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.

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.

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.

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).

Zirconium alloys are extensively utilized in nuclear reactor fuel cladding and other critical applications due to their superior mechanical properties and corrosion resistance. However, under nuclear irradiation, the formation of voids within the material markedly deteriorates its mechanical performance and service reliability. In this study, a rate-dependent crystal plasticity constitutive model suitable for hexagonal close-packed (HCP) zirconium alloys is developed and implemented based on the Crystal Plasticity Finite Element Method (CPFEM). The model is realized numerically through a UMAT subroutine integrated into the Abaqus platform. A single-crystal Representative Volume Element (RVE) model containing spherical voids is employed to systematically investigate the macroscopic mechanical response and microscopic void evolution under various loading conditions, including uniaxial and biaxial tension and compression. The results demonstrate that porosity plays a dominant role in governing the strength and damage evolution of zirconium alloys. Specifically, under uniaxial tension, void growth induces a pronounced softening effect, whereas under uniaxial compression, void shrinkage results in geometric hardening, leading to a continuous increase in flow stress with deformation. Moreover, the initial crystallographic orientation exerts a critical influence on the macroscopic anisotropic behavior: as the loading direction rotates from the 〈a1〉 axis to the 〈c〉 axis, the material exhibits higher yield strength and elastic stiffness due to the limited activation of slip family along the c-axis. Further analysis indicates that the multiaxial stress state profoundly alters the void evolution behavior—biaxial tension accelerates softening failure, while biaxial compression enhances hardening. This work elucidates the coupled effects of void evolution, crystallographic orientation, and loading path on the mechanical response of zirconium alloys, providing theoretical guidance for structural integrity assessment and performance optimization under complex stress states.

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.

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.

Polymers and their composites, with excellent mechanical properties and high designability, are widely used in traditional engineering and emerging fields. However, exposure to complex multi-field coupled environments (e.g., hygrothermal conditions, chemical corrosion, electromagnetic radiation, and cyclic loads) can induce nonlinear behaviors in materials, such as performance degradation and anisotropic damage evolution. This paper first sorts out several classical polymer constitutive models and analyzes their advantages and limitations. Secondly, it focuses on the research progress of composite damage constitutive models under multi-field coupling, elaborating on the model construction approach, definition of damage internal variables, micro-macro mechanisms of damage evolution, and quantitative characterization methods for coupling effects, with emphasis on the analysis of the advantages and disadvantages of continuum damage mechanics in describing multi-field coupling and cross-scale damage behavior. Finally, it prospects the key future research directions of composite damage mechanics, providing references for theoretical breakthroughs and engineering applications in related fields.

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.

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.

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.

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.

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.

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.

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.

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.

Low-dimensional nanocomposites have attracted significant attention in the area of solid-state battery and aerospace engineering, due to their superior mechanical properties while maintaining lightweight. The mechanical behaviors of low-dimensional nanocomposites are characterized by the multi-field coupling and multi-scale features while operating under complex environments in practical applications. In this research, the multi-field coupled mechanics of low-dimensional nanocomposites are systematically reviewed from the experimental, theoretical, and numerical aspects. The recent progress can be divided into three parts: grain size dependent elastoplasticity, temperature-dependent viscoelasticity, and temperature-dependent viscoplasticity. Microscopic characteristics, such as temperature effects, dislocation, interface effect and microstructural evolution, are connected with the macroscopic multi-field coupled behaviors via the multi-scale models. Finally, the existing issues and prospectives in the research of multi-field coupled mechanics of low-dimensional nanocomposites are summarized.

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.

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%.

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.

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.

To address the mechanical response and structural design challenges of composite turbine blades under complex service environments, this paper takes a high-temperature alloy turbine rotor blade as the reference prototype and conducts an integrated design of SiCf/SiC composite turbine blades from the perspectives of manufacturing process, structural configuration, and performance. First, a three-dimensional finite element model of the blade-disk assembly is established, and a coupled analysis considering centrifugal, thermal, and aerodynamic loads is performed to systematically evaluate the stress distribution and deformation characteristics of the overall blade. Subsequently, the load distribution characteristics of the blade root under realistic operating conditions are extracted and equivalently applied to a local blade root analysis model. In conjunction with the forming characteristics and fiber continuity requirements of SiCf/SiC composites, multiple blade root layup design schemes are proposed. Local mesoscale finite element models of the blade root region are developed, and a comparative analysis of radial stress and interlaminar shear stress distributions among different layup configurations is carried out. The results identify the staggered insert ply as the optimal scheme, demonstrating that it can effectively enhance the structural strength margin of the blade while significantly reduce  the interlaminar shear stress level in the blade root region.

