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Establishment of the damage tolerance criterion of projectile-borne electronics in the high-g extreme environment

Weilong Yang, Qiming Liu, Tao Li, Xu Han

Accepted Manuscript , doi: 10.1016/j.taml.2026.100653

[Abstract] (0) [PDF 2657KB] (0)

Abstract:
Projectile-borne electronics are essential components for precision-guided munitions. However, they are subjected to a complex overload environment characterized by high-frequency vibrations, high temperatures, and high pressures during launch. Evaluating overload damage presents a significant challenge. Consequently, this study aims to establish a damage tolerance criterion for projectile-borne electronics in high-g extreme environments using impact overload tests and high-precision numerical simulations. Initially, an impact overload test device was designed and implemented, considering the guidance segment and chamber firing characteristics, to ascertain the overload damage characteristics of projectile-borne electronics. Subsequently, a simulation model incorporating projectile-borne electronics was established and validated to identify the most vulnerable regions and critical overload responses under various conditions. Based on the simulation data, the overload damage tolerance curve was established using a power function regression fitting method. Leveraging the concept of impulse equivalence, the damage tolerance criterion for the high-g extreme environment was formulated. The criterion’s accuracy and practicality were further verified through experimental damage results of electronic components. This study provides a practical design foundation for the anti-high-overload design of projectile-borne electronics.

Casting computational fluid mechanics into a convex quadratic optimization framework

Hussam Sababha, Haithem Taha, Mohammed Daqaq

Accepted Manuscript , doi: 10.1016/j.taml.2025.100651

[Abstract] (31) [PDF 2204KB] (0)

Abstract:
We employ the principle of a minimum pressure gradient to transform problems in unsteady computational fluid dynamics (CFD) into a convex optimization framework subject to linear constraints. This formulation permits solving, for the first time, CFD problems efficiently via well-established quadratic programming tools. The proposed approach is demonstrated via three benchmark examples. In particular, through comparison with traditional CFD tools, the proposed framework is capable of predicting the flow field in a lid-driven cavity, in a uniform pipe (Poiseuille flow), and that past a backward facing step. The results highlight the potential of the method as a simple, robust, and potentially transformative alternative to traditional CFD approaches.

Continuous image representation based on deep learning for reducing interpolation bias in DIC

Wang Lianpo, Lei Zhaoyang

Accepted Manuscript , doi: 10.1016/j.taml.2025.100652

[Abstract] (44) [PDF 2197KB] (0)

Abstract:
After more than forty years of development, the accuracy of digital image correlation (DIC) methods has reached an extremely high level. However, the interpolation bias of DIC has not been resolved. With the flourishing of deep learning in the field of image superresolution, it has become possible to use deep learning-based image superresolution methods to reduce DIC interpolation bias. To achieve this goal, this paper improves the local implicit image function (LIIF) method based on the characteristics of speckle images to obtain LIIF-S, achieving continuous image representation and arbitrary resolution interpolation. Subsequently, LIIF-S is used as the interpolation algorithm of the inverse compositional-Gaussian Newton (IC-GN) method to reduce the interpolation bias. The simulation experiment results show that LIIF-S not only improves the accuracy by more than one order of magnitude compared to traditional interpolation algorithms but also that the interpolation bias does not have sinusoidal characteristics. In addition, the effectiveness and generalization of the LIIF-S method in unseen real-world scenarios have also been demonstrated through physical experiments. The code and dataset are publicly available at https://github.com/LianpoWang/SLIIF.

Shock wave propagation of nest-like structures under axial impact

Liu Chang, Peng Qing, Wei Yueguang, Liu Xiaoming

Accepted Manuscript , doi: 10.1016/j.taml.2025.100649

[Abstract] (40) [PDF 1630KB] (1)

Abstract:
Inspired by natural bird nests, nest-like structures consist of randomly packed slender particles confined within a container. This study investigates the dynamic behavior of nest-like structures by finite element simulation and a shock model. Under dynamic impact conditions, the nest-like structures exhibit distinct mechanisms compared to quasistatic loading. A confined deformation zone with nearly uniform stress forms near the loading end. This zone propagates steadily into the undeformed region at a constant velocity. Notably, the expansion speed exceeds the loading rate but remains significantly slower than the stress wave speed in solid material. We proposed a rigid-perfectly plastic-locking (R-P-P-L) shock model to quantitatively establish how initial conditions govern two critical dynamic responses: the stress in the confined zone and the expansion velocity of the confined zone. These dynamic characteristics of nest-like structures demonstrate their potential for impact resistance.

Thermomechanical treatment influence on the copper wire microstructure evolution

Andrey Volokitin, Irina Volokitina, Zoya Gelmanova, Anastassiya Denissova

Accepted Manuscript , doi: 10.1016/j.taml.2025.100650

[Abstract] (43) [PDF 1657KB] (0)

Abstract:
This paper presents a new technology for copper wire processing. This technology involves deforming the wire in a rotating equal-channel stepped matrix, after which the workpiece is subjected to a drawing operation. As a result of the deformation of the copper alloy wire via this technology and subsequent annealing at 400°C, a gradient microstructure with improved mechanical properties was obtained. Annealing after deformation is carried out to stabilize the formed submicrocrystalline structure, isolate dispersed strengthening particles and increase the electrical conductivity. The surface zone is crushed to 400 nm, and the intermediate zone is crushed to 2 μm. Then, the grain size increases further toward the central part of the wire and is 22 μm. The generation of a gradient-symmetrical microstructure was confirmed via microhardness tests. Thus, our method, which combines twisting in a rotating matrix and drawing, is a promising tool for obtaining materials with improved mechanical properties. It allows reducing drawing forces, obtaining a gradient structure of the material and increasing its plasticity.

A regularization technique for accurate reconstruction of numerical solution of wave propagation problems

Salvatore Lopez

Accepted Manuscript , doi: 10.1016/j.taml.2025.100648

[Abstract] (41) [PDF 9674KB] (0)

Abstract:
In the numerical solution of wave propagation problems, spurious oscillations occur in the exact time integration of the related equation of motion. This is due to the high frequencies introduced by the spatial discretization, given the small size of the mesh elements and the integration step required to capture the wave phenomena. Currently, an answer to this problem is given by the use of the smoothing properties, intrinsic to the scheme or obtained through artificial viscosity, of dissipative time integration methods. More recently, in an alternative approach to the problem, the solution has been regularized via a post processing smoothing technique. In particular, on the basis of an initial nondissipative scheme, at a fixed observation time a series of steps of an appropriate dissipative time integration method achieves the desired smoothing. However, in both approaches, as the dissipative steps are performed, the noise progressively decreases, but the important values related to the peak regions of the solution degrade significantly. Here we describe a regularization process that automatically returns a solution where the noise has been eliminated but does not affect the significant regions of the solution. The presented technique recognizes the flat or peak shapes of the original solution among the oscillating components representing the noise. Operationally, the presented algorithm, starting from a nondissipative step-by-step scheme for time integration, iteratively smooths the related kinematic quantities and finally recovers the regularized solution as a suitable composition of smoothed and unsmoothed subdomains.

