With the continuous advancement of composite manufacturing technology and the requirements of civil aviation for economy, the application of lightweight and high-strength composite structures in the aerospace field has gradually expanded from thin-walled secondary load-bearing structures to large-thickness, variable-section main load-bearing structures. The wide application of these complex composite structural parts has raised higher requirements for their manufacturing reliability verification. However, due to the anisotropy of the composite materials and the complexity of the shape of the aviation structure, defects such as delamination, pores, fiber waviness, and resin-rich layers are prone to occur during the manufacturing process of the main load-bearing composite structure. These microstructural anomalies significantly degrade the macro-mechanical performance of the composite components. Ultrasonic testing has become an important technology of defect detection in aerospace composite structures due to its high penetration, high sensitivity and good applicability. In this paper, we first introduce the types and characteristics of manufacturing defects in aerospace composite structures, focusing on the analysis of the causes of defects such as pores, delamination, fiber waviness and resin-rich layers and their effects on the mechanical properties of the structure. Then, the research progress of ultrasonic testing in the detection of single-type manufacturing defects and mixed-type defects in thin laminate and thick composite structures in recent years is reviewed. Subsequently, the application of artificial intelligence technology in the defect diagnosis of composite structure is discussed. Finally, the challenges faced by the current ultrasonic testing of aviation composite structures are analyzed, and the future development trend is prospected.

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.

Inspired by the nervous system of biological movement, Central Pattern Generator (CPG) control theory is applied to achieve various gait patterns in legged robots, which is of great significance in bio-inspired motion control. For the gait movement control of hexapod robots, the classical Van der Pol (VDP) oscillator model is first improved by adding a time proportion function to adjust the rising and falling phases of the periodic rhythm signal, enabling the regulation of the swing and support phases of the robot's legs. Next, the improved VDP oscillator is used as a functional unit, and the coupling delay between units is employed to regulate gait patterns, constructing a novel time-delay coupled CPG controller with a unidirectional loop. Furthermore, a hexapod robot model is designed in SolidWorks, and co-simulation experiments using ADAMS and MATLAB are conducted to achieve three common gait patterns: tripod, tetrapod, and wave gaits. Finally, gait tests are performed on a physical prototype to verify the feasibility and effectiveness of the proposed time-delay coupled CPG control system.

Chiral Liquid Crystal Elastomers (CLCE), with their ability to selectively reflect specific wavelengths of light and exhibit excellent large-deformation capabilities, have gradually become a promising flexible reflective display material. Studies show that the optical coloration properties of CLCE are closely related to local strain, displaying a significant force-optical coupling effect. As a soft material, CLCE possesses viscoelastic characteristics, resulting in a time-dependent mechanical response during deformation. However, systematic research on the optical and viscoelastic coupling properties of CLCE under uniaxial and biaxial deformation conditions remains limited. In this study, using a multi-axial opto-mechanical testing platform, we systematically investigate the time-dependent characteristics of the reflection spectrum of CLCE under uniaxial and equibiaxial deformation conditions. By analyzing the spectral properties under stress relaxation and different loading rates, we propose an improved phenomenological model for CLCE based on the stretched exponential viscoelastic constitutive relationship. This model provides theoretical support and experimental insights for further optimizing the application of CLCE in smart optical devices.

Low-frequency vibrations and noise levels are important indicators for evaluating automobile comfort. To address the issue of low-frequency vibrations and their control in automotive panel structures, we proposed a plate-type two-dimensional phononic crystal design based on the local resonance mechanism. The bandgap range of the phononic crystal was determined through the finite element method, and the mechanism of bandgap formation was analyzed. Subsequently, the transmission characteristics curve of the phononic crystal plate was calculated, and comparisons were also carried out for the vibration displacement. The results indicate that a complete bandgap appears in the plate within the frequency range from 62.48 Hz to 74.16 Hz. Within this frequency range, coupling effects between the base plate and the cylindrical resonators occur, leading to the formation of the bandgap. Elastic waves in the phononic crystal plate are successfully confined within the bandgap range. By adjusting the material and geometric parameters of the structure, the bandgap frequency range can be tuned to meet the requirements of more practical low-frequency applications. The structural design and analysis method proposed in this paper have broad application prospects in engineering fields such as low-frequency vibration reduction and noise control in automobiles.

