Fatigue life prediction is crucial for the safety of metallic materials and structures. Machine learning (ML) models have demonstrated strong predictive capabilities in this field, but their "black-box" nature limits their reliability, trustworthiness, and application in engineering practice. Explainable Artificial Intelligence (XAI) provides key techniques to open the ML "black box". This paper aims to systematically review the current applications of XAI in the field of metal fatigue life prediction. Addressing the issue that current research applies various interpretation methods without systematic categorization, this paper proposes classifying existing methods into two main categories: "post-hoc explanations" and "interpretable by-design". This paper outlines the key techniques of these two categories and their specific application examples in fatigue life prediction, discusses the limitations of model interpretation methods and current technical challenges, and prospects for opportunities and challenges in subsequent research.

Compared to traditional alloys, high-entropy alloys exhibit significant atomic-scale lattice distortion, which endows them with excellent mechanical, chemical, and biological properties, granting them broad application prospects in engineering and biomedical fields. This article briefly reviews recent research progress in the experimental characterization, multi-scale simulations, and mechanical modeling of the lattice distortion effects in high-entropy alloys. Quantifying lattice distortion is a key challenge in the field, providing essential atomic-scale information for multi-scale simulations and mechanical modeling. Through hierarchical multi-scale simulation methods, which integrate small-scale simulations such as molecular dynamics and discrete dislocation dynamics, microstructural parameters can be extracted to inform macroscopic crystal plasticity models, thereby revealing the influence mechanisms of lattice distortion on mechanical behavior. Furthermore, by accounting for atomic size mismatch and shear modulus mismatch, corresponding mechanical models for lattice distortion strengthening have been developed.

The service life of turbine blades is significantly impacted by fatigue crack propagation. The operational environment—characterized by frequent start-stop cycles and exposure to high temperatures and pressures—determines that residual stress is a pivotal factor influencing crack growth. Aiming at the problem of fatigue crack propagation prone to occur in the "hot spot" regions of turbine blades during high-temperature gas turbine operation, a finite element prediction method for fracture life considering the residual stress-driven mechanism is established. This method is based on sequential thermo-mechanical coupled finite element analysis to simulate the evolution process of residual stress induced by high-temperature creep and plastic deformation in turbine blades under Thermo-Mechanical Fatigue (TMF) cycles. Leveraging FRANC3D, an initial crack was introduced into the high-temperature residual stress concentration zone at the blade trailing edge. Combined with the residual stress field, crack propagation paths and life calculations were performed. The study found that significant residual tensile stresses exist in the trailing edge and platform edge regions, serving as the dominant factors for crack initiation and propagation. Among these, the crack propagation life in the trailing edge "hot spot" region is the shortest, approximately 29,000 cycles. Analysis indicates that a smaller width-depth ratio of the initial crack leads to shorter crack propagation life, and the crack propagation trajectory aligns with the direction of the first principal stress. The simulation framework constructed in this paper exhibits good engineering adaptability and can provide solid for foundation fatigue life prediction and optimal design of high-temperature turbine blades.

Method of fundamental solutions is a strong form collocation-type meshfree method, which satisfies governing equation, and its approximated function is the linear combination of fundamental solutions with higher order smoothness. The method has been applied in many science computation and engineering fields, for its easier discretization, exponential convergence and extremely high accuracy. Since the fundamental solution only satisfies the homogeneous differential equation and has singularity on the source nodes, the particular solutions and the fictitious boundaries have to been considered. In this paper, the basic theory and improved methods are introduced firstly. Secondly, the methods for solving particular solutions in the non-homogeneous equations and setting of the fictitious boundaries are given and discussed, including their advantages and disadvantages. Finally, the development of method of fundamental solutions are summarized in order to promote further applications for complex problems in the future.

It is well known that by introducing the physical neutral surface the stretching-bending coupling of the functionally graded material (FGM) plates can be eliminated and the solution of the problem can be simplified. However, the existing physical neutral surface was derived under the assumption of constant Poisson's ratio (ACPR), which ignores the change of the Poisson's ratio in the direction of the plate thickness. In this paper, by abandoning the ACPR, a generalized neutral physical surface of FGM Kirchhoff plate with the material properties varying non-uniformly in the plate thickness is derived and the analytical expressions of related three position parameters are presented. Thus, the strains and equivalent moments of the plate are expressed by the curvatures of the elastic surface, and the stretching-bending coupling between the deflection and the in-plane displacements is eliminated. Furthermore, the equivalent bending stiffness of the static bending of the thin plate is derived, and the influence of ACPR on the accuracy of prediction for the bending deformation of the FGM plate is quantitatively analyzed through the numerical results. Taking a FGM plate with ceramic/metal constituents as an example, if the constant Poisson's ratio is selected as the mean value of the component materials, the maximum relative error between the equivalent bending stiffness derived under ACPR and that derived by abandoning the assumption will be greater than 5%. The present generalized physical neutral surface with three position parameters which is more accurate than those in the literature will be meaningful and helpful to the analysis of static and dynamic responses of FGM Kirchhoff plates.

This study established a mesoscopic model of fiber-matrix interface with three phases based on the phase field method to investigate the crack propagation and damage failure mechanism of steel fiber reinforced ultra-high performance concrete (SF-UHPC) under transverse tensile load. A finite-width interface layer was introduced to simulate the initiation, deflection and propagation of cracks in the interface region. The failure modes of SF-UHPC, steel fiber reinforced normal concrete (SF-NC) and basalt fiber reinforced ultra-high performance concrete (BF-UHPC) under three conditions, namely, with initial matrix defects, with initial interface defects and without initial defects, were compared and analyzed. The results show that the method adopted in this paper can realize the numerical simulation of the complex damage evolution mechanism of the matrix-interface of fiber-reinforced cement-based materials. SF-UHPC shows a failure mechanism dominated by interface-controlled crack propagation, while SF-NC is more characterized by brittle matrix fracture, and BF-UHPC exhibits a multi-stage feature of fiber fracture-interface weakening-matrix fracture. SF-UHPC shows the best crack resistance and ductility in all three conditions. Even without initial defects, cracks in SF-UHPC still initiate from the interface, which is close to the simulation results of interface cracks. The peak bearing capacity and fracture displacement are the highest, with the peak load increased by 210.3% and 46.3%, respectively, compared with SF-NC and BF-UHPC, and the ductility increased by 113.0% and 8.89%, respectively.