Nonlinear coupling from acoustics to aerodynamics in perforated plates at normal incidence

Sylvain C. Humbert

Accepted Manuscript , doi: 10.1016/j.taml.2025.100647

[Abstract] (40) [PDF 3584KB] (0)

Abstract:
This study addresses the mean nonlinear pressure loss through a perforated plate caused by the combination of the steady bias flow itself and high-amplitude acoustic excitations. An analytical treatment of this problem yields an explicit formula allowing one to estimate the mean flow resistance as a function of the steady flow velocity and unsteady velocity amplitudes. An increase in the unsteady velocity amplitude(s) yields an increase in the mean flow resistance, which highlights the presence of nonlinear coupling from acoustics to aerodynamics. For a given value of the mean flow velocity (or pressure drop), this causes an increase in the mean pressure loss (or a decrease in the steady flow velocity). The model highlights that for moderate acoustic disturbances, the mean flow and acoustic contributions to the mean flow pressure loss add up, whereas for large acoustic velocity amplitudes, the pressure loss is, to the leading order, proportional to the product of the mean flow velocity and the maximum acoustic velocity amplitude. Finally, the model is exploited to explain the presence in some acoustic studies of a valley in the acoustic resistance curve versus the acoustic velocity amplitude. The simplicity of the model makes it attractive to account for 1D flow oscillation effects in fluid flow network models, to understand the essential mechanisms at play in the acoustically induced increase in the mean flow resistance, and to take this phenomenon into account when estimating the acoustic impedance of perforated plates.

Experimental study on the effects of joint span and shape on crack initiation and propagation in PMMA plates by the caustics method

Zhang Houtian, Wang Qishen, Lei Jianyin, Qiu Peng, Liu Zhifang, Wang Zhihua

Accepted Manuscript , doi: 10.1016/j.taml.2025.100646

[Abstract] (58) [PDF 2113KB] (0)

Abstract:
This study employed a dynamic caustics system integrated with a Hopkinson pressure bar, Schlieren optics, and a high-speed camera to investigate how joint span and shape affect crack initiation and propagation. First, crack penetration into joints with different spans (10 mm, 30 mm, 50 mm) and different shapes (“u” and “n”) was visualized. Then, crack-tip stress intensity factors and propagation velocity were measured by high-speed caustics patterns. Finally, fractal dimensions of crack trajectories were obtained to quantitatively evaluate the complexity of the crack layout. Based on loading time, the crack behavior is divided into 4 phases: first precrack initiation, propagation toward the joint, secondary initiation from the joint and final propagation toward the boundary. Since the phase 1 duration increases with span, crack initiation from precracks clearly depends on span length. In phases 2 and 3, reflected waves occur from the joint interface; furthermore, they are confirmed to be Rayleigh waves through wave velocity. Meanwhile, the reflected Rayleigh waves from the “n”-shaped joint have a significant effect on crack propagation in phase 2. In phase 4, crack trajectories initiating from joint ends are heavily influenced by joint span, which is associated with crack interaction. Furthermore, different opening orientations (“u” and “n”) of arc-shaped joints have different effects on crack behavior. The “u”-shaped joint exhibits crack behavior similar to that of same-span line-shaped joints. The “n”-shaped joint demonstrates a strong fracture resistance. This work advances the understanding of fracture resistance as influenced by joint span and shape variations.

A hydraulic fracture and natural fracture interaction criterion considering the influence of intermediate principal stress and T-stress

Haifeng Zhao, Wang Zhang, Hongwei Shi, Hong Guo

Accepted Manuscript , doi: 10.1016/j.taml.2025.100645

[Abstract] (56) [PDF 1430KB] (1)

Abstract:
Highlights of the StudyUnconventional reservoirs such as shale and tight sandstone exhibit low porosity and low permeability. By applying horizontal wellbore fracturing techniques, a fracture network with a certain degree of complexity can be created within the reservoir to enhance oil and gas recovery. The interaction between hydraulic fracture(HF) and natural fracture(NF) plays a crucial role in determining the complexity of the fracture network. This study examines the interaction process between HF and NF, using the unified strength theory as the fracture initiation criterion for the fracture on the opposite side of natural fractures, and considering the influence of T-stress on the radius of the nonlinear zone. An interaction criterion that accounts for both intermediate principal stress and T-stress effects is proposed, and the predictions are highly consistent with experimental results. The results of the sensitivity analysis indicate that T-stress influences the critical radius of the nonlinear zone, thereby causing disturbances in the magnitude of induced stress. With T-stress taken into account, the extent of the penetration zone increases, and the extent of the opening zone decreases. However, at high approach angles, the influence of T-stress diminishes. As the Poisson’s ratio, cohesion, and fracture toughness increase, the tensile strength decreases, making HF more likely to penetrate NF, resulting in a single fracture morphology. A lower stress differential and a lower tensile-to-compressive ratio promote the opening of natural fractures. Additionally, as the intermediate principal stress coefficient increases, the ranges of the opening and slip zones expand, while the penetration zone shrinks.

Analysis of bilateral constrained sliding contact problems with variable friction coefficients via a cumulative frictional dissipation approach

Ling Tao, Ling Wang, Ning Hu, Shaowei Tong, Hong Wen, Qingshui Qiu

Accepted Manuscript , doi: 10.1016/j.taml.2025.100641

[Abstract] (80) [PDF 0KB] (0)

Abstract:
This work investigates the bidirectional relationship between contact mechanics and frictional wear behavior in bilateral constrained sliding contact. An internal state variable representing the contact surface condition is incorporated into the Coulomb friction law to account for wear phenomena. A contact detection method has been constructed to identify the positional relationship between two elements during contact, leveraging vector-related features of the vertices on the contact area between the slideway and the slider. A bipotential function for rigid bilateral constraints is formulated by introducing a stability factor. Combining the potential-Coulomb contact force model, a numerical algorithm is developed for variable friction contact problems on the basis of cumulative frictional dissipation and is initially implemented for rigid body bilateral contact problems. The algorithm is subsequently applied to bilateral constraint analysis in a sliding mechanism under both constant and variable friction conditions, and the influences of the wear and contact clearance factors are studied. The numerical results demonstrate consistency with energy conservation principles and dynamic laws, validating the effectiveness of the proposed algorithm. This work extends the applicability of the bipotential function approach and provides a theoretical foundation and analytical tools for optimizing bilateral nonideal contact structures and predicting equipment service life.

Effect of prestress on the impact performance of a fully clamped metallic beam: analytical modeling and numerical simulation

Ren Jianwei, Gao Huiyao, Li Xue, Zhao Zhenyu, Zhang Daqiao, Wu Jian, Li Bangjie, Lu Tian Jian

Accepted Manuscript , doi: 10.1016/j.taml.2025.100644

[Abstract] (67) [PDF 0KB] (0)

Abstract:
Metallic protective structures (e.g., beams and plates) are widely used against impact and blast loadings. Their precise dynamic responses are critical for design and service, especially when unintended preloading or prestress caused by accidental deformation is present. In this study, the effects of prestress on the structural deformation and springback behaviors of a fully clamped metallic beam subjected to a subsequent impact load are systematically investigated. A combined research approach, consisting of analytical modeling constructed by a simplified string-hinge model (SSHM) that accounts for the roles of structural hinge and string components as well as double-solver coupling numerical simulation incorporating implicit and explicit solvers simultaneously, is employed, which is validated against existing experimental results. The influence of material strain hardening is considered. The presence of prestress can improve the impact resistance of a beam by reducing its peak deflection and increasing the structural springback of the beam, owing mainly to altered beam geometries and, initially, the stress state as the beam is deformed. Using the analytical modeling of the SSHM, the roles of the components of the hinge and string under various loading scenarios are subsequently delineated, particularly in terms of the development process of the mechanical performance of each component within the out-of-plane deformation and springback stages. During the deformation process of the impacted target, the roles of the bending moment and membrane force vary with increasing midspan deflection. These roles also change when the pretension intensity is increased.