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.

Fatigue failure is one of the most common and highly hazardous forms of failure in engineering structures. Traditional fatigue prediction methods often rely on phenomenological selection of damage variables, lacking exploration of physical mechanisms, which necessitates further research. This study begins with an analysis of the energy evolution characteristics of materials and formulates a thermodynamically self-consistent constitutive equation to calculate the real-time mechanical dissipation rate of materials under external loads. Leveraging its non-negative nature, the dissipation is used to characterize damage accumulation. Through a constitutive model that does not include internal damage variables, the evolution of stress and strain is described while simultaneously quantifying damage and predicting fatigue life. Using TA19 titanium alloy as the target material, systematic finite element simulations and experimental comparisons were conducted on four different borehole plate (BHP) specimens with varying aperture sizes under asymmetric triangular wave loading at 535 MPa with a stress ratio of 10∶1. The results demonstrate that the proposed method not only accurately captures stress concentration and plastic evolution at the notch root but also predicts fatigue life in close agreement with experimental data, with errors confined within the engineering-acceptable two-fold scatter band. Furthermore, the simulation results reveal that mechanical dissipation exhibits a monotonically increasing trend during the fatigue process, further validating its rationality and stability as a damage metric. This provides a novel approach and methodology for quantitative analysis of fatigue damage and life prediction.

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.

In rotating Rayleigh-Bénard convection systems, self-organized vortices serve as the fundamental structures of flow, and their interactions dominate the transport properties of the system. Combining experimental observations with statistical physics theory, this study reveals a dynamic transition of the vortex system from a disordered random state to a hyper-fluctuating state as the reduced Rayleigh number Ra/Rac decreases. Analysis of density fluctuations demonstrates that significant giant number fluctuations emerge under strong rotational constraints, characterized by a power-law exponent exceeding that of a random Poisson distribution. Results from the static structure factor S(k) indicate that while the vortex system lacks global long-range periodicity, it exhibits high local ordering that closely resembles a hexagonal lattice pattern. Further analysis based on spatial correlation functions and cluster statistics reveals that hydro-dynamic interactions and steric effects among vortices induce local anisotropy, facilitating the formation of large-scale vortex clusters with self-similar characteristics (L ~ N0.65). The long-range correlations inherent in these cluster structures are identified as the physical origin of the hyper-fluctuating phenomenon. This research elucidates the complex statistical properties of vortex systems, providing a novel physical perspective for understanding the collective behavior and structural phase transitions of self-organized structures in turbulent convection.

Tensegrity robots, characterized by their lightweight structure, deformability, and superior structural adaptability, exhibit broad application potential in fields such as planetary exploration and disaster rescue. Existing research on the actuation and control strategies for tensegrity robots has primarily followed the principle of minimizing the number of active cables. That is, in the design of the robot's actuation control, if contracting a single cable can induce motion, that cable is preferentially actuated while others remain inactive. This approach often requires a large contraction length of the single cable, which in turn leads to a longer response time in actuation control. As a result, the robot suffers from low locomotion efficiency, limiting its practical engineering applications. In this study, we take a three-rod tensegrity robot as the research subject. Based on the force density method, a systematic model of the tensegrity geometry and static equilibrium properties is established, and the relationship between force application and structural deformation is analyzed. Furthermore, by employing a rolling criterion based on center-of-gravity shift, a traversal search algorithm is designed, and a control strategy based on multi-cable coordinated actuation is proposed. This strategy reduces the required contraction length of any single cable, thereby decreasing the magnitude of structural deformation during motion and significantly shortening the response time of the actuation system. Finally, an experimental platform for the three-rod tensegrity robot, controlled by an ESP32-based system, is developed. Prototype experiments validate the effectiveness of the proposed strategy. The results demonstrate that, compared to the minimal-cable actuation strategy, the coordinated multi-cable actuation mode can notably reduce deformation amplitude and shorten response time.

In the precursor impregnation pyrolysis (PIP) process for fabricating ceramic matrix composites, the impregnation efficiency is significantly affected by the viscosity of the precursor solution, which depends on the impregnation temperature, solute mass fraction, and shear rate. In this study, a five-parameter apparent viscosity model based on the Arrhenius form is developed to describe the dependence of viscosity on temperature, solute concentration, and shear rate. The model parameters are calibrated and validated using polycarbosilane (PCS) precursor solutions mixed with ceramic powders and different solvent types. The sensitivity of viscosity to temperature, shear rate, and PCS mass fraction is analyzed. Based on the established model, a capillary infiltration relation is derived to describe the penetration depth of the precursor as a function of solute mass fraction, temperature, and impregnation time. The results demonstrate that the proposed model quantitatively captures the influence of key factors on precursor viscosity and provides a theoretical basis for optimizing solution formulation and impregnation process parameters in the PIP method.