Cable-buoy systems serve as critical components in ocean engineering, where their dynamic response under complex flow conditions is directly linked to structural safety and functionality. The fluid drag force is a key factor influencing their dynamic behavior and is commonly modeled using the Morison equation, which can be formulated in either an absolute or a relative velocity framework. The absolute velocity model captures fluid-structure interaction more comprehensively but introduces mathematical complexity that challenges nonlinear vibration analysis. In contrast, the relative velocity model is widely adopted due to its simplicity and computational efficiency, though its approximation errors warrant further investigation. This study aims to systematically compare these two drag force models in the context of nonlinear dynamic response analysis of cable-buoy systems. Based on elastic cable theory, nonlinear governing equations are derived for both models, and the intrinsic modal characteristics of the system are examined through linear vibration analysis, with particular attention to the Veering phenomenon and the associated strong modal coupling. Direct numerical integration is then performed to compare system responses under different reference frames. The results indicate that the coupling term between current velocity and structural velocity in the absolute velocity model enhances system damping, leading to smaller predicted response amplitudes compared with the relative velocity model. In the strong coupling regions where modal Veering occurs, discrepancies between the two models are significantly amplified, but the overall impact on global dynamic behavior remains limited. Therefore, the study reveals that under conditions of low current velocity, dominant structural damping, or engineering applications with moderate accuracy requirements, the relative velocity model, despite its approximation errors, serves as an efficient and practically valuable simplification. This conclusion provides theoretical guidance for the rational selection of drag force models in the engineering design of cable-buoy systems.

Moderately thick plates are widely used in engineering structures, and assessing their ultimate load-bearing capacity is critical for ensuring structural safety. Based on the first order shear deformation theory, this paper presents a smoothed finite element method for upper-bound limit analysis of moderately thick plates governed by the von Mises yield criterion. The edge-based smoothing domains are further formed based on the triangular elements and all strains are averaged independently within each smoothing domain. To effectively avoid shear locking, the mixed interpolation of tensorial components technique (MITC) is introduced, where the shear strain components are independently interpolated at the midpoints of the triangular element edges. Once the plastic dissipation power is determined through integration over both the middle plane and the thickness of the plate, the upper bound limit analysis can be expressed as a dissipation power minimization problem with a series of equality constraints, which is further transformed into a standard second-order cone programming problem and efficiently solved by the MOSEK solver. Some numerical examples demonstrate that the present method can reliably provide upper bound limit load multipliers for moderately thick plates, and no shear locking phenomenon is observed.

Deoxyribonucleic acid (DNA), as the fundamental genetic material of life, possesses diverse mechanical characteristics endowed from its unique chemical and physical properties. These properties play a pivotal role in regulating gene expression, viral infection mechanisms, disease diagnostics, and intelligent nanodevices. A profound understanding of the mechanical properties and behaviors of DNA-like material—spanning from the molecular scale to the macroscopic device level—provides a foundation for unveiling the physical mechanisms underlying biological activities, advancing biomedical detection technologies, and enabling the precise design of dynamic nanodevices. This paper systematically reviewed recent research progress on the mechanical properties of DNA-like material and their applications in biomedicine and nanotechnology. First, some significant experimental advances across different-scale DNA systems were introduced, emphasizing how experiments revealed the influence of microstructure and environmental conditions on the mechanical properties and responses of DNA-like material. Second, the developments of theoretical models for the mechanical behavior of DNA-like material were explored, elucidating the mechanisms underlying relevant experimental findings. Finally, the paper identified the challenges in the current DNA-like material mechanics research and its practical implementation, and looked forward to the prospect of achieving breakthroughs through research paradigms such as "digital and intelligent mechanics".

The multiphysics simulation of transmission and transformation equipment often involves complex coupling processes and high-dimensional computations, resulting in high computational costs and slow response, which hinder real-time prediction and online monitoring. To address this issue, this study proposes a lightweight reduced-order modeling approach for efficient prediction of transmission and transformation equipment. First, sparse multiphysical field data of the equipment under various operating conditions are obtained through full-scale simulations. Then, the Proper Orthogonal Decomposition (POD) method is employed to extract the dominant feature modes of the system, enabling reduced-order reconstruction of the full-order model. On this basis, machine learning algorithms are integrated to perform nonlinear mapping and reconstruction in the reduced-order feature space, thereby establishing a lightweight reduced-order prediction model. Validation on representative transmission and transformation equipment cases demonstrates that the proposed method can reduce simulation time from several hours or even days to only a few minutes or seconds, achieving an overall computational efficiency improvement by several hundred times while maintaining prediction errors within 5%. The experimental results confirm the superior balance between computational efficiency and prediction accuracy. This research provides a feasible pathway for the lightweight and real-time simulation of multiphysical fields in transmission and transformation equipment, with broad applicability in digital twin construction, operational state assessment, and intelligent maintenance of electrical equipment, offering key algorithmic support for the efficient and safe operation of power systems.