Topographic control of gyre dynamics under thermal and wind forcing in rotating stratified systems

Koue Jinichi

Accepted Manuscript , doi: 10.1016/j.taml.2025.100643

[Abstract] (65) [PDF 0KB] (0)

Abstract:
Topographic features exert fundamental control on large-scale oceanic circulation, yet their role under the combined influence of thermal and wind forcings remains insufficiently understood. Here, rotating tank experiments in stratified fluids are employed to investigate how slopes and depressions modulate gyre dynamics. Thermal forcing alone generated seasonally reversing surface circulations: summer heating induced robust counterclockwise gyres, whereas winter cooling produced clockwise circulation. These seasonal patterns were amplified near slopes and depressions owing to localized heat retention. In tanks with depressions, surface velocities weakened, giving rise to seasonally reversing, localized vortices. Under wind forcing, persistent counterclockwise gyres developed, with their centers displaced offshore by spatial heterogeneity in wind stress. Depressions generated pressure minima that drew fluid inward, producing centrally confined counterclockwise eddies shaped by the Coriolis force. When thermal and wind forcings act simultaneously, gyres markedly intensify, resulting in enhanced vorticity near the thermocline and flow suppression at depth due to stratification. Strikingly, the observed velocities exceeded the linear superposition of the individual forcings, demonstrating a nonlinear interaction. These results underscore the decisive role of small-scale topography in modulating rotating, stratified flows and provide mechanistic insights into the dynamics of basin-scale circulation in natural water bodies.

Magnetic potential tuning in a typical piezoelectric energy harvesting system: bistable versus Tri-stable capability under initial-state sensitivity

Shang Huilin, Shen Yi

Accepted Manuscript , doi: 10.1016/j.taml.2025.100642

[Abstract] (64) [PDF 3153KB] (0)

Abstract:
This study presents a theoretical framework for analyzing a magnetically coupled multi-stable piezoelectric energy harvesting (PEH) system, comparing bistable and tri-stable configurations under initial perturbations. Through static bifurcation analysis, extended averaging, and numerical simulations, we reveal how nonlinear dynamics such as saddle-node bifurcations, chaos, and fractal basins of attraction (BAs) collectively influence efficiency. A magnetic coordination mechanism enables controlled switching between bistable and tri-stable potentials by adjusting the magnet spacing and vertical separation, challenging the conventional superiority of tri-stable designs. Specifically, the bistable system outperforms at low excitation amplitudes because of lower interwell thresholds, whereas the tri-stable setup excels only near trivial equilibria or within a moderate high-amplitude range. In an extreme-amplitude environment, the global attractive chaotic response that appears in the bistable system enhances the efficacy of such a system, demonstrating that chaos can benefit energy collection. This work establishes an excitation-amplitude-dependent selection principle for PEH designs and highlights the critical yet overlooked role of initial conditions. The observed fragile BAs and hidden/rare attractors provide new perspectives for enhancing system reliability.

Research on data assimilation for turbulence model constants via airfoil wind tunnel experiments

Yang Junwei, Meng Lingting, Wang Xiangjun, Yang Hua

Accepted Manuscript , doi: 10.1016/j.taml.2025.100639

[Abstract] (81) [PDF 2425KB] (1)

Abstract:
Data assimilation algorithms have been demonstrated to increase the accuracy of predictions in airfoil flow fields. However, slight changes in airfoil geometry and Reynolds number (Re) variations could lead to differences in aerodynamic characteristics and stall behavior, consequently affecting assimilation outcomes. Hence, this research uses the ensemble Kalman filter (EnKF) algorithm. The aerodynamic characteristics of two wind turbine airfoils obtained through wind tunnel experiments were investigated under varying degrees of stall by recalibrating the constants in the (S-A) model. The impacts of the airfoil thickness, Re variation, and Gurney flap installation on the assimilation results were subsequently examined. Verifying the applicability of the constants obtained via data assimilation under varying conditions might offer opportunities to reduce the demand for computational resources. The assimilation results indicate that at a Re on the order of magnitude of 10⁵, the original model tends to delay flow separation as the Re increases. Consequently, the recalibrated constant C_b1 generally decreases with increasing Re. Despite belonging to the same airfoil family, discrepancies in the flow separation behavior predicted by the original model resulted in variations in the recalibrated constants. The constants derived from the thinner airfoil induce premature flow separation in the thicker YA-30 airfoil under stall conditions. When assimilated constants are applied to flow field calculations under analogous stall conditions, constants from another condition may demonstrate an optimization effect and substitute the self-assimilated constants, provided that simulations using default constants for both conditions consistently exhibit an experimental separation trend. However, practical implementation requires caution due to the risk of overadjustment.

Physics- and position-aware GNNs for explosion-induced strain field reconstruction

Wei Xiao, Hao Liu, Lei Zhang

Accepted Manuscript , doi: 10.1016/j.taml.2025.100640

[Abstract] (83) [PDF 1425KB] (1)

Abstract:
High-fidelity strain measurements of plate and shell structures are crucial for elucidating failure mechanisms and deformation evolution. These data provide the basis for quantitative damage detection, design optimization, and structural health monitoring. However, laboratory constraints often preclude the acquisition of high-resolution full-field strains, limiting observations to a sparse set of discrete points. Reconstructing complete strain fields from these sparse measurements has therefore become a pressing challenge, for which few effective solutions exist. Motivated by the spatial correlations exhibited under blast loading, we develop a position- and physics-aware graph neural network (PPA-GNN) to recover transient strain fields in plate structures subjected to explosive impacts. The model employs graph-based message passing to encode both spatial topology and governing physical constraints among sensor nodes, markedly improving reconstruction fidelity. To cope with severe data sparsity in practice, we further devise a curriculum-learning schedule that gradually transitions training from dense to extremely sparse sampling, thereby enhancing robustness. The experimental results indicate that the PPA-GNN achieves an R² value of 0.903 when only eight observation points are used, thereby demonstrating its capability for reliable full-field reconstruction under minimal sensing conditions.

Stress wave propagation and ballistic efficiency in ceramic composite armor: the influence of backplate material properties

Wu Yiding, Lu Wencheng, Yu Yilei, Ma Minghui, Gao Guangfa

Accepted Manuscript , doi: 10.1016/j.taml.2025.100638

[Abstract] (67) [PDF 2922KB] (0)

Abstract:
This study tested the dynamic mechanical properties of seven commonly used backing plate materials and conducted ballistic experiments on their corresponding ceramic composite armor. The distribution of projectile fragments was quantitatively analyzed via the Rosin–Rammler model to assess ballistic outcomes. The results indicated that as the dynamic yield strength of the backing plates increased, the degree of projectile fragmentation increased, whereas the extent of plastic deformation decreased. A model of ceramic composite armor was established to analyze the propagation of one-dimensional stress waves within the armor. Research has shown that when the backing plates are in an elastic state, the intensity of stress waves in the ceramic significantly increases, but in a plastic state, most stress waves dissipate within the backing plates, resulting in weaker stress waves in the ceramic. Numerical simulations further quantified the impact of the plastic modulus of the backing plates on armor performance. Maintaining constant strain energy while increasing the plastic modulus improved the stress state at the ceramic back, shifting from tensile to compressive wave dominance, thus enhancing the overall ballistic resistance of the armor. A high sound speed in the backing plates helps optimize the stress state within the armor, thereby enhancing its ballistic performance.