Damage evolution at the mineral scale determines the macroscopic mechanical behavior of rock materials. Voronoi polygons were employed to characterize rock minerals, while an interface model was used to describe the weakening effects of mineral boundaries. A mineral-scale damage simulation method was developed within the framework of the elastoplastic phase-field method, and its validity was verified through simulations of triaxial compression tests on granite. Based on the multiscale energy transfer theorem, a mineral-scale energy statistical analysis method was proposed. A macroscopic damage variable for the rock was defined by integrating the strain energy density of mineral particles, and the damage mechanism of the rock was explored from the perspective of energy evolution in mineral particles. The results indicate that strain and stress concentrations cause the data distribution of strain energy density in mineral particles to exhibit right-skewness, which can be well described by a lognormal distribution. The mean parameter of the lognormal distribution of mineral strain energy density can be determined by the macroscopic homogenized strain energy density and the variance parameter, with the variance parameter increasing approximately linearly with the macroscopic damage variable.

This paper investigates the free vibration of open cylindrical shells on fractional-order viscoelastic foundations. A fractional-order viscoelastic standard linear solid foundation model is introduced, and the free vibration equations of the open cylindrical shell on this foundation are established. Based on the one-dimensional Euler-Bernoulli beam and circular arch curved beam models, an approximate solution for the vibration modes of the open cylindrical shell is constructed. The vibration attenuation induced by the viscoelastic foundation is simulated using the complex frequency hypothesis. The proposed method is compared with literature through numerical examples, validating its feasibility. Additionally, the influences of the fractional-order coefficient and viscosity coefficient of the fractional-order viscoelastic foundation on the natural frequency and vibration attenuation of the cylindrical shell are discussed.

The vibro-acoustic characteristics of submerged shells are crucial for understanding vibration propagation and sound radiation mechanisms. Research on vibration and acoustic radiation characteristics of submerged shell structures, based on conventional frequency-domain analysis methods, has gained significant attention due to its ability to accurately identify quantify modal contributions and line-spectrum noise. However, the relationship between their radiation characteristics and elastic waves has not been clearly disclosed. In the present paper, a typical submerged shell structure is employed as the demonstration model. Finite element method and spatial Fourier transform method are integrated for the vibro-acoustic systems so as to identify the elastic waves within shell structures and their corresponding radiation bright spots. Using typical structural examples with different foundation forms, the numerical results reveals that the characteristics of radiation bright spots in the wavenumber domain are significantly affected by the structural symmetrical schemes. Furthermore, the correspondence between the frequency domain and the wavenumber domain is developed, which is based on spatial wavenumber spectra and key parameters such as the shell's normal vibrational velocity, far-field radiated waves, and radiated sound power. The numerical results demonstrate that increasing foundation symmetry helps reduce the acoustic radiation level of combined shell structures, providing new theoretical support for subsequent structural optimization design.

Delamination, as a typical form of invisible damage in composite laminates, can significantly affect structural performance and safety. However, detecting small initial delaminations using conventional linear dynamic imaging methods is highly challenging due to their minimal impact on structural stiffness. Conversely, delaminations exhibit "breathing"-like opening-closing behaviours during vibration, leading to contact and separation of interfaces. This phenomenon introduces nonlinear characteristics in interlaminar normal and shear stresses. In this study, these stresses distributed across the breathing delamination interfaces are defined as nonlinear interfacial stresses (NISs), which exist within delamination regions only and can be decomposed into a series of components at the frequencies corresponding to the higher harmonics. A novel method for imaging delaminations is proposed in this study. Amplitudes of the NIS are reconstructed using nonlinear steady-state wavefields corresponding to the higher harmonics, and delamination indices suitable for nonlinear dynamic imaging of small initial delaminations are established by taking advantage of this localized nature. Experimental results reveal that the proposed delamination imaging method is not only effective for large-area thermal delaminations but can also accurately characterize small delaminations caused by inherent defects or low-speed impacts.