As various microelectronic components increasingly require maintenance-free power supplies, and given the natural presence of vibrational energy in their operational environments, harvesting this vibration energy for powering devices represents a viable alternative to conventional energy sources. At present, the vibration energy harvesting technology mainly focuses on the viscous damping acquisition system, while van der Pol damping has a wide range of applications in electronic engineering, aerodynamics, biology and other fields. However, the works of van der Pol damping vibration energy harvesting system are rarely reported. In this paper, the bursting oscillation phenomenon and harvesting performance of tri-stable energy harvester are studied under van der Pol damping for low frequency external excitation. By using the fast-slow analysis method, the bursting oscillation mechanism of the system is analyzed, and the bifurcation of the limit cycle is observed. Using the numerical method, the bifurcation mechanism of the system at different frequency ratios is verified by transformed phase diagram. According to the time history of the system response, large bursting oscillation and high stable voltage response are found. Finally, the average output voltage of the system under external excitation with different frequency ratios is calculated and compared with the viscous damping system. The results show that the tri-stable energy harvester with van der Pol damping has higher acquisition performance. In addition, the effects of different damping on the output power are compared, and the optimal output power is discussed.

Aiming at the challenge of accurately predicting low-cycle fatigue (LCF) life caused by uneven temperature and stress distributions in hot-end components, this paper proposes a novel multi-parameter-influenced LCF life prediction model. This model innovatively incorporates critical parameters including total strain amplitude, elastic strain ratio, maximum principal stress, and temperature. Firstly, based on the degradation model, LCF life prediction analysis was conducted for a nickel-based superalloy under multiple temperature conditions (RT-650 ℃).Results demonstrate that under single-temperature conditions, compared with the traditional Manson-Coffin model and SWT (Smith-Watson-Topper) model, the proposed model achieves significant accuracy improvement-with only one outlier at 650 ℃ falling between ±1.5 and ±2 scatter bands, while all other data points strictly converge within the ±1.5 scatter band. Secondly, through global parameter optimization algorithm for multi-temperature field data fusion, combined with leave-one-out cross-validation (LOOCV) and generalization capability tests, the model exhibits robust performance with 91.9% of predicted points located within ±2 scatter bands. It also demonstrates excellent extrapolation capability for non-tested temperature conditions and adaptability to various engineering alloy materials. Final engineering validation shows good rationality of the results when applying this model to LCF life assessment of a small gas turbine turbine disk, providing a new theoretical methodology for high-temperature component LCF life evaluation.

A hydraulic conductivity model of cement soil, which consider both cement content and curing time, was proposed to quantitatively estimate the permeability of cement soil. A porosity calculation model for cement soil during the cement hydration process was established by introducing the degree of hydration. A pore structure factor was defined, and a power-law relationship between the soil pore structure factor and the plasticity index of the soil was constructed. By introducing a normalized pore structure factor, a functional relationship between the pore structure factor, cement content, and degree of hydration was established for cement soils. Based on the permeability model derived from pore-pipe flow in porous medium, a semi-theoretical and semi-empirical permeability model for cement soil was finally proposed, considering cement content and curing time. The model requires three basic parameters: the plasticity index of the soil, the initial water content of the cement soil, and the water-to-cement ratio. The model was validated using permeability test results of six different types of cement soil. The results showed that the model can effectively reflect the impact of cement content and curing time on the hydraulic conductivity of cement soil. The research in this paper provided a theoretical basis for the quantitative analysis of the permeability characteristics of cement soil and had merit in theory and engineering application.

For the structure of film cooling holes for aircraft engine turbine blades, the fatigue tests of specimens with film hole structure under different stress ratios were carried out. The fatigue limits under different stress ratios were obtained. The stress ratio-fatigue strength diagram at 107 equal life was drawn, and the data were fitted to obtain the ultimate strength of the film cooling hole structure, and the relationship between fatigue strength and stress ratio was obtained. The relationship was transformed into an equal life relationship of 107 under average-amplitude stress. The equal life curves under different equal life equations were compared and analyzed, and the difference of equal life law of film cooling hole structure was obtained. Comparing equal life data of film cooling hole structure with the 107 equal life curve of the material level, the influence of the hole structure on the equal life law of the nickel-based single crystal alloy was obtained. From the perspective of equal life analysis, the near-field stress around the hole was proposed as the reference value for the life assessment of the film cooling hole structure. To evaluate the fatigue life of film cooling hole structures from the perspective of equal life analysis, the new evaluation method was proposed using the near-field stress around the film cooling hole as the reference value.

This study employed the finite element method with a unit cell model to investigate the quasi-static compressive response of nanofluidic energy absorption systems and the influence of unit cell geometry. The unit cells comprised hydrophobic nanoporous materials, water, and a sealing layer, in three shapes: cylindrical, hemispherical, and frustum-shaped. Simulations show that the unit cell's compression response has three parts and four stages: elastic compression of nanopores without liquid (Stages Ⅰ, Ⅱ), liquid penetration into nanopores (Stage Ⅲ), and elastic compression of nanopores with liquid (Stage Ⅳ). The compression stiffness of Stages Ⅰ~Ⅳ depends on sealing layer deformation, water's bulk modulus, nanopores' critical penetration pressure and surface area, and water's bulk modulus, respectively. Unit cell geometry mainly affects Stage Ⅰ; its influence on compression response decreases significantly after Stage Ⅱ. Compared with the cylindrical unit cell, the hemispherical one has ~1 order of magnitude lower initial stiffness and ~1.6 times higher displacement; the frustum-shaped one has slightly higher initial stiffness than the hemispherical one and ~2.5 times higher displacement than the cylindrical one. This difference comes from spatial constraints of adjacent unit cells, i.e., the cylindrical unit cell has the smallest deformable volume, while the frustum-shaped one has the largest. Additionally, the sealing layer's maximum stress is insensitive to the unit cell geometry, with a difference ≤7%.