A pseudo-elastic damage-based model for compressive stress in expanded polystyrene foams

Alejandro E. Rodríguez-Sánchez

Accepted Manuscript , doi: 10.1016/j.taml.2025.100637

[Abstract] (69) [PDF 5066KB] (2)

Abstract:
This work presents the application of a pseudo-elastic model to address the uniaxial compressive stress-strain behavior of expanded polystyrene foams. The model combines an Ogden-based hyperfoam formulation for the loading path of experimental testing with a damage-dependent approach for the unloading. The loading during compression is described using a simplified hyperfoam strain-energy function that effectively captures the nonlinear response of compressible polymer foams. For the unloading path, the model incorporates a scalar damage parameter controlled by three key variables: maximum damage, a damage evolution rate, and a transition parameter. Experimental validation confirms the model’s accuracy in predicting the mechanical response of polystyrene foams, including inelastic phenomena. This precision is supported by coefficient of determination R² values close to unity when comparing the model’s predictions with experimental data. Thus, the proposed model provides a practical tool for analyzing the compressive stress response in polystyrene foams.

A neural operator-based hybrid microscale model for the multiscale simulation of rate-dependent materials

Dhananjeyan Jeyaraj, Hamidreza Eivazi, Jendrik-Alexander Tröger, Stefan Wittek, Stefan Hartmann, Andreas Rausch

Accepted Manuscript , doi: 10.1016/j.taml.2025.100636

[Abstract] (76) [PDF 8677KB] (1)

Abstract:
The behavior of materials is influenced by a wide range of phenomena occurring across various time and length scales. To better understand the impact of microstructure on the macroscopic response, multiscale modeling strategies are essential. Numerical methods, such as the FE²-approach, account for micro-macro interactions to predict the global response in a concurrent manner. However, these methods are computationally intensive because of the repeated evaluations of the discretized microscale. This challenge has led to the integration of deep learning techniques into computational homogenization frameworks to accelerate multiscale simulations. In this work, we employ neural operators to predict microscale physics, resulting in a hybrid model that combines data-driven and physics-based approaches. This allows for physics-guided learning and provides flexibility for different materials and spatial discretizations. We apply this method to time-dependent solid mechanics problems involving viscoelastic material behavior, where the state is represented by internal variables only at the microscale. The constitutive relationships at the microscale are incorporated into the model architecture and the internal variables are computed on the basis of established physical principles. The results for homogenized stresses (< 6% error) show that the approach is computationally efficient (~100×faster).

Predicting Stress and Damage in Carbon Fiber-Reinforced Composites Deformation Process using Composite U-Net Surrogate Model

Chen Zeping, Yacouti Marwa, Shakiba Maryam, Wang Jian-Xun, Luo Tengfei, Varshney Vikas

Accepted Manuscript , doi: 10.1016/j.taml.2025.100634

[Abstract] (112) [PDF 3463KB] (0)

Abstract:
Research HighlightsCarbon fiber-reinforced composites (CFRC) are pivotal in advanced engineering applications due to their exceptional mechanical properties. A deep understanding of CFRC behavior under mechanical loading is essential for optimizing performance in demanding applications such as aerospace structures. While traditional Finite Element Method (FEM) simulations, including advanced techniques like Interface-enriched Generalized FEM (IGFEM), offer valuable insights, they can struggle with computational efficiency. Existing data-driven surrogate models partially address these challenges by predicting propagated damage or stress-strain behavior but fail to comprehensively capture the evolution of stress and damage throughout the entire deformation history, including crack initiation and propagation. This study proposes a novel auto-regressive composite U-Net deep learning model to simultaneously predict stress and damage fields during CFRC deformation. By leveraging the U-Net architecture’s ability to capture spatial features and integrate macro- and micro-scale phenomena, the proposed model overcomes key limitations of prior approaches. The model achieves high accuracy in predicting the evolution of stress and damage distribution within the microstructure of a CFRC under unidirectional strain, offering a speed-up of over 150 times compared to IGFEM.

Trajectory Parameter Identification and Impact Point Prediction for Canard Dual-Spin Projectile Considering Nonlinear Effects

Xinxin Zhao, Jinguang Shi, Zhongyuan Wang

Accepted Manuscript , doi: 10.1016/j.taml.2025.100635

[Abstract] (81) [PDF 2147KB] (0)

Abstract:
Canard dual-spin projectiles typically adjust the forebody roll angle for trajectory correction by analyzing deviations between predicted impact points and target positions. An accurate method for trajectory parameter identification and impact point prediction is crucial for this process. This paper introduces nonlinear factors to couple geometric and aerodynamic nonlinear effects at large angles of attack, analyzes angular motion dynamics before and after control initiation, as well as their influence on center-of-mass motion, thereby establishing an improved modified point-mass trajectory equation for such projectiles. Moreover, by mapping the effects of random disturbances and canard-body interactions to a finite set of primary characteristic parameters and employing periodic averaging to suppress fluctuations caused by rapid period changes of the complex angle of attack after control initiation, a nonlinear trajectory filtering model for both uncontrolled and controlled flights is proposed using the Unscented Kalman Filter (UKF) algorithm, with its performance in parameter identification and impact point prediction systematically evaluated. Numerical results indicate that the improved modified point-mass trajectory equation accurately characterizes the nonlinear effects of canard control disturbances on aerodynamics and trajectory compared to traditional methods, closely matching rigid body trajectories for both uncontrolled and controlled flight, while improving computational efficiency by three orders of magnitude to meet real-time requirements. Furthermore, the filtering model effectively predicts uncontrolled trajectories and significantly reduces the influence of canard control initiation and orientation changes on prediction accuracy during controlled flight, thereby providing a theoretical foundation for studying correction strategies and guidance control methods, particularly for multiple control initiations.

Continuum modeling for layer jamming structures

Shuai Zhang, Jiantao Yao, Shizeng Li, Xinbo Chen

Accepted Manuscript , doi: 10.1016/j.taml.2025.100633

[Abstract] (108) [PDF 1779KB] (0)

Abstract:
HighlightLayer jamming structures (LJS) are a class of variable stiffness structures that are valuable for adaptive and soft robotic systems. However, existing models for LJS often rely on discrete approximations or are tailored to specific configurations, limiting their generalizability and computational efficiency. In this study, we propose a continuum elastoplastic constitutive model for LJS based on the average-field technique. The model captures both the jamming (no interlayer slipping) and slipping states of LJS, enabling analytical expressions for yield criteria, and dissipated energy density. Finite element simulations in Abaqus incorporating periodic boundary conditions were conducted to validate the theoretical model under various deformation scenarios, including uniaxial shear, multi-directional shear, and coupled shear-normal loading. The results demonstrate strong agreement between numerical and theoretical predictions, effectively capturing the nonlinear transitions in stiffness and energy evolution. This continuum framework offers a unified, scalable tool for modeling the mechanical behavior of LJS and supports the design and optimization of stiffness-tunable systems in soft robotics and beyond.

Dynamic mechanical behavior and modified Johnson-Cook constitutive model of 95W-Ni-Fe-Co alloy under different processing conditions

Rui Zhu, Xuan Zhou, Dongsheng Han, Yiding Wu, Wencheng Lu, Guangfa Gao

Accepted Manuscript , doi: 10.1016/j.taml.2025.100632

[Abstract] (107) [PDF 2630KB] (1)

Abstract:
Tungsten heavy alloys (W-Ni-Fe) have become critical materials in defense and aerospace applications due to their high density and superior mechanical properties, yet their constitutive models under dynamic loading remain incomplete. This study systematically investigates the mechanical behavior of a 95W-Ni-Fe-Co alloy fabricated through vacuum sintering, solution treatment, and rotary forging processes via quasi-static and dynamic compression testing. Microstructural characterization reveals that solution treatment significantly refines tungsten grains (30.5 μm vs. 45 μm in as-sintered state) while enhancing W/Co diffusion in the binder phase. Rotary forging introduces 20% plastic deformation, achieving 81% yield strength enhancement (1305 MPa vs. 720 MPa in as-sintered condition). Dynamic tests (1500 s^-1-6500 s^-1) demonstrate distinct strain rate strengthening effects: solution-treated alloy exhibits optimal strain hardening capacity (B=1693 MPa) with homogeneous deformation, whereas rotary-forged specimens show higher susceptibility to adiabatic shear instability due to localized deformation band initiation. A modified Johnson-Cook (MJC) model incorporating strain-strain rate coupling coefficients (C₁-C₅) reduces prediction errors to 2.3% (compared with 10%-30% errors from original JC model). Numerical simulations implemented through ABAQUS/VUMAT secondary development validate MJC model accuracy under high strain rates. These findings provide critical theoretical foundations and constitutive model support for tungsten alloy design under extreme service conditions, with future research focusing on fracture criteria and impact behavior investigation.