Based on the classical laminated plate theory, this study investigates the buckling problem of Variable Angle Tow (VAT) composite laminates with multiple cutouts by employing the finite cell method and isogeometric analysis. The buckling behavior of such laminates with various cutout shapes, sizes, and numbers is analyzed. Comparisons with existing literature or finite element results are conducted to verify the convergence and accuracy of the proposed method in addressing the buckling of VAT composite laminates with multiple cutouts. Furthermore, a parametric buckling analysis is carried out for VAT composite laminates with single or multiple cutouts under different boundary conditions and fiber paths. The results indicate that reasonable fiber angles can significantly minimize the loss of buckling performance induced by cutouts.

In practical applications, plate-type floating structures are challenged by complex marine environments such as wind, waves, and currents, and their motion stability needs further improvement. To address this, this paper proposes an improved plate-type floating structure with vertical baffles, calculates its interaction with waves, and focuses on studying the motion response of the structure under different baffle configurations, geometric parameters of the floating body, and wave periods. A comparison is also made between plate-type floating structures with fixed and articulated vertical baffles. The study shows that increasing the height of the baffles can effectively reduce heave and pitch motions in short floating structures. When the vertical baffles are located at the rear of the buoyancy tank, the heave and surge motions are most stable, while the pitch motion reaches its maximum. Additionally, vortex dissipation can mitigate the influence of waves on the heave and surge motions of short floating structures. It is hoped that the research findings will provide a reference for engineering design and practical applications.

The equivalent bending stiffness model for an open crack has attracted great attentions, since it has accounted for the effect of stress concentration and the influence of the crack on the stiffness along the beam. Researchers commonly adopted  the equivalent stiffness equations from a paper authored by the model creator. It has been found that there are mistakes in the equivalent stiffness equations (referred as Model 1). Meanwhile, it is noted that Model 1 has been simplified by use of an approximate equation. However the detailed derivation and applicable range have not been given in the literature. At first, the equivalent stiffness equations are rederived in a rigorous way by use of energy method based on the fracture mechanics theory for a rectangular-sectional beam with an open crack subjected to a pure bending moment, and this model is designated as Model 2. Then by using an approximate equation to simplify the modified crack model (namely Model 2), Model 3 is obtained. Next, the approximate equation used to simplify the crack model is verified. Finally, these three models are employed to calculate the stress and strain of a rectangular cross-section beam with open cracks of different severities  occurring at different locations. An analysis is conducted on the approximate expression's prerequisite (i.e., the crack is not near the ends) and applicability. The three crack models are compared by evaluating the predictions of the equivalent stiffness distribution along the beam.

The rheological properties of prestressed duct grouting material directly influence grout compactness and structural durability, with ambient temperature and fly ash content being key factors governing its flow behavior. Addressing the limitation of existing studies, which often focus on single variables and lack multi-field coupled constitutive models, this paper develops a rheological constitutive model for grouting material under the combined effects of fly ash content, temperature, and shear rate. The model is based on the Ostwald-de Waele power-law model, incorporates a three-parameter modified Arrhenius equation to characterize the temperature dependence of apparent viscosity, and integrates a mixture rule from composite mechanics to account for fly ash incorporation. Validation against experimental data from the literature demonstrates that the proposed model effectively predicts shear stress responses under various conditions. At a constant shear rate, increasing the temperature from 5 ℃ to 50 ℃ reduces shear stress by approximately 27.5%. Raising the fly ash content to 20% further decreases shear stress by over 34%, significantly enhancing slurry fluidity. Under the synergistic effect of elevated temperature and high fly ash dosage, the maximum shear stress reduction reaches 61.5%. This research provides theoretical support for the design and construction control of high-performance grouting materials under the complex environmental conditions of port areas.

To reveal the dynamic response characteristics and damage mechanisms of chlorinated polyvinyl chloride (CPVC) cable protection pipes under standardized drop-weight impact, this study conducted a series of drop-weight impact tests to systematically measure the dynamic strain and damage patterns of pipe specimens from different performance batches under varying impact energies. Subsequently, a three-dimensional explicit dynamic finite element model of the drop-weight impact was established, and its accuracy was validated using the experimental data. With the aid of this model, the dynamic response behavior of the pipe during impact was analyzed in depth. The variation trends and magnitudes of key physical quantities, including impact force, strain, strain rate, contact stress, and energy dissipation, were systematically examined. By correlating these results with the damage characteristics of pipes from different performance batches, the dominant factors governing impact-induced damage were identified. Ultimately, the study elucidates the dynamic response patterns and damage mechanisms of CPVC protection pipes under impact loading. The extracted key physical indicators provide theoretical foundations and evaluation criteria for the development of portable on-site inspection equipment.