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2025 Vol. 46, No. 5
Published: 2025-10-27
571
A data-physics hybrid approach for multiaxial fatigue life prediction of Ti-6Al-4V alloy
With the increasing application of additively manufactured Ti-6Al-4V alloys in aerospace and high-performance structural components, understanding their fatigue behavior under complex loading conditions has become essential. This study proposes a data-physics hybrid fatigue life prediction model that integrates Mises equivalent stress as prior physical information to enhance the modeling of multiaxial fatigue mechanisms. Focusing on L-PBF Ti-6Al-4V material, three representative data-driven methods—artificial neural networks, random forests, and support vector machines—are compared. Furthermore, the effects of different physics-informed strategies, including feature engineering, loss function design, and residual connections, are systematically evaluated. Results show that the proposed physics-informed residual network achieves higher predictive accuracy and improved physical consistency, particularly in low-cycle regimes and under multiaxial loading. The findings offer valuable insights for developing physically reliable fatigue life prediction models for advanced structural materials.
2025 Vol. 46 (5): 571-588 [
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589
Calculation of singular stress near the vertex of angularly heterogeneous material notch by the stress function method
The singular stress field around the notch tip of angularly heterogeneous material will initiate crack and cause structural failure, and its calculation is quite challenging. Here an innovative new method combing the finite element analysis with the stress function is presented to determine the complete singular stress field in the angularly heterogeneous material V-notched structure. Firstly, the stress singularity orders of notches in angular heterogeneous materials are obtained basing on the singularity characteristic analysis. Then, the governing equation and the compatibility equation for angularly heterogeneous material is transformed into the ordinary differential equation by introducing a stress function expressed by the Williams asymptotic expansion. The expression of stress function is obtained by solving the built ordinary differential equation. Furthermore, the coefficients in the stress function asymptotic expansion are determined from the known finite element stress results. Finally, the asymptotic stress field near the notch tip of angularly heterogeneous material is reconstructed. The effects of the selected number of finite element nodes, characteristic distances, and truncation terms on the calculation results of stress intensity factors are respectively examined. The stress intensity factor forms a horizontal line with the number of selected finite element nodes which means that the value remains stable. It shows that the selection of finite element nodes does not affect the stability of the calculational results. When the number of truncation terms is small, the stress intensity factors gradually change with the increase of the characteristic distance. However, when the number of truncated terms is approaching to five to six, the stress intensity factors remain stable with the increase of the characteristic distance.
2025 Vol. 46 (5): 589-597 [
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598
Effective longitudinal shear property of periodic multi-coated nano-fiber composites based on eigenfunction expansion-variational method
The microstructure distribution forms within composite materials are diverse, and periodic microstructure is one of the typical distribution patterns. Periodic structures have basic cells that are repeatedly distributed, 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 of the longitudinal shear effective modulus of periodic nanocoated composites is obtained by 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.
2025 Vol. 46 (5): 598-609 [
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610
Parameter optimization and experimental study of a damped dynamic vibration absorber with negative stiffness
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 both in terms of 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.
2025 Vol. 46 (5): 610-625 [
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626
The influence of inclusion size on the electro-mechanical behavior of circular dielectric elastomer membrane actuators
Based on the thermodynamic theory of equilibrium state and combined with the Gent superelastic material model, this study established a force-electric coupling constitutive model describing the circular dielectric elastomer thin film actuator under the combined action of internal pressure and voltage. Through theoretical analysis and numerical calculation, the influence of inclusion size on the force-electric response behavior of circular films was systematically studied. The numerical simulation results show that the size variation of inclusions mainly affects the inner boundary of the film rather than the outer boundary. More importantly, increasing the size of inclusions can effectively suppress the violent fluctuations of the vertical displacement, tensile ratio and true stress of the film under the action of voltage, and significantly improve the electric field distribution characteristics of the film: on the one hand, it makes the electric field distribution at the inner boundary of the film tend to be stable; on the other hand, it enhances the uniformity of the overall electric field, resulting in a significant increase in the critical electric field strength of the film. This research provides important theoretical basis and technical guidance for the optimal design of high-performance dielectric elastomer film actuators.
2025 Vol. 46 (5): 626-641 [
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642
Energy Absorption Performance of the Origami-ending Tube Based on Grid Enhancement
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 standalone 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.
2025 Vol. 46 (5): 642-654 [
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655
Hypoplastic model for coarse soil with an asymptotic state boundary surface
The mechanical behavior of coarse soil is influenced by various factors, including relative density, stress level, and loading path, all of which exhibit distinct deformation characteristics, such as dilatancy under low confining pressure and contraction under high confining pressure. This paper develops a hypoplastic model for coarse 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 soil. Model predictions are compared to the triaxial test data of Type I rockfill from the Changhe Dam to verify the proposed hypoplastic model. It indicates that the increase in confining pressure will reduce the tendency for dilatancy deformation, alongside the occurrence of strain-hardening behavior evident 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 can describe these behaviors and serves as a novel technical approach for geotechnical numerical analysis.
2025 Vol. 46 (5): 655-666 [
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667
Mechanical properties and deformation mechanisms of lattice sandwich structures with a replaceable hybrid core configuration
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 performances 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 compression experiments, the mechanisms of the substitution configuration on the 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 homogeneous counterparts, with all hybrid combinations exhibiting similar mechanical performances 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%. 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.
2025 Vol. 46 (5): 667-680 [
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681
Study on the Engineering Model of Penetration Depth of Metal-based Energetic Jet Acting on Steel Targets
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 times are favorable for maximizing penetration. Experimental validation was performed; results show that model predictions deviate by less than 10 percent 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.
2025 Vol. 46 (5): 681-692 [
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693
Research on the crashworthiness of new honeycomb structures
In order 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, are proposed. Numerical simulations of the honeycomb impact resistance were carried out using the ANSYS/LS-DYNA finite element method, and the deformation patterns and energy absorption capacities of the three honeycombs were analyzed under different impact velocities. The results show that the deformation patterns of the three honeycomb structures are related to the cellular element structure and impact velocity. The nominal stress and energy absorption efficiency of the closed-bending honeycomb are better than those of the other structures; the geometrical parameters of the honeycomb cell elements do not affect the trend of the nominal stress-strain curves. The larger the bending angle of the closed bend honeycomb, the higher the value of platform stress and the lower the value of dense strain. Under the medium-velocity impact, the platform stress of 60° closed bend honeycomb structure increased by 19.5% compared with that of 45° structure; increasing the relative density can effectively improve the energy absorption efficiency of the honeycomb structure, and the specific energy absorption of the high-density 60° closed-bend honeycomb structure increased by 207.6% compared with that of the low-density.
2025 Vol. 46 (5): 693-706 [
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