With the increasing deployment of additively manufactured Ti-6Al-4V in aerospace and other high-performance structural applications, reliable prediction of fatigue life under complex multiaxial loading has become essential for safe design and lifecycle management. However, conventional data-driven approaches often lack predictive accuracy and physical consistency on small datasets and non-proportional multiaxial stress states, limiting their generalizability and interpretability. To address these limitations, this work computes the Mises equivalent stress directly from experimental loading histories and incorporates a Basquin-model-based theoretical fatigue life as prior physics knowledge. Building on this prior, we propose a residual connection-based physics-informed neural network (PI-Res) that learns only the datadriven residual relative to the theoretical life, thereby merging mechanistic fidelity with statistical adaptability. Using laser powder bed fusion (L-PBF) Ti-6Al-4V as the case material, we conduct a systematic comparison against representative purely data-driven baselines—artificial neural networks, random forests, and support vector regression—as well as three canonical data-physics fusion strategies: physics-informed feature engineering, physics-informed loss functions, and physics-informed residual connections. Across multiaxial loading scenarios and distinct life regimes, the PI-Res framework consistently demonstrates superior predictive accuracy alongside stronger adherence to physical trends implied by the stress-life relationship. Moreover, by anchoring the learning process to a mechanistic prior and delegating only the unexplained variance to the network, PI-Res improves robustness under data scarcity and enhances interpretability of model behavior. These findings indicate that residual-style injection of domain knowledge offers a principled pathway to reconcile small-sample constraints with mechanistic coherence in fatigue modeling. Practically, the proposed approach provides a reliable tool to support fatigue life assessment, design margins, and maintenance scheduling for additively manufactured components. Theoretically, it illustrates a transferable physics-data fusion paradigm that can be extended to other material systems and generalized multiaxial fatigue problems where integrating prior physics with flexible learners is crucial.

A novel method combing finite element analysis and a stress function is presented to determine the complete singular stress field in angularly heterogeneous material V-notched structure. This is motivated by the challenge of calculating the stress field, which initiates cracks and structural failure. First, stress singularity orders are obtained through singularity characteristic analysis. Then, the governing and the compatibility equations for the angularly heterogeneous material are transformed into ordinary differential equations using a stress function based on the Williams asymptotic expansion. Solving these yields the stress function expression. Subsequently, coefficients in the asymptotic expansion are determined from finite element stress results, reconstructing the asymptotic stress field near the notch tip. The effects of the number of finite element nodes, characteristic distance, and truncation terms on stress intensity factor calculations are examined. Results show the stress intensity factor stabilizes with an increasing number of finite element nodes, indicating the selection of these nodes does not affect result stability. Stress intensity factors change with characteristic distance when the number of truncation terms is small, but stabilize as the number of truncated terms approaches five or six.

Composite materials exhibit diverse microstructure distributions, with periodic microstructures being a typical pattern. Periodic structures feature repeating basic cells, representing the situation where the inclusion arrangement within a material changes from completely disordered to strictly ordered. Modern composite material design, especially computer-aided material design, usually refers to the design of periodically distributed cells. Multi-coating refers to a new type of coating in which the geometric parameters are proportional on the thickness coordinate. Multi-coating can achieve gradient changes in material parameters, allowing for gradient changes in the mechanical properties of the coating and thereby enabling the design and control of material properties such as strength, toughness, and stiffness. Nanocomposites possess unique mechanical properties. When the structural size of the reinforcing phase reaches the nanoscale, the surface effect cannot be ignored. The macroscopic mechanical properties of nanocomposites are different from those of traditional composites. In this work, based on the unit cell method of micromechanics and the Gurtin-Murdoch theory of surface elasticity, the elastic field and effective property of periodic coated-fiber nanocomposites subjected to longitudinal shear loads are studied. The analytical solution for the longitudinal shear effective modulus of periodic nanocoated composites is obtained using the unit cell functional variational method and the eigenfunction expansion method. The consistency between the obtained solution and the existing results indicates the validity of the proposed method. The macroscopic effective property of periodic nanocomposites can be controlled by changing the microstructure parameters of the multi-coating. The effects of coating mechanical properties, coating geometric parameters, surface properties and fiber volume fraction on the effective properties of the composite are discussed. The analytical method proposed in this paper and the obtained results provide a theoretical basis for the design of periodic nanocoated fiber composites and the regulation of their mechanical properties.