In view of the high carbon emissions and limited land storage capacity in the eastern coastal areas of China, CO2 offshore geological storage holds significant application potential. Although the risk of CO2 leakage during offshore geological storage is extremely low, accurate assessment of CO2 diffusion in seawater under rapid leak scenarios is critical to ensure the safety of storage. Based on typical marine environment data, this study employs the Volume of Fluid (VOF) model to simulate the dynamic characteristics of CO₂ bubbles and utilizes the Euler model to simulate the diffusion characteristics of CO2 clusters in seawater, thereby completing a comprehensive simulation analysis of fluid dynamics. On this basis, a machine learning-based assessment method for subsea CO2 leakage is developed. The neural network model framework is constructed, and an inverse-problem solving model is established accordingly to analyze the morphological evolution and distribution range of CO2 leakage under different marine environmental conditions. Additionally, key parameters such as crack width and leakage velocity resulting from the leakage scenario are analyzed, enabling accurate calculation of the leakage amount. The prediction accuracy of this model can reach 95 %, demonstrating its effectiveness and applicability in addressing CO₂ leakage. This study not only offers an innovative method for rapid leakage assessment of CO2 offshore geological storage but also provides an important scientific basis and technical support for risk assessment and safety management in related fields in the future.

During the charge and discharge processes of solid-state lithium metal batteries, the stress generated at the interface between the rough surfaces of the lithium electrode and solid-state electrolyte plays a crucial role in the formation of lithium dendrites. In this paper, a mechanical model is established by considering the electrode and electrolyte as elastic bodies. Specifically, the stress at the interface of a two-dimensional sinusoidal rough interface is investigated for isotropic linear elastic materials. Using a two-dimensional Fourier transform, the relationship between stress and displacement at the interface in the transform domain is obtained. By applying the inverse transform and incorporating boundary conditions and interface continuity conditions, an analytical solution for the interfacial stress in two dimensional conditions is derived. When the wavenumber of surface roughness in one direction of the interface is zero, the two-dimensional interfacial stress solution degrades to the one-dimensional case. Subsequently, the analytical solution is used to analyze the influences of the material parameters of the electrolyte and electrode on the magnitude of the interfacial stress.

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 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.

Laminated beams are widely used in engineering structures due to their enhanced strength and stiffness. However, delamination, a barely visible form of damage, can occur during manufacturing or service. Accurate localization of delamination in laminated beams is essential for maintaining structural integrity. While the existing linear interface vibration model has been proposed to represent the absence of linear interface forces in the debonding region of open delamination, it fails to capture the opening-closing contact behavior of "breathing" debonding under nonlinear vibro-acoustic excitation. To address this problem, this study proposes a new nonlinear interface vibro-acoustic model, in which the nonlinear interface forces appear exclusively in the "breathing" debonding region, acting as multi-tone harmonic excitation sources to produce sideband harmonics. Moreover, this study emphasizes the use of nonlinear interface forces for the localization of delamination due to this inherent merit of localization. The nonlinear interface forces are reconstructed from nonlinear operating deflection shapes of a laminated beam. Nonlinear damage indices are established relying on nonlinear interfaces associated with multiple neighbouring sideband harmonics. The capability of the approach for localizing "breathing" debonding in laminated beams is experimentally validated through non-contact measurements using a scanning laser vibrometer. The results demonstrate that the approach is capable of predicting the occurrence of delaminations in laminated beams and accurately identifying their locations and sizes.

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 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.

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.

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.

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 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.