The flexible hinge driven by the tape-spring can elastically fold and store strain energy. By releasing the stored strain energy, it can be freely deployed and used for the deploying/folding of the deployable structure of spacecraft. This paper carries out the structural design and simulation analysis for the tape-spring hinge. It is found that the bending center has a certain influence on the peak moment (M_d) and steady-state moment (M^*) of the hinge. Selecting an appropriate bending center can cause a singularity (where the moment becomes zero) in the moment-rotation curve of the tape-spring hinge. Furthermore, a physical model of the hinge was fabricated based on the design. The bending angle of the hinge at equilibrated state was measured through the bending experiment. It was proved that there was indeed a state of zero moment in the tape-spring hinge, which was the state corresponding to the singularity in the moment-rotation curve. Tape-spring hinge could remain stable at the bending angle corresponding to this state, thereby verifying the rationality of the simulation analysis. It also provides design references for engineering applications.

This study presents a novel nonlocal macro-micro-scale consistent phase transition thermodynamic model (NMMP), integrating the nonlocal macro-meso-scale consistent damage framework with the foundational principles of unified phase-field theory. The NMMP model addresses the inherent limitations of conventional phase-field approaches that necessitate dual-field coupling of phase and temperature variables. At the microscale, the material structure at any point is idealized as a hub-shaped bond system within a finite interaction radius, where the phase transition state of each bond is governed by a thermal flux intensity criterion. The critical thermal flux threshold is equivalently calibrated based on the latent heat associated with the phase change. Macroscopically, the topological phase variable at a material point is derived through a weighted average of the bond-level phase transition states. Correspondingly, a thermal conductivity evolution function is formulated to capture the dynamic adaptation of thermophysical properties such as thermal conductivity and heat capacity, contingent on the evolving macroscopic phase state. The NMMP model is implemented within a finite element framework to derive the transient temperature field equations. Further comparison with coupled temperature-phase field simulations under phase transition scenarios demonstrates the model's robustness and fidelity. Notably, the NMMP approach captures the essential thermodynamic features of phase transitions driven solely by temperature field evolution, offering an efficient computational strategy for simulating phase transition phenomena and providing a theoretical basis for the thermal regulation of microstructural design.

Considering both the meso-structure of concrete and the rough morphology of the new-to-old concrete interface, a mesoscale finite element model of new-old concrete beams is established to analyze their damage and failure process. A random aggregate model is employed to generate the meso-structure of concrete, in which aggregates are modeled as linearly elastic, while the mortar and the interfacial transition zone (ITZ) between mortar and aggregate are simulated using the concrete damaged plasticity (CDP) model, and the new-to-old concrete interface is modeled using a combined cohesive-friction model. Compared with experimental results of the flat interface, the relative error of flexural strength is 2.22%, validating the effectiveness of the model. The effects of the rough tooth depth (3 mm, 6 mm, 9 mm, and 12 mm) and number of rough teeth (2, 4, 6, and 8) on the new-to-old concrete interface are analyzed, along with the effect of interfacial friction coefficient. The results indicate that the geometric parameters of the rough teeth have a significant effect on the peak load, post-peak load, and damage evolution process. When the rough tooth depth R increases from zero to 12 mm, the peak load increases by 54.1%, and the post-peak load increases from zero to 3.91 kN. As the number of rough teeth N increases from 2 to 8, the peak load and post-peak load increase by 16.4% and 122.0%, respectively. The friction coefficient f notably impacts the post-peak load but has a limited effect on the peak load and crack propagation paths.

Health monitoring of wind turbine is an important means to ensure safe operation. The traditional contact-based detection techniques have drawbacks such as additional weight and cumbersome installation. Research is carried out on the  displacement measurement method of wind turbine blade and tower based on non-contact optical inspection and DIP (Digital Image Processing). The HSV (Hue Saturation Value) color space method is used to extract the coordinates of the wind turbine blade markers, and the degree of deformation of the wind turbine blades is evaluated based on the calculated angle between adjacent blades. The ORB (Oriented FAST and Rotated BRIEF) feature point detection and knnMatch (k-NearestNeighbor Match) feature matching technology are used to identify the coordinates of the regions of interest on the tower, achieving fast measurement of tower vibration displacement. Additionally, the feasibility and accuracy of the above methods are validated using an angle measuring instrument and DIC (Digital Image Correlation).

The mechanical response of geotechnical granular materials exhibits multi-scale characteristics. The multi-scale simulations coupling the Finite Element Method (FEM) and Discrete Element Method (DEM) can effectively capture the multi-scale responses while maintaining high computational efficiency. A GPU-parallel FEM-DEM coupling code was developed based on the high-performance DEM software MatDEM, with computational parameters and results analyzed in conjunction with granular pore fractal characteristics. Firstly, multi-fractal theory was employed to investigate the spatial distribution characteristics of pores, identifying key fractal indices. Subsequently, the reliability of the FEM-DEM coupling code was verified through single element tests and biaxial compression tests. Finally, the meso-scopic responses of Representative Volume Elements (RVEs) at different locations were investigated based on biaxial compression tests. Results demonstrate that the pore spatial distribution within RVE exhibits multi-fractal characteristics. When the particle quantity exceeds 400, the self-similarity of pore spatial distribution ensures the stability of stress-strain responses output after homogenization of granular assemblies within RVE. The capacity dimension D0 and singularity index α0, which characterize the average information of pore distribution, show linear correlations with RVE volumetric strain. These indices can serve as internal variables reflecting the complexity of granular material spatial characteristics. This study provides an exploration for analyzing the macro-meso mechanical relationships in engineering-scale granular deposits.