Numerical simulation of multi-gasbag propulsion system and attitude control of release unit based on two-phase flow method

Xinggan Lu, Shenshen Cheng, Xiaoting Cui, Kun Jiang, Hao Wang

Accepted Manuscript , doi: 10.1016/j.taml.2025.100630

[Abstract] (106) [PDF 1547KB] (0)

Abstract:
Collaborative technology for the remote, large-scale deployment of drones using dispersal systems holds significant potential in applications such as post-disaster rescue, which must balance low overload with high thrust, in addition to precisely controlling the separation attitude. To address these issues, this paper introduces a multi-gasbag propulsion system with a high aspect ratio that coordinates multiple gasbags to generate sufficient thrust. By adjusting the inlet size of the gasbag, the separation behavior of the release unit can be accurately controlled. A multidimensional two-phase flow model is established, accompanied by both combustion and flow experiments and a double-gasbag propulsion experiment. The results demonstrate that the proposed mathematical model is accurate, effectively captures the pressure fluctuations and spatiotemporal distribution of flow field parameters, and determines the separation attitude of the release unit. For the cases studied in this paper, the pressure at the gasbag inlet (z = 650 mm) is the dominant factor during the gasbag propulsion response, causing the release unit to rotate counterclockwise when the gasbag inlet sizes are identical. Increasing the inlet size at z = 50 mm compensates for the adverse effects of uneven axial pressure distribution, thereby achieving a neutral separation for the release unit. When the radii r₁ and r₂ vary between 2 and 12 mm, the angular velocity and attitude angle of the release unit are found to range from -15.50 to 15.20 rad·s^-1 and from -0.109 to 0.106 rad, respectively.

Artificial intelligence application in multiscale biomechanics

Erqian Xu, Jin Zhou, Yan Zhang, Qing Luo, Guanbin Song, Shouqin Lü, Mian Long

Accepted Manuscript , doi: 10.1016/j.taml.2025.100629

[Abstract] (148) [PDF 1776KB] (2)

Abstract:
HighlightThe rapid development and widespread application of artificial intelligence (AI) technology have significantly improved understanding across various fields, including biomechanics. To deepen the understanding of AI applications in this field and explore future developments, this review focuses on the progress of AI in multiscale biomechanics. We first outline the progress history, fundamental principles, and typical models of AI. Next, we introduce the main applications of the two typical AI paradigms—data-driven and knowledge-driven—in the context of multiscale biomechanical studies. The first paradigm focuses primarily on predicting protein structure, interactions, and conformational dynamics at the molecular level, as well as on subcellular structure recognition, cell mechanics prediction and cell trajectory tracking at the cellular level. The second paradigm concentrates on biological fluid and solid mechanics at the tissue level. Finally, the existing issues and challenges faced by current AI technologies in biomechanics are discussed, and potential future issues are proposed from the perspective of informative integration.

Non-equilibrium evaporation of Lennard-Jones fluids: Enskog-Vlasov Equation and Hertz-Knudsen model

Shaokang Li, Livio Gibelli, Yonghao Zhang

Accepted Manuscript , doi: 10.1016/j.taml.2025.100628

[Abstract] (158) [PDF 3097KB] (2)

Abstract:
Enskog-Vlasov equation is currently the most sophisticated kinetic model for describing non-equilibrium evaporative flows. While it enables more efficient simulations than the molecular dynamics (MD) methods, its accuracy in reproducing the flow properties of real fluids is limited by both the assumptions underlying the Vlasov forcing term and the approximation introduced by the Enskog collision term for short-range molecular interactions. To address this limitation, this work proposes a molecular kinetic model specifically designed for real fluids, with the Lennard-Jones fluids as an example. The model is first applied to evaluate the equilibrium characteristics of a liquid-vapour system, including the liquid-vapour coexistence curve, transport coefficients, vapour pressure, and surface tension coefficient. The results show excellent agreement with the MD simulation and experimental data. Furthermore, the model is used to investigate non-equilibrium evaporation, with a particular focus on the velocity distribution function adjacent to the liquid-vapour interface. The results confirm that deviations from the Maxwellian distribution persist in the vapour region, indicating limitations of the classical Hertz–Knudsen relation under pronounced non-equilibrium conditions. This work represents a critical step towards the development of an accurate and efficient computational framework for modelling non-equilibrium liquid-vapour flows for real fluids, with direct relevance to practical applications such as flow cooling.

Electromechanical models for the critical current degradation behavior of coated conductors wound on round cores

Liangyu Wei, Cong Liu, Yihao Li, Jun Zhou, Xingyi Zhang

Accepted Manuscript , doi: 10.1016/j.taml.2025.100627

[Abstract] (137) [PDF 2518KB] (0)

Abstract:
REBa₂Cu₃O_7-_x (REBCO, RE: rare earth elements, such as Y and Gd, etc.) coated conductors (CCs) have been well commercialized. Conductor on round core (CORC) cables have been developed for transporting large direct current (DC) or alternating current (AC) currents over long distances. In this work, electromechanical models for CCs in a CORC structure were established, in which the effects of bending and deflection strains in the REBCO layer of a CC on the structural integrity and critical current density degradation during winding were considered. Compared with the previous model, which considers only the bending strain, the newly presented model agrees better with the experimental results, demonstrating that high winding angles and small diameters of round cores potentially result in severe degradation of the critical current. For the case of AC loss, the experimental results show that high winding angles increase AC loss, whereas the diameters of the former cores have little influence. The revised Norris model gives precise predictions for the applied AC currents close to the critical current but underestimates the losses for applied AC currents less than the critical current, especially for CCs that are wound at high angles. The established electromechanical models are expected to be beneficial for understanding the properties and optimizing the applications of CORC cables.

A three-dimensional statistical damage model for rock-like materials based on principal stress action

Jun Xu, Sen Luo, Shihe Sun

Accepted Manuscript , doi: 10.1016/j.taml.2025.100625

[Abstract] (200) [PDF 1879KB] (4)

Abstract:
Principal stress plays a critical role in the deformation and failure process of rock or rock-like materials. However, existing studies indicate that the construction of a damage model based on principal stresses for describing the entire process of three-dimensional rock fracturing is subject to certain limitations and inadequacies. In this study, an innovative three-dimensional statistical damage constitutive model is developed by integrating the principal stress effect with the Gamma distribution function. This model effectively captures the complete damage evolution process of rock materials with initial defects through the introduction of a compaction correction coefficient and a residual strength correction term. Notably, the simulation accuracy is significantly enhanced in both the initial compaction stage and the post-peak residual strength stage. The parameter θ serves as an indicator of the material brittle-to-ductile transition, whereas the parameter k reflects the material’s strength characteristics. The parameter calibration process consists of three steps: determining the θ value on the basis of the rock brittleness index, deriving the k parameter from the k value growth curve, and finally establishing the peak-residual strength prediction equation under given confining pressure conditions. Compared with the traditional statistical damage model based on the Weibull distribution, this model not only features clear physical significance and a simplified calculation procedure but also contributes to the advancement of the three-dimensional damage fracture theory system for rock mechanics. Moreover, it offers a robust framework for evaluating the mechanical response of rocks under varying confining pressures, which has significant implications for safe design and risk assessment in civil engineering or rock engineering.