Damage identification is one of the most important aspects of structural health monitoring. In order to further improve the efficiency and accuracy of damage identification, a two-stage structural damage identification method based on the improved modal strain energy index and DBO-BP (Dung Beetle Optimization-Back Propagation) neural network is proposed. Firstly, the improved normalized damage index of modal strain energy is used for the damage localization analysis of the structure. Then, taking the average change rate of the structure unit modal strain energy as the input parameter, the stiffness reduction coefficient of the damaged unit as the output parameter, and utilizing the DBO algorithm which is an improved version of the optimal latin hypercubic method, the weights and thresholds of the BP neural network are optimized to perform the structural damage quantitative analysis. The concrete slab structure and flat rigid frame structure are used as exemplary models for damage identification verification. The results show that the proposed method is accurate in damage location identification, with high calculation efficiency for the degree of damage and small identification error as low as 0.4 %, exhibiting excellent damage identification performance.

By conducting tensile tests and numerical simulations on 304 stainless steel wire mesh/carbon fiber hybrid composite (SSWM/CFRP) laminates, the residual strength and failure modes of single hole specimens with different aperture sizes and double hole specimens with different circular hole arrangements were investigated. Digital Image Correlation (DIC) technology and Scanning Electron Microscopy (SEM) were used to observe the deformation and damage evolution characteristics of the specimens. The results indicate that the tensile stress-strain curve of SSWM/CFRP laminates with holes generally exhibits brittle failure characteristics. The residual strength of single hole specimens decreases with the increase of hole diameter, while the effective cross-sectional area of double hole specimens is affected by the arrangement of circular holes in the specimens. The DIC technology captures the maximum tensile and shear strains of a single hole specimen locally, which appear on the left and right sides of the circular hole along the diagonal direction. The constructed finite element model can effectively predict the residual strength and fracture path of the specimen, and reveal that the main failure modes of the specimen are ductile fracture of SSWM, fiber tensile damage of 0 ° fiber layer, matrix tensile damage of 90 ° fiber layer, and interlayer delamination damage.

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.

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.

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.

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.

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.

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.

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.

Column buckling is a critical topic in university-level Materials Mechanics courses and is widely regarded as a challenging subject to teach. In classical Materials Mechanics theory, the critical load is determined by analyzing the non-zero solution condition of the approximate equilibrium differential equation in the critical buckling state. Although this method is straightforward, it remains highly abstract and is difficult to apply to complex engineering stability problems. To enhance students' understanding of column buckling and its analytical methods, this study revisits the classical approach through the principles of virtual work and minimum potential energy. Additionally, based on the principle of minimum potential energy, the thermal buckling behavior of carbon nanotubes under a longitudinal linear temperature gradient is examined. This work aims to provide new perspectives for the teaching and research of column buckling, helping students gain a deeper comprehension of relevant concepts and methods in handling buckling problems.

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.

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%.

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.

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.

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.

To meet new detection requirements and achieve high sensitivity, microbeam-based biosensor technique faces challenges in the development of signal interpretation models. Through 3D finite element simulations of the detected quasi-static signals of microbeam under surface adsorption, we revealed an asymmetric distribution characteristic of the microbeam cross-section's warping. However, the existing theoretical models considering shear deformation cannot accurately describe this asymmetric warping. To address this issue, first, we simplified the complete adsorption of molecules as a uniformly distributed surface stress acting on the microbeam's surface and obtained the distribution pattern of warping zero point through 3D finite element simulation. Then, we employed the semi-inverse method of plane elasticity theory to determine the shear stress distribution and shear force that correspond to the asymmetric warping characteristics on the deformed cross-section. This led to an improvement in Timoshenko beam theory and the establishment of a new model to predict the detected quasi-static signals of microbeam. Finally, we validated the analytical model by comparing with experimental results and finite element simulations. The results indicate that the predictions of our improved model agree well with the relevant microbeam experiments. Moreover, within the geometric size ranges employed in the existing adsorption-microbeam static experiments (length-to-thickness ratio of 200-500, length-to-width ratio of 3-7), its prediction error for the microbeam's free-end deflection is less than 3 %, which is smaller than that of other theoretical predictions. Additionally, the shear effect and axial force effect negatively impact the microbeam's deflection, with the shear effect having a significantly greater influence than the axial force effect. This model and its conclusions provide a new perspective for interpreting the static detection signals of microbeam biosensors and developing the relevant design.

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.

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.

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.

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.