A unified free rate-independent elastoplastic model is proposed to simulate fatigue of metals under cyclic loading-unloading. Based on logarithmic objective rate with Euler formulation, new constitutive equations are established to overcome the problems of non-integrability of elastic part and shear oscillation. The smooth stress-strain relationship throughout the entire deformation process can be derived by new constitutive equations. These equations are not subjected to and hence free from the usual extrinsic restriction, including the yield condition as well as the loading-unloading conditions. The new model with simpler formulation can avoid tedious calculations and make it more in line with actual situation. An elastic-to-plastic transition factor, which depends on the yield function, is proposed to characterize the proportion of plastic/elastic part in the process of deformation. The yield condition is a restrictive (coercive) condition which is imposed from outside in a classical formulation. Nevertheless, in the new model, the yield surface becomes an inherent feature. Not only may this feature be of interest from a physical point of view, but it may also be of significance to numerical treatment. The simplest case with no reference to the hardening variables is proposed to simulate stress-strain relationship under cyclic loading-unloading. The plastic deformation and plastic work can be induced at any deformation stage, albeit it may be very small at stress level below the usual yield stress. Thus, high-cycle fatigue can be explained and predicted by this new model. It appears that the phenomenological physical essence of material failure and rupture would be just the loss of stress-bearing capability attendant with fully developed plastic flows. A simple formulation of yield strength is proposed, which is dependent on the accumulation of the plastic work. When the accumulation of the plastic work reachs the threshold with sufficient load cycles the yield strength approaches 0, which means the material loses the ability of resistance to deformation and fatigue failure occurs. The results indicate that the new model can accurately match and predict experimental data, providing new ideas for the design of metal materials.

The dynamic characteristics of axial telescopic wing, which is usually simplified to axially moving cantilever plates, is studied in this paper. As a complex time-varying structure, the axial telescopic cantilever plate has time-varying mass, stiffness and damping. Compared with fixed-length structures, this type of structure is more prone to significant vibration and flutter instability under the action of complex external forces, leading to structural instability and failure, and affecting the working accuracy and service life of the structure. Therefore, it is of vital importance to study the stability issue of the telescopic cantilever plate. This paper studies the stability of the axial telescopic cantilever plate for the first time through two methods. Dynamic characteristics and stability of cantilever deploying laminated composite rectangular plate subjected to aerodynamic force is analyzed. Based on von Karman classical plate theory and Hamilton's principle, the two-degree-of-freedom differential equations of the telescopic cantilever plate are established. The ordinary differential equations of the telescopic cantilever plate are obtained by Galerkin methods. The influence of axially moving acceleration and velocity on frequency and amplitude during the extension and contraction of the plate is studied by numerical method. The results show that the amplitude of the axially moving cantilever deploying plate shows periodic changes in the initial stage of plate deployment. When the length of the plate increases to a certain extent, the periodic oscillation of the system disappears and the structure undergoes divergent instability. The influence of velocity, acceleration and plate thickness on the stability of the axial cantilever deploying plate is studied by the transient eigenvalue method, and the stiffness matrix method is used for comparison and verification. The results achieve good consistency, indicating the effectiveness of these two methods.

In order to realize the non-reciprocal elastic wave propagation in materials or structures, the introduction of geometrically asymmetric microstructures is a simple and effective method. In this paper, random piezoelectric composites with aligned spherical cut inclusion are considered, and the non-reciprocal elastic wave propagation in the materials is studied. Firstly, the Dirac function and its derivative functions in the volume average tensor of the dynamic Green's operator in the spherical cut inclusion are eliminated by integral transformation. Then, the self-consistent equations of the dynamic effective properties of piezoelectric composites are solved numerically using the iterative method. The degradation results are verified by comparing with the experiments. Next, the dynamic effective properties of the composites under two elastic waves of identical form but incident in opposite directions are calculated, taking the frequency of the wave and the shape parameter of the inclusions as variables, respectively. We observe non-reciprocity phenomena in some frequency ranges, and find that the degree of non-reciprocity varies when changing the shape of the inclusions. It indicates that specific wave properties can be realized through reasonable microstructure design in practical engineering applications, providing a new idea for the modulation of elastic waves in piezoelectric composites.

In the precursor impregnation pyrolysis (PIP) process of ceramic matrix composites, the viscosity of the precursor liquid significantly affects the effectiveness and efficiency of its infiltration into the fiber preform. The solute mass fraction influences the viscosity itself in the impregnation solution. To provide a theoretical basis for optimizing the impregnation process, this study establishes an apparent viscosity model for precursor liquids with different solute contents. Firstly, an order parameter describing the solid and liquid phase content is introduced, establishing the interrelationship between shear stress, shear rate, and the order parameter of the precursor liquid. Then, based on Landau phase transition theory and the variational principle of the Lagrangian energy functional, a differential equation for the order parameter is constructed and solved, yielding an approximate analytical expression for apparent viscosity, mass fraction, and shear rate in a subdomain. Furthermore, a first-order approximation of the Bernstein polynomial is employed to extend the model to the entire computational domain, resulting in a viscosity model applicable to precursor liquids with different solute mass fractions. Finally, precursor liquids incorporating two types of additives, powders and binders, are examined. By calculating the effect of different mass fractions of additives on precursor viscosity, the validity of the model is verified, and the influence of solute mass fraction and shear rate on the apparent viscosity of the precursor liquid is analyzed based on the viscosity model.

The presence of holes alters the strain and stress distribution in wood beams during bending, making it challenging to accurately predict the neutral axis position of wood beams with holes and assess the health status of wood structures. Therefore, based on the plane-section assumption and the ideal trapezoidal stress distribution model, this paper proposes a predictive model for calculating the neutral axis position of both defect-free wood beams and wood beams with holes. Additionally, the accuracy of the neutral axis position prediction model is validated through four-point bending tests on wood beams using Digital Image Correlation (DIC) technology. When the load level is at Fmax/3 or 2Fmax/3, there is good agreement between the theoretical predictions and the results of the four-point bending tests. However, when the wood beams with a hole are under the ultimate load, the maximum tensile strain exceeds the elastic limit, which causes the plastic deformation to appear in the tension zone, and leads to deviations between the theoretically predicted neutral axis position and the experimental results. The theoretical calculation model is capable of accurately predicting the position of the neutral axis in defect-free wood beams as well as in wood beams with a hole, which can provide theoretical basis and experimental support for the health monitoring of wooden structures based on the position of the neutral axis.