A data-driven flight optimization of two-segment flapping-wing aircraft based on Deep Learning

Chi Gan, Song Chen, Zhouteng Ye, Guanxin Hong

Accepted Manuscript , doi: 10.1016/j.taml.2025.100624

[Abstract] (234) [PDF 10998KB] (2)

Abstract:
Flapping-wing aircraft, as a typical example of bionic aviation vehicles, hold significant importance in fields such as environmental monitoring, reconnaissance, and aerobiology research. However, the design of flapping-wing aircrafts usually relies on the imitation of birds or insects in nature and requires extensive iterative optimization. In this study, a computational fluid dynamics (CFD) data-driven flight optimization approach is developed for flapping-wing aircraft design. First, we conduct a bionic aerodynamic analysis of the unsteady flow field during the flapping motions and multiple cases with different combinations of flight parameters are simulated via CFD to investigate the factors influencing the flight performance. The simulation data are subsequently used to establish a deep neural network (DNN) model to explore the relationship between the flapping motions and the flight performance. Finally, optimization algorithms are applied to search for the optimal flight parameter combinations under different weights, which can provide a valuable reference for the overall design and flight optimization of flapping-wing aircraft.

Design of a High-Speed, Low-Turbulence Water Flume with Initial Application to Free Surface Turbulent Wake Flow

David Butler, Skinder Dar, Minh Nguyen, Cong Wang

Accepted Manuscript , doi: 10.1016/j.taml.2025.100621

[Abstract] (211) [PDF 7030KB] (0)

Abstract:
Despite the substantial progress of numerical methods in fluid mechanics, the complex multi-scale, multi-phase nature of turbulent flows continues to necessitate high-fidelity experimental data. As such, the development of a free-surface water tunnel (i.e. flume) capable of delivering high-speed, low-turbulence, free-surface flows is essential for fundamental research for marine applications. We report the design specifications and performance of a water flume recently constructed at the University of Iowa. The flume delivers high-speed (1.6 m/s), low-turbulence (<1.6%) uniform flows in an 8 m test section. The superior performance in delivering and maintaining well-conditioned flows over an extended test section is due to the properly designed upstream and downstream diffusers and the flow conditioners within. An additional high volumetric rate fluorescent dye visualization system was developed and employed for applications that challenge advanced laser-based measurement, particularly near the free-surface. The capability of the flume and associated instrumentation are demonstrated through an on-going investigation of the turbulent wake flow behind a surface-piercing 2D triangular wedge, revealing near free-surface coherent structures such as delayed vortex shedding and vortex-coupled, air-entrained tubes at high Froude numbers. The reported design details, in particular, the extended test section and downstream diffuser, will guide researchers developing similar hydrodynamic facilities for fundamental research.

turbulence.ai: an end-to-end AI Scientist for fluid mechanics

Jingsen Feng(冯晶森), Yupeng Qi(亓宇鹏), Ran Xu(徐冉), Sandeep Pandey, Xu Chu(初旭)

Accepted Manuscript , doi: 10.1016/j.taml.2025.100620

[Abstract] (379) [PDF 1281KB] (2)

Abstract:
Fluid mechanics holds an almost infinite range of unsolved questions whose answers could improve energy efficiency, environmental protection and public health. Yet progress is throttled by scarce resources—human expertise, time cost and research funding. We introduce turbulence.ai, the first fully autonomous AI scientist for fluid mechanics, designed to lift those constraints. A multi-agent architecture unifies hypothesis generation, CFD execution and draft writing. From a single natural-language query the platform (i) formulates testable ideas, (ii) orchestrates a series of numerical experiments, (iii) interprets results and (iv) produces a draft (attached). This advance inaugurates a new chapter in fluid-mechanics research and could expand human’s knowledge base by orders of magnitude.

Large eddy simulations of hypersonic boundary layer transition on a HyTRV model with upstream wall blowing/suction

Xuecheng Sun, Changping Yu, Xinliang Li, Chuanhong Zhang

Accepted Manuscript , doi: 10.1016/j.taml.2025.100619

[Abstract] (206) [PDF 2324KB] (8)

Abstract:
To investigate the effect of wall blowing/suction on hypersonic boundary layer transition, large eddy simulation (LES) is employed to analyze the HyTRV model under an incoming flow with a Mach number of 6 and a unit Reynolds number of 10⁷ m^-1. The model has a length of 1,600 mm, and wall blowing/suction is applied to the windward surface’s upstream region (450-750 mm from the leading edge). The computational results indicate that upstream blowing accelerates the destabilization and breakdown of the streamwise vortex, promotes earlier transitions in the windward vortex region, and enhances the turbulent fluctuation intensity in the outer boundary layer. Conversely, upstream suction delays the transition and suppresses turbulent fluctuations in the outer boundary layer zone. The pressure fluctuation spectra are analyzed at different streamwise positions. The results demonstrate that upstream blowing significantly amplifies the development of a disturbance wave with a frequency of approximately 33 kHz at x = 1100 mm on the windward side. This frequency is hypothesized to correspond to the streamwise vortex instability mode. In contrast, upstream suction markedly suppresses the preexisting spectral peak near 38 kHz. Spectral proper orthogonal decomposition (SPOD) is applied to the streamwise/wall-normal temperature field. The results revealed that upstream blowing substantially increases the energy contribution of the first SPOD mode at a characteristic frequency of 32.55 kHz.

Direct numerical simulation of the effect of wall-generated positive/negative Reynolds shear stress on wall friction resistance in turbulent boundary layers

Qian-Jin Xia, Hongsheng Zhang, Long Lian, Yuan Xue

Accepted Manuscript , doi: 10.1016/j.taml.2025.100611

[Abstract] (294) [PDF 1827KB] (4)

Abstract:
Direct numerical simulation of spatially developing turbulent boundary layers with periodic blowing or suction through a series of inclined slots in a control region was conducted. The wall-generated Reynolds shear stress (RSS), i.e., the RSS on the wall in the control region, is generated through the control scheme. The effect of the wall-generated RSS on friction drag was examined via a series of simulations. The Reynolds numbers of the turbulent boundary layers investigated vary from 300-860 on the basis of the external flow velocity and the momentum thickness. The proposed control scheme was used to verify the relationship between the wall-generated RSS and skin friction drag, and it was found that a wall-generated negative RSS (net positive) increases the skin friction drag, whereas a wall-generated positive RSS (net negative) reduces it. The proposed control method can provide a high drag reduction rate, and even negative resistance and backflow can be observed.