In the field of engineering vibration control, the parameter design of traditional dynamic vibration absorbers typically neglects the damping inherent in the primary system. However, structural damping is unavoidable in practical applications, and disregarding this factor introduces significant errors and diminishes vibration suppression effectiveness. To resolve this limitation and enhance engineering applicability, this study aims to solve the optimization design problem of a negative-stiffness dynamic vibration absorber incorporating an amplification mechanism under the condition of primary system damping. The research first establishes the precise governing differential equations of the system and derives its analytical solution. Given that the presence of primary system damping invalidates the classical fixed-point theory, a numerical optimization approach is employed: the primary system amplitude is normalized and based on the criterion of minimizing the maximum primary system amplitude, optimal parameters including the stiffness ratio and damping ratio are determined through numerical search techniques. The accuracy of the analytical solution is subsequently verified using numerical simulations. The results demonstrate that, compared to traditional dynamic vibration absorber designs ignoring primary system damping, the proposed method significantly improves the overall vibration reduction efficiency of the negative-stiffness dynamic vibration absorber with amplification mechanism and effectively reduces the sensitivity of the primary system's resonant amplitude to variations in excitation frequency. Comparative vibration suppression experiments between the grounded negative-stiffness dynamic vibration absorber with amplification mechanism and conventional dynamic vibration absorbers further validate that the proposed negative-stiffness device exhibits significantly superior performance in both effective bandwidth and vibration reduction depth. This study provides a solid theoretical foundation and a practical optimization methodology for negative-stiffness dynamic vibration absorbers incorporating amplification mechanisms. Its optimization strategy, which explicitly considers primary damping, markedly enhances the practical effectiveness and adaptability of the absorber. Consequently, the proposed negative-stiffness dynamic vibration absorber demonstrates broad application prospects in engineering fields requiring efficient broadband vibration suppression, such as precision instruments, offering a novel solution for high-performance vibration control.

Based on equilibrium thermodynamics and the Gent hyperelastic model, a coupled electromechanical constitutive model is developed for circular dielectric elastomer membrane actuators under combined internal pressure and voltage. This investigation systematically examines the influence of rigid inclusion size on the electromechanical response, addressing a crucial design parameter for enhancing the performance and reliability of such actuators. The study establishes a complete theoretical framework that connects material behavior with geometric configuration, providing a solid foundation for performance prediction and design optimization. To accurately analyze this electromechanical coupling behavior, the governing nonlinear boundary value problem is solved using the shooting method. This numerical approach effectively handles the coupled mechanical and electrical equilibrium equations through an iterative solution procedure that satisfies all boundary conditions. The methodology enables precise determination of the membrane's deformation field, stress distribution, and electric field characteristics under various inclusion sizes and loading conditions, offering reliable numerical predictions for design purposes. The computational results reveal that the inclusion size predominantly influences the mechanical and electrical response at the inner boundary region. Increasing the inclusion size leads to a notable suppression of the large oscillations in vertical displacement, stretch ratio, and true stress that are typically induced by applied voltage. This suppression effect demonstrates how geometric parameters can be utilized to control the dynamic response of the membrane. Further analysis of the electric field distribution demonstrates that larger inclusions effectively stabilize the electric field near the critical inner boundary while simultaneously enhancing its overall spatial uniformity. These combined effects contribute to a significant increase in the critical electric field strength, thereby substantially delaying the onset of electromechanical instability and improving the operational safety of the device. These findings provide valuable theoretical guidance and practical insights for optimizing the design of high-performance dielectric elastomer actuators. Through appropriate selection of inclusion size, more stable actuation performance can be achieved with reduced stress concentration and improved dielectric strength. The research outcomes offer clear design principles for enhancing device reliability in various engineering applications. The established methodology and obtained results contribute to the development of more reliable dielectric elastomer devices with predictable performance characteristics, providing important references for both academic research and engineering practice.

To enhance the energy absorption performance of lightweight thin-walled tubular structures, a lightweight lattice structure was introduced into the end-folded origami tube, resulting in a novel high-energy-absorption composite configuration. Quasi-static axial compression tests and finite element analysis of the composite tube revealed that, during deformation, the outer origami tube guided the deformation of the internal lattice structure. Compared to a stand-alone end-folded origami tube, the incorporation of the internal lattice structure increased the average load-bearing capacity by 14.77%. Furthermore, a parametric study was conducted to investigate the influence of key design factors—including the thickness ratio between the lattice and the tube, the number of longitudinal lattice cells, and the width ratio of the lattice configuration—on the energy absorption performance of the composite tube. The results demonstrated that variations in these parameters significantly affected the composite tube's stiffness, leading to multiple deformation modes, including symmetric deformation, diamond deformation, extensional deformation, and mixed deformation, which in turn caused substantial differences in energy absorption performance. Notably, adjusting the internal lattice thickness and width ratio increased the average load-bearing capacity by up to 30.75%. Finally, a theoretical prediction of the composite tube's average load was performed using the super-folded element method, yielding an error of only 12.1% compared to experimental results. In summary, the proposed lattice-reinforced end-folded origami composite tube not only features simplified manufacturing but also exhibits excellent energy absorption characteristics. Its innovative structural design provides valuable theoretical guidance and engineering insights for the structural optimization and performance enhancement of similar composite tubes.