To address the complexity of analyzing torsional vibration responses in pile groups within orthotropic layered foundations, this study proposes an efficient analytical method. Innovatively incorporating a geometric phase correction Hankel integral transform to address wave interference in circular pile groups, this method combines a generalized transfer matrix approach to establish a three-dimensional coupled pile-soil-pile dynamic model. It derives an explicit frequency-domain solution for the torsional dynamic impedance of pile groups. This method reveals the coupling mechanism between pile spacing and soil anisotropy parameters, establishing simplified design formulas covering typical engineering parameters. Computational efficiency is significantly improved compared to traditional three-dimensional simulations. The results indicate that pile spacing and arrangement significantly alter impedance spectrum characteristics by regulating wave interference effects, while anisotropy parameters and interlayer reflection coupling jointly influence torque distribution patterns. These findings provide theoretical support for pile foundation design in coastal sedimentary strata.

Recycled concrete serves as a critical pathway for resource utilization of waste concrete, effectively mitigating environmental pressures caused by natural aggregate consumption and accumulation of construction solid waste. This study employs the generalized mixture rule theory to develop a predictive model for the influence of coarse aggregate replacement ratios on the elastic modulus, compressive strength, and fracture energy of recycled concrete. The model's reliability is validated through multiple experimental datasets from literature. Building on this foundation, the work integrates phase-field fracture theory to propose a constitutive fracture model for recycled concrete under variable replacement ratios, subsequently applied to numerical simulations of three-point bending beam failure processes. Key findings include: (1) The model accurately predicts mechanical parameters' dependence on replacement ratios, with close alignment between calculated and measured values; (2) The phase-field method achieves high consistency in crack propagation paths and load-CMOD curves with experimental results, validating the model's applicability in engineering structural failure analyses.

This study systematically investigates the influence of the wall slip length (L_s) on the statistical properties and flow structures of turbulent channel flow. The Navier slip boundary condition is applied at the boundary of turbulent channel flow, and direct numerical simulation (DNS) is employed to numerically explore the evolution of turbulence for L_s ranging from 0 (no-slip) to 0.1. The results reveal that as L_s increases, the viscous damping effect at the wall is substantially reduced, resulting in an overall elevation of the mean velocity profile. Within the viscous sublayer, the mean velocity increment exhibits a linear relationship with L_s, satisfying the relation ∆〈U〉^+=Re_τ L_s. In the near-wall region, the turbulence fluctuation intensity demonstrates an enhanced dependence on , with the intensification of Q2 (ejection) events leading to an elevated Reynolds stress peak that shifts closer to the wall. Analysis of wall-attached low-speed streaks indicates that, for a dimensionless wall-normal structure scale l_y^+ < 50, both their number and volume increase significantly with rising L_s. Furthermore, it is found that the effects of the wall slip condition are confined to the near-wall region, while the outer inertia-dominated region continues to follow the scaling laws of no-slip wall turbulence.

To elucidate the complex bonding and fracture mechanisms at the interface between Ultra-High Performance Concrete (UHPC) and Normal Concrete (NC), this study systematically investigates how interfacial roughness and mesoscale structural characteristics influence interface mechanical performance. Four interface treatments (i.e., smooth surface, high-pressure water jetting, sandblasting, and chiseling) were comparatively analyzed through direct tension and shear tests, complemented by quantitative surface roughness characterization using laser scanning. Furthermore, X-ray Computed Tomography (X-CT) facilitated the three-dimensional reconstruction of UHPC-NC mesoscale structures, enabling advanced segmentation of pores, fibers, and other structural phases via deep learning algorithms. Multi-scale finite element modeling based on X-CT data simulated the damage evolution and crack propagation at the interface. Results indicate that chiseling significantly increased interfacial roughness, yielding substantial improvements in direct tensile and shear bond strengths by 123% and 126%, respectively, relative to the smooth surface. X-CT analysis revealed a distinct hydration transition zone at the interface, significantly influencing chemical bonding and exhibiting notably lower porosity compared to the NC matrix. Steel fibers from UHPC penetrated into the NC substrate, creating enhanced mechanical interlocking effects. Numerical simulations demonstrated that interface failure mechanisms are jointly governed by tensile failure within the NC substrate and crack propagation through the interfacial transition zone (ITZ), consistent with experimental observations of mixed-mode fractures. Overall, enhanced interfacial roughness improved bonding strength through both mechanical interlocking and chemical adhesion, while mesoscale structural defects critically influenced crack development pathways. The proposed multi-scale analytical approach provides comprehensive methodological support for optimizing the design and rehabilitation of concrete interfaces in engineering practice.