HybridNDiff-UQ: Uncertainty Quantification for Hybrid Neural Differentiable Modeling

Deepak Akhare, Tengfei Luo, Jian-Xun Wang

Accepted Manuscript , doi: 10.1016/j.taml.2025.100609

[Abstract] (255) [PDF 23186KB] (0)

Abstract:
The hybrid neural differentiable models mark a significant advancement in the field of scientific machine learning. These models, integrating numerical representations of known physics into deep neural networks, offer enhanced predictive capabilities and show great potential for data-driven modeling of complex physical systems. However, a critical and yet unaddressed challenge lies in the quantification of inherent uncertainties stemming from multiple sources. Addressing this gap, we introduce a novel method, uncertainty quantification for hybrid neural differentiable modeling, for effective and efficient uncertainty propagation and estimation in hybrid neural differentiable models, leveraging the strengths of deep ensemble Bayesian learning and nonlinear transformations. Specifically, our approach effectively discerns and quantifies both aleatoric uncertainties, arising from data noise, and epistemic uncertainties, resulting from model-form discrepancies and data sparsity. This is achieved within a Bayesian model averaging framework, where aleatoric uncertainties are modeled through hybrid neural models. The unscented transformation plays a pivotal role in enabling the flow of these uncertainties through the nonlinear functions within the hybrid model. In contrast, epistemic uncertainties are estimated using an ensemble of stochastic gradient descent trajectories. This approach offers a practical approximation to the posterior distribution of both the network parameters and the physical parameters. Notably, our framework is designed for simplicity in implementation and high scalability, making it suitable for parallel computing environments. The merits of the proposed method have been demonstrated through problems governed by both ordinary and partial differentiable equations.

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Computational study on the fluid-structure interaction between explosion-induced bubbles and submarine pipes

Lei Gao, Junjie Zhao, Maoyu Qi, Wentao Ma, Shunxiang Cao

Theoretical and Applied Mechanics Letters 15 (2025) 100608. doi: 10.1016/j.taml.2025.100608

[Abstract] (377) [PDF 4312KB] (11)

Abstract:
Submarine pipelines are critical infrastructures for offshore energy transport and communications. Understanding their structural response to near-field explosions is crucial for enhancing their blast resistance and operational safety. This study presents a computational study on the interaction between explosion-induced bubbles and a seabed-mounted pipeline. A recently developed computational framework is employed, which couples a compressible fluid solver with a finite element structural solver via a partitioned procedure. An embedded boundary method and a level-set method are employed to handle the fluid-structure and gas-liquid interfaces. Using this framework, we analyze the flow field evolution, bubble dynamics, and transient pipe deformation. Two distinct response modes are identified: periodic oscillation under low-pressure loading and downward collapse triggered by high-pressure loading and bubble jet impact. Specifically, under high-pressure conditions, the pipe initially deforms inward, generating a localized high-pressure zone within the concave region. During structural rebound, the trapped fluid is expelled upward, giving rise to a bubble jet. Further parametric studies on the pipe’s internal pressure, wall thickness, and support angle reveal several key insights. A higher internal pressure delays structural collapse, and a greater pipe thickness results in more uniform implosion morphologies. The support angle strongly influences the collapse dynamics, with the shortest collapse time occurring at . These findings offer new insights for the protective design of submarine pipelines.

Mechanical behaviors of filopodia protrusion-driven cell fusion

Chaohui Jiang, Zhou Fang, Guangsong Xie, Mei Yang, Dechang Li, Baohua Ji

Theoretical and Applied Mechanics Letters 15 (2025) 100613. doi: 10.1016/j.taml.2025.100613

[Abstract] (339) [PDF 3776KB] (5)

Abstract:
Cell fusion is a basic biological process that plays critical roles in both physiological and pathological processes. However, how mechanical factors influence the fusion process is not fully understood. In this study, we reported filopodia-mediated fusion among MCF-7 cells. We showed that the filopodia protrusion force induced significant bending of the cell membrane, which was essential for membrane fusion between neighboring cells, and then eventually induced the formation of multinucleated syncytia. The inhibition of actin polymerization significantly reduced the fusion ratio, whereas increased actin polymerization promoted fusion. We found that several factors influence the fusion process, e.g., the cell density, substrate pattern, and stiffness. For example, cell density has a significant effect on cell fusion. There was an optimal cell density for cell fusion. The fusion probability increased with increasing cell density within a moderate cell density range but decreased within a high cell density range. Substrate properties also influence the fusion behavior. For example, the fusion ratio was reduced on nanogrooved surfaces and soft substrates because the surface pattern restricted cell alignment and motility, and soft substrates reduced the activity of the actin dynamics of filopodia for cell fusion. This study not only contributes to our understanding of the basic biology of cell fusion but also has important implications for understanding the mechanisms of cancer progression and potential therapeutic intervention methods.

Randomly adjustable stacked open thin-shell cells mechanical metamaterials

Xiaolin Guo, Bohua Sun

Theoretical and Applied Mechanics Letters 15 (2025) 100614. doi: 10.1016/j.taml.2025.100614

[Abstract] (214) [PDF 7497KB] (1)

Abstract:
Open thin-shell structures exhibit advantages such as lightweight properties and high energy absorption efficiency. By randomly stacking these structures as unit cells, adjustable mechanical metamaterials with tunable and stable mechanical properties can be constructed. This study investigates the mechanical performance of randomly stacked open thin-shell mechanical metamaterials using a combined experimental and numerical simulation approach. Results indicate that under compressive loading, shell unit cells primarily dissipate energy through large deformation, snap-fit behavior, friction, and shell relocation. Different combinations of randomly stacked mechanical metamaterials demonstrate nearly identical energy dissipation ratios during the first compression-unloading cycle, indicating that the energy dissipation efficiency exhibits robust stability independent of contact and geometric randomness. However, under limit cycle conditions, increasing the proportion of Type II shells enhances the maximum relative displacement, energy dissipation capacity, and energy dissipation ratio by up to fivefold. Notably, under compressive loading, Type I shells engaged through snap-fit behavior exhibit irreversible deformation after unloading, while Type II shells maintain their configuration without active engagement. The proportion of Type II shells directly determines the mechanical performance of the structure.This research provides new references for the development of lightweight mechanical metamaterials, disordered mechanical metamaterials, and adjustable mechanical metamaterials.

Examining eddy viscosity based LES analyses using low to moderate Reynolds number free stream turbulence due to anisotropic forcing

Hiroki Suzuki, Shinsuke Mochizuki, Toshinori Kouchi

Theoretical and Applied Mechanics Letters 15 (2025) 100615. doi: 10.1016/j.taml.2025.100615

[Abstract] (208) [PDF 3692KB] (2)

Abstract:
This study evaluates the accuracy of large-eddy simulation (LES) analyses using a commonly used subgrid-scale (SGS) model based on the eddy viscosity hypothesis. The evaluation is performed by examining the Reynolds number dependence of turbulence maintained by anisotropic and isotropic forcing techniques derived from Taylor analytical solutions. The Smagorinsky model, the Vreman model, and the coherent structure model are used as SGS models. LES outcomes were evaluated against those produced by direct numerical simulation (DNS). In contrast to the results with isotropic forcing, the turbulent kinetic energy of anisotropic forcing-induced turbulence, as calculated by DNS, exhibits a minimum in the intermediate Reynolds number range. However, all three LES analyses fail to reproduce this minimum and instead show overestimated values. This discrepancy is attributed to reduced spatial inhomogeneity of the turbulent diffusion, pressure diffusion, and pressure-strain correlation terms in the transport equations of the velocity fluctuation intensities in this Reynolds number range. Visualization results for the LES and DNS analyses further show that within this range, LES analyses reproduce two-dimensional tubular flow structures that are not observed in DNS results.