The mechanical behavior of coarse soil is affected by factors such as relative density, stress level, and loading path, resulting in distinct deformation characteristics, such as dilatancy under low confining pressure and contraction under high confining pressure. This paper develops a hypoplastic model for coarse-grained soil by introducing an asymptotic state boundary surface, which can be used to determine the flow direction of rockfill during shearing. In addition, a new density factor is defined based on the relationship between the current state point and the critical state line in the e-p plane to account for the state-dependent behaviors of coarse-grained soil. Model predictions are compared with the triaxial test data of Type I rockfill from the Changhe Dam to verify the proposed hypoplastic model. Results indicate that an increase in confining pressure reduces the tendency for dilatancy deformation, alongside the occurrence of strain-hardening behavior, as shown in the stress-strain curve under drained loading conditions. Conversely, excess pore water pressure within the specimen decreases as axial strain increases under undrained loading conditions. The proposed model is capable of describing the complex behaviors of coarse-grained soil with a simple formula and serves as a novel technical approach for geotechnical numerical analysis.

Hybrid lattice configurations that incorporate diverse structural units offer a promising pathway to tailor the mechanical performance of hybrid lattice sandwich structures. A deeper understanding of the underlying mechanisms governing how hybridization influences global structural responses is essential for establishing rational design strategies. In response to the requirements of mechanical performance regulation in hybrid structures, this study investigates the influence mechanisms of core-layer unit hybridization on the mechanical performance and deformation characteristics. Based on the specific modulus and yield stress responses of eight representative lattice structure units, four units with significant geometric and mechanical disparities were strategically selected, and ten substitution-type hybrid core configurations were developed through spatial arrangement optimization. The corresponding lattice sandwich structure specimens were fabricated via fused deposition modeling (FDM). Combined with finite element analysis and compressive experiments, the effects of substitution configuration on load-bearing characteristics and deformation modes were revealed. The results demonstrate that the performance difference between the substitution units and the matrix units dominates the deformation mode transition in hybrid structures. Weak-unit substitution in strong matrices induces premature core-layer activation, reducing overall specific modulus and yield stress of the structure by 41.78% and 25.58%, and 45.19% and 26.07%, respectively, compared to their homogeneous counterparts with all hybrid combinations exhibiting similar mechanical performance at equivalent substitution volume fractions. Conversely, strong-unit substitution in weak matrices delays core densification while enhancing load redistribution to the upper and lower layers. The specific modulus demonstrated maximum and average deviations of 10.5% and 4.2%, respectively, while the yield stress exhibited corresponding maximum and average deviations of 14.0% and 6.6%, respectively. The results provide useful references for the design and optimization of hybrid lattice cores. In particular, the findings highlight that the mechanical performance under large-deformation conditions can be enhanced through selective reinforcement strategies, where stronger units are judiciously introduced into critical regions of the core to replace weaker ones. Such a substitution scheme avoids detrimental weakening effects while promoting improved load-bearing capacity and damage tolerance. These insights offer guidance for engineering hybrid sandwich designs capable of meeting specialized demands in extreme service environments.

To address the limitations of existing engineering models for penetration depth that inadequately account for the coupling between the impact-induced energy release reaction of metal-based energetic jets and penetration behavior, a novel engineering model for penetration depth was developed. The model was based on a detailed analysis of the physical process of energetic jet penetration into steel targets, combined with the dynamic features of the impact-induced energy release. The model aimed to improve prediction accuracy for steel targets under impact conditions encountered in shaped charge applications. The quasi-steady theory of ideal incompressible fluid mechanics was adopted to describe fluid-like jet behavior. A jet transient reaction time was introduced as a key parameter to capture the timescale of chemical energy release relative to the penetration event. The model systematically incorporated the staged effects of peak overpressure arrival time and the evolving strength of both jet and target materials. Analytical expressions were derived to link penetration depth with jet properties, jet transient reaction time, and target resistance, providing a quantitative framework for performance prediction. Model parameters were calibrated using experimental measurements. Based on this framework, the influence of jet transient reaction time on penetration depth was investigated. Results show that penetration depth first increases and then decreases as reaction time extends. This nonlinear trend indicates that neither very short nor excessively long reaction time is favorable for maximizing penetration. Experimental validation was performed; results show that model predictions deviate by less than 10% from measured penetration depths under multiple test conditions, confirming the model's accuracy. The proposed model provides new theoretical insight into the coupling between penetration mechanics and impact-induced energy release of metal-based energetic jets. It also offers practical guidance for the structural optimization of shaped charges and supports the quantitative assessment of damage to armored targets, showing potential value for both defense applications and engineering design.

To improve the impact resistance of metal honeycomb structures, three new types of impact protection structures, namely, closed bent honeycomb, concave filled honeycomb, and star-shaped curved honeycomb, were proposed and analyzed via finite element simulations using ANSYS/LS-DYNA. The deformation patterns and energy absorption capacities were evaluated at different impact velocities. Results showed that deformation patterns were related to the cell element structure and impact velocity. The closed bent honeycomb exhibited superior nominal stress and energy absorption efficiency compared to the other structures. Geometric parameters of honeycomb cell elements do not affect the trend of the nominal stress-strain curves. Increasing the bending angle of the closed bent honeycomb increased platform stress and decreased dense strain. Under medium-velocity impact, the platform stress of the 60° closed bent honeycomb structure increased by 19.5% compared to the 45°structure. Increasing relative density significantly improved energy absorption efficiency; the specific energy absorption of the high-density 60°closed bent honeycomb structure increased by 207.6% compared to the low-density structure.