Split-sleeve cold expansion technology is a critical process for improving the fatigue life of aerospace structural components. However, the influence of its parameter variations on fatigue performance remains insufficiently studied. This paper systematically investigates the sensitivity of initial hole diameter, thickness of split-sleeve, and diameter of the extrusion zone of the mandrel on the fatigue life of 7050-T7451 aluminum alloy through integrated fatigue testing, finite element simulation, and machine learning methods. Based on the S-N curve model of 7050-T7451 aluminum alloy and the critical distance line method, a fatigue life prediction model for cold-expanded holes was established. The model was then used to generate datasets for training an intelligent fatigue life prediction model. Leveraging 400 000 data points obtained from the intelligent model, Sobol global sensitivity analysis was conducted to quantify the independent and interactive contributions of these parameters to fatigue life.Results　indicate that the initial hole diameter has the most significant impact on fatigue life, dominating both independent effects and synergistic interactions, while the influence of Thickness of split-sleeve and mandrel diameter primarily manifests through interactive mechanisms. The study proposes prioritizing tolerance optimization for initial hole diameter while adopting collaborative design strategies for sleeve thickness and diameter of the extrusion zone of the mandrel. This methodology provides an efficient and economical approach for identifying critical process parameters and optimizing designs, demonstrating significant advantages over traditional physical experimentation and finite element analysis.

Interface consistency and error convergence are central issues in concurrent multiscale computational methods, particularly critical for atomistic-to-continuum coupling models. However, existing theoretical studies remain limited and are mostly confined to one-dimensional settings. This work focuses on the multiresolution molecular mechanics (MMM) approach and systematically investigates the impact of various energy sampling schemes on interface consistency and error convergence. Two-dimensional square and triangular lattice models containing both atomistic and coarse-grained regions are constructed under bilinear element interpolation. The results show that interface secondary sampling schemes can significantly improve consistency in the interfacial region, with the scheme incorporating all neighboring layers achieving the best performance. Error analysis reveals that discretization error dominates the total error, and increasing the number of secondary sampling points effectively reduces the sampling error, particularly under tensile loading conditions. Moreover, both lattice types exhibit consistent error convergence behavior, demonstrating high generality of the method to different structures. This study highlights the advantages of energy sampling strategies in improving interface treatment and convergence behavior in MMM, providing theoretical support for the development of high-accuracy multiscale computational mechanics methods.

This paper investigates the nonlinear vibration isolation problem of simply supported beam bridge structures under displacement excitation, employing the Incremental Harmonic Balance Method (IHBM) to derive an approximate analytical solution for the nonlinear vibration response of the beam. The research focuses on a coupled system consisting of a quasi-zero stiffness (QZS) isolator, constructed using a three-spring system, and a simply supported beam bridge. Based on the classical Euler-Bernoulli beam theory, the governing equations of motion under displacement excitation are established and systematically solved using the IHBM, with the entire analytical process thoroughly derived. The study transforms the final solution into a linear matrix equation using generalized coordinates, achieving a procedural and standardized computational process. To validate the reliability of the IHBM approximate analytical results, the study compares the IHBM computational results with numerical solutions obtained using the fourth-order Runge-Kutta method (ODE45). The results demonstrate that the IHBM method exhibits significant advantages in computational stability and result completeness. Additionally, through parametric analysis, the study explores the influence of key isolator parameters on system amplitude, further confirming the effectiveness and engineering practicality of the IHBM in nonlinear vibration isolation research. The research outcomes provide new theoretical foundations and methodological references for the nonlinear vibration isolation analysis of simply supported beam structures, offering important guidance for engineering practice.

In the process of energy storage and power generation in molten salt tanks, the ceramic particle layer at the bottom of the tank plays a critical role in load-bearing and thermal insulation. Under cyclic loading, analyzing the effects of particle compression, flow, and contact stress on the overall settlement of the ceramic particle layer provides an important basis for design. In this study, the Hertz-Mindlin contact model in EDEM software was employed to establish a discrete element particle simulation model for the ceramic particle layer at the bottom of the molten salt tank. Simulations were conducted for the compaction backfill process and full-tank working conditions, and a comparative analysis was performed to investigate the effects of pre-compaction processes and particle size distribution on the compression settlement and maximum equivalent stress of the ceramic particles, as well as the influence of randomness in discrete element analysis results. The results indicate that for a ceramic particle layer height of 1.6 m and a particle size range of 5~20 mm, adopting a segmented compaction backfill process under a 50 000-ton tank load results in a maximum internal particle stress of 18.1~21.8 MPa and an overall settlement of 20.44~29.6 mm. As the particle size increases, the maximum stress decreases, with a maximum stress of 12 MPa observed for particle sizes of 15~20 mm. However, the settlement increases significantly, reaching 184 mm. Therefore, a wide particle size distribution range is beneficial for reducing settlement. Considering these factors comprehensively, the optimal configuration is a particle size range of 5~20 mm with a segmented and repeated pre-compaction process. Accounting for the influence of particle randomness, the maximum stress of the ceramic particle layer is 23.16 MPa, and the maximum settlement is 23.5 mm, meeting the design requirements.

Optimization of the natural frequencies of exponential functionally graded plates is a critical issue in the engineering field, playing a vital role in enhancing the dynamic performance of plate structures. In response to this challenge, this paper presents an innovative optimization approach that synergistically integrates the smoothed finite element method (SFEM) with surrogate models, aiming to address the problem with both high efficiency and precision. Based on the first order shear deformation theory, a SFEM is established for free vibration analyses of functionally graded plates. During the computation of the system stiffness matrix, gradient smoothing operations are applied to bending strains within smoothed domains, effectively improving computational accuracy. To overcome the shear locking phenomenon, different interpolation forms are adopted to treat bending strains and shear strains separately. For natural frequency optimization, a series of sample points are selected, and their corresponding natural frequencies are calculated using the SFEM. Subsequently, a surrogate model is established to map the relationship between the gradient index and the natural frequencies. The golden section method is employed to determine the optimal gradient index that achieves preset natural frequency targets. Numerical examples demonstrate that the surrogate model based on piecewise cubic Hermite interpolation exhibits high computational accuracy. Moreover, the surrogate model-based optimization significantly reduces the number of SFEM frequency calculations required, substantially enhancing optimization efficiency. This approach provides an efficient and practical method for optimizing natural frequencies of exponential functionally graded plates.

