlinear relationship between cementite lamellar continuity and the hardening effect in pearlite, with a moderate reduction in lamellar continuity leading to a significant improvement in hardening response. This work elucidates the fundamental mechanisms through which the characteristics of cementite lamellae govern the plastic deformation and hardening of pearlite at the atomic level, thereby establishing a framework for the design and optimization of such materials.
		2026 Vol. 47 (4): 613-626 [Abstract] ( 4 ) HTML (1 KB) PDF (0 KB) ( 0 )

	627	Creep-Fatigue Interaction Failure Assessment of Combustor Liners under High-Temperature Conditions

		To address the creep-fatigue interaction failure of combustor liners in aero-engines subjected to complex thermo-mechanically coupled loads during high-temperature service, a life assessment methodology for combustor liners under elevated temperatures is developed. Based on a thermo-mechanically coupled cyclic viscoelastic–plastic constitutive model, a creep-fatigue interaction damage model is further introduced. Together, these models provide a unified description of the mechanical response and damage evolution of the material throughout the entire heating-holding-cooling cycle. GH5188 superalloy is selected as the target material. A series of experiments is conducted, including high-temperature tensile tests, low-cycle fatigue tests, and high-temperature creep tests. These experiments are used to identify the material parameters required for the proposed model, as well as to investigate the deformation behavior and creep characteristics of the alloy under cyclic thermo-mechanical loading. The experimental results indicate that the ratcheting effect of the alloy is negligible under the loading conditions considered in this study. Based on the calibrated material parameters, thermo-mechanically coupled finite element simulations of the combustor liner are performed using a commercial software platform. The simulations are employed to analyze the stress-strain response, damage distribution, and life evolution in critical regions of the liner, particularly near mixing holes where stress concentration occurs. The numerical results reveal that, with increasing loading cycles, the damage evolution of the combustor liner gradually transitions from fatigue-dominated to creep-dominated behavior. The proposed methodology provides a more comprehensive description of the coupled mechanical response and damage evolution of combustor liners under high-temperature service conditions. It offers an effective theoretical framework and analytical tool for life prediction and engineering design of high-temperature structural components, with strong potential for practical application in aero-engine structural integrity assessment.
		2026 Vol. 47 (4): 627-644 [Abstract] ( 5 ) HTML (1 KB) PDF (0 KB) ( 0 )

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