A variationally consistent nodal integration for cubic serendipity finite elements with optimal convergence in explicit transient heat conduction analysis

Songyang Hou, Zhiwei Lin, Zhenyu Wu, Dongdong Wang

Theoretical and Applied Mechanics Letters 15 (2025) 100616. doi: 10.1016/j.taml.2025.100616

[Abstract] (271) [PDF 4116KB] (2)

Abstract:
The 13-node quadrilateral and 39-node hexahedral cubic serendipity elements produce nodally integrated positive-definite lumped heat capacity matrices in higher-order finite element analysis. However, these elements display severe convergence deterioration in explicit transient heat conduction analysis with lumped heat capacity matrices. This convergence decay is due to the violation of variational integration consistency by the standard Galerkin formulation with lumped heat capacity matrices. This issue is resolved by introducing the boundary-enhanced Galerkin weak form that incorporates the elemental boundary contribution in the discrete finite element formulation. Subsequently, it is theoretically proven that a direct nodal integration identically fulfills the variational integration consistency in the context of the boundary-enhanced Galerkin weak form. The proposed variationally consistent nodal integration therefore enables optimal convergence for explicit transient heat conduction analysis with lumped heat capacity matrices. The efficacy of the proposed variationally consistent nodal integration formulation for the 13-node quadrilateral and 39-node hexahedral cubic elements is thoroughly demonstrated via numerical examples.

Numerical simulation study of hypersonic MHD control at mid-low altitudes

Yongchun Yan, Juan Ma, Mingsong Ding, Jianqiang Chen

Theoretical and Applied Mechanics Letters 15 (2025) 100617. doi: 10.1016/j.taml.2025.100617

[Abstract] (220) [PDF 3034KB] (2)

Abstract:
Hypersonic magnetohydrodynamic (MHD) control effectively enhances the aerothermal environment of aerospace vehicles, demonstrating considerable potential in plasma flow regulation and aerodynamic optimization. As aerospace vehicles progress toward mid-low-altitude hypersonic regimes, their external aerothermal conditions become increasingly severe. This study addresses the challenges of complex aerodynamic force/heat environments and the difficulties in MHD control numerical simulations for hypersonic vehicles at mid-low altitudes. On the basis of the perfect gas model and the low magnetic Reynolds number assumption, we conduct numerical simulations of MHD control under mid-low altitudes, high-Mach-number conditions. The findings reveal the following: (1) the low magnetic Reynolds number assumption is valid and computationally accurate, as corroborated by a comparative analysis with the literature; (2) in the mid-low altitude hypersonic regime, magnetic fields significantly suppress the shock standoff distance and reduce the surface heat flux. Both the magnetically controlled shock wave and the thermal protection exhibit nonlinear variations with the Mach number, increasing and then decreasing as the Mach number increases. The optimal Mach number for shock wave control is 13, whereas optimal thermal protection is achieved at Mach 15. At an altitude of 40 km, the optimal magnetohydrodynamic Mach range spans 13–17, achieving a maximum heat flux attenuation of 28.81%. Additionally, the effects of magnetic shock wave control correlate approximately exponentially with altitude within certain parameters, whereas the efficacy of thermal protection behaves linearly with altitude variations.

A status quo investigation of large-language models for cost-effective computational fluid dynamics automation with OpenFOAMGPT

Wenkang Wang, Ran Xu, Jingsen Feng, Qingfu Zhang, Sandeep Pandey, Xu Chu

Theoretical and Applied Mechanics Letters 15 (2025) 100623. doi: 10.1016/j.taml.2025.100623

[Abstract] (247) [PDF 787KB] (1)

Abstract:
We evaluated the performance of OpenFOAMGPT (GPT for generative pretrained transformers), which includes rating multiple large-language models. Some of the present models efficiently manage different computational fluid dynamics (CFD) tasks, such as adjusting boundary conditions, turbulence models, and solver configurations, although their token cost and stability vary. Locally deployed smaller models such as the QwQ-32B (Q4 KM quantized model) struggled with generating valid solver files for complex processes. Zero-shot prompts commonly fail in simulations with intricate settings, even for large models. Challenges with boundary conditions and solver keywords stress the need for expert supervision, indicating that further development is needed to fully automate specialized CFD simulations.

Research Article

Computational method for analytical solution with finite elements (CMAS-FE): Deriving approximate analytical solution for an isotropic homogeneous elastic medium with linear finite element method

Jiajia Yue, Zifeng Yuan

Theoretical and Applied Mechanics Letters 15 (2025) 100618. doi: 10.1016/j.taml.2025.100618

[Abstract] (178) [PDF 5084KB] (3)

Abstract:
This study presents a novel methodology to obtain an approximate analytical solution for an isotropic homogeneous elastic medium with displacement and traction boundary conditions. The solution is derived through solving a specific numerical problem under the scope of the linear finite element method (LFEM), so the method is termed computational method for analytical solutions with finite elements (CMAS-FE). The primary objective of the CMAS-FE is to construct analytical expressions for displacements and reaction forces at nodes, as well as for strains and stresses at elemental quadrature points, all of which are formulated as infinite series solutions of various orders of Poisson’s ratios. Like the conventional LFEM, the CMAS-FE forms global sparse linear equations, but the Young’s modulus and Poisson’s ratio remain variables (or symbols). By employing a direct inverse method to solve these symbolic linear systems, an analytical expression of the displacement field can be constructed. The CMAS-FE is validated via patch and bending tests, which demonstrate convergence with mesh and term refinement. Furthermore, the CMAS-FE is applied to obtain the bending stiffness of a beam structure and to estimate an approximate stress intensity factor for a straight crack within a square-shaped plate.

Harnessing the mechanical properties of Gelatin methacryloyl hydrogels through cooling-induced entanglement

Kerong Wu, Wei Jian, Zhongwei Meng, Kailei Xu, Ji Lin

Theoretical and Applied Mechanics Letters 15 (2025) 100622. doi: 10.1016/j.taml.2025.100622

[Abstract] (171) [PDF 3510KB] (1)

Abstract:
Enhancing gelatin methacryloyl (GelMA) hydrogel mechanics without compromising biocompatibility remains challenging, as conventional chemical crosslinking often disrupts degradation behavior. A cooling-induced entanglement strategy effectively improves mechanical performance while preserving biological properties; however, its underlying mechanisms remain unclear. This study demonstrates that extended cooling durations significantly enhance the mechanical properties of GelMA hydrogels. Microstructural analyses reveal cooling-induced formation of compact polymer networks with reduced mesh sizes. Molecular dynamics (MD) simulations confirm that the cooling process promotes topological entanglements that govern mechanical reinforcement. Guided by these insights, we propose a theoretical model to predict the stress responses of GelMA hydrogels under various cooling durations, establishing quantitative correlations between entanglement mechanisms and mechanical outcomes. This study provides a fundamental understanding of the interplay between cooling conditions, microstructure, and mechanical performance, offering a robust framework for designing GelMA hydrogels with optimized mechanical properties for advanced biomedical applications.

Corrigendum

Corrigendum to “Deep transfer learning for three-dimensional aerodynamic pressure prediction under data scarcity” [Theor. App. Mech. Lett. 15 (2025) 100571]

Hao Zhang, Yang Shen, Wei Huang, Zan Xie, Yao-bin Niu

Theoretical and Applied Mechanics Letters 15 (2025) 100626. doi: 10.1016/j.taml.2025.100626

[Abstract] (146) [PDF 206KB] (0)

Abstract:
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Investigation on Savonius turbine technology as harvesting instrument of non-fossil energy: Technical development and potential implementation

Aditya Rio Prabowo, Dandun Mahesa Prabowoputra

2020, 10(4): 262-269 doi: 10.1016/j.taml.2020.01.034

[Abstract](3271) [FullText HTML](1688) [PDF 3192KB](149)

Crack propagation simulation in brittle elastic materials by a phase field method

Xingxue Lu, Cheng Li, Ying Tie, Yuliang Hou, Chuanzeng Zhang