This study focuses on the integrated manufacturing process of sensors in unbonded flexible pipes for deep-sea mining engineering, investigating the sensor integration process with compensation reinforcement layers and their mechanical performance. A simulation model for the winding process of the compensation reinforcement layer in flexible pipes was established, systematically analyzing the influence patterns of winding tension and winding angles on sensor integration processes. Additionally, the effects of sensor quantity and winding angles on the tensile performance of integrated compensation reinforcement layers were explored. The results demonstrate that winding tension significantly affects sensor elongation rates, while winding angles predominantly influence stress distribution in the lining layer. The tensile performance of integrated compensation reinforcement layers shows minimal sensitivity to sensor quantity, and variations in winding angles within a specific range exhibit limited impact on anti-tensile properties. These findings reveal the correlation between sensor integration parameters and structural performance of flexible pipes, providing theoretical guidance for optimizing sensor integration processes in deep-sea flexible pipes.

The study focuses on the curing process and mechanical behavior of E44 epoxy resin in unconstrained structures. A Fiber Bragg Grating (FBG) sensor is used to monitor the temperature and strain of the resin in the thin-walled encapsulation structure in real-time. Based on curing kinetics, heat conduction, and viscoelastic models, the curing performance parameters and stress relaxation functions are derived, providing essential input data for the numerical simulation of epoxy resin curing behavior. The objective of the study is to develop a finite element simulation model for the epoxy resin encapsulation structure, taking into account residual stress and temperature effects, and to validate the model's accuracy by comparing it with experimentally measured temperature and strain data. The results show that the maximum temperature error does not exceed 10 %, and the maximum strain error is within 30 %, demonstrating the reliability of the analytical method and finite element model. This research provides testing and characterization methods, as well as theoretical support, for the cracking and interface debonding of epoxy resin under high and low-temperature cycling conditions.

In response to increasing demands for enhanced safety and weight reduction in modern aircraft, the development of high-strength, lightweight materials are still highly demanded. This study focuses on an ultra-high-strength titanium alloy with a tensile strength of 1 300 MPa, intended for use in critical lug. It is important to determine the tensile strength of the titanium alloy lug for its use in aerospace components. However, the applicability of the tensile strength formulas from the "Aircraft Design Manual" to this material remains uncertain, as does the tensile failure mechanism. Therefore, in this paper we design multiple titanium alloy lug configurations and perform tensile tests to determine the corresponding failure loads. Through the test results, the tensile strength formulas in the "Aircraft Design Manual" for titanium alloy lugs are updated. Combined with elastoplastic finite element analysis and experimental data, the tensile failure mechanism of the titanium alloy lugs is revealed.

With the rapid acceleration of population aging in China, the demand for feeding assistance among individuals with disabilities is becoming increasingly urgent. However, current feeding robots face several limitations such as poor adaptability to complex environments and safety concerns due to rigid structures. In this paper, a new six-degree-of-freedom feeding robot was developed that integrates obstacle avoidance path planning and compliance control. The robotic arm was designed employing a Bi-directional Rapidly-exploring Random Tree (Bi-RRT) algorithm to generate collision-avoidance trajectories, while inverse kinematics was solved using the Denavit-Hartenberg (D-H) parameter. At the control level, an impedance model-based compliance control strategy was introduced, and its compliant behavior under sudden external forces was verified through dynamic simulations. Prototype experiments demonstrated that the robot could effectively avoid obstacles and respond compliantly to external interference. While the robot achieved a 100% feeding success rate with solid and semi-liquid foods, it occasionally experienced spillage when feeding liquids due to structural limitations of the end-effector. This paper provides both a theoretical framework and practical guidance for enhancing the safety and environmental adaptability of feeding robots. Future work will focus on optimizing the end-effector design to further improve performance with liquid foods.

A study is conducted on the nonlinear dynamics of inclined flow pipes reinforced with graphene composite materials conveying fluid under two-phase flow conditions. Based on the von Karman nonlinear strain-displacement relationship and Hamilton's principle, the dynamic equations for inclined two-phase flow pipelines are established. The nonlinear dynamic model was solved using Galerkin method and fourth-order Runge-Kutta method to analyze the influence of the distribution pattern, weight fraction, and gas volume fraction of graphene platelets on the natural frequency and nonlinear dynamics of pipes conveying fluid. The experimental results show that the vibration amplitude of graphene reinforced pipes with V-shaped distribution is the smallest, followed by X-shaped distribution and A-shaped distribution. In addition, increasing the gas volume fraction can help alleviate fluid-induced vibration phenomena in pipelines. The above conclusion provides a theoretical basis for the application of graphene-reinforced inclined two-phase flow pipelines in practical engineering.

As a critical step in flexible electronics packaging, the ultra-thin chip peeling process plays a vital role in ensuring high-yield manufacturing. This study focused on mechanical behavior differences between two peeling methods: roller-stretching and needle-ejecting. A theoretical model of the "chip-adhesive-substrate" laminated structure was established and validated by finite element simulation. A dual-criteria safety criterion was proposed to quantify process safety based on the competing relationship between interfacial fracture energy of the adhesive layer and surface cracking stress of the chip layer, which overcame the limitations of traditional methods for quantitatively evaluating the safety of the peeling process. Results demonstrated that the needle-ejecting procedure outperforms roller-stretching in terms of the safety of ultra-thin chip peeling. The roller-stretching process only has high engineering application prospect for peeling large-sized and thick chips from soft and thick substrates. Furthermore, an innovative stretching-ejecting combination technology is proposed, introducing the concept of synergistic matching to achieve chip stress neutralization and fracture mode optimization. This research provides theoretical insights into non-destructive ultra-thin chip peeling technology, and delivers practical guidance for advancing high-yield flexible microelectronics packaging.