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.

Concrete structures in marine environments will be attacked by corrosive ions in seawater, including chloride ions, sulfate ions, etc. Those ions can significantly cause the degradation of the mechanical properties and durability of concrete. They can also cause problems like reinforcement corrosion, cracking, and spalling, and lead to the decrease of the service life of concrete structures and pose serious threats to structural safety. Investigating the evolution of mechanical properties of concrete under the combined action of sulfate and chloride ions is crucial for designing more durable concrete structures in marine environment. However, there is currently no consensus on the evolution of concrete modulus under such combined corrosion conditions. To address this gap, this paper presents an experimental study on the modulus evolution of concrete under the combined corrosion of sulfate and chloride ions. Concrete samples were prepared and subjected to accelerated corrosion experiments in artificial seawater. Ultrasonic non-destructive testing (NDT) was used to measure the changes in ultrasonic wave velocity in concrete. This allowed us to track the evolution of concrete modulus under corrosion conditions. Based on the experimental results, a mechanical-chemical model was developed. The model integrates the continuous hydration of concrete, the chemical reactions of sulfate ions with concrete, the complexation reactions of chloride ions, and other chemical processes. The model helps explain the competitive mechanism between sulfate and chloride ions during the corrosion process. The results show that the elastic modulus of concrete initially increases due to the filling effect of hydration products and the formation of ettringite and Friedel's salt. However, as the corrosion continues, the excessive filling of pores by expansive products caused by sulfate ions leads to a gradual decrease in modulus. The model successfully captures these changes and fits well with the experimental data. Additionally, it was found that chloride ions react with tricalcium aluminate to form Friedel's salt. This reduces the amount of ettringite formed by sulfate ions, thereby reducing the expansion force and delaying the decline in dynamic elastic modulus. This also reduces the damage caused by the expansion force. The findings provide a theoretical basis for designing concrete structures in marine environments with stronger resistance to sulfate and chloride corrosion. This can help engineers develop more effective strategies to enhance the durability of concrete in marine environments. This, in turn, can extend the service life of marine infrastructure and reduce maintenance costs.

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.

Electrical connectors are critical components in electronic systems, enabling the conduction of electrical current and the transmission of signals. They are extensively used in various fields such as aerospace, telecommunications, computing, and the automotive industry. The reliability and stability of an entire system often depend on the performance of these connectors. Any failure may not only disrupt normal device operation but also result in severe equipment damage. Among known failure mechanisms, contact failure caused by inadequate insertion and extraction force accounts for a significant proportion. To address this issue, a general analytical formula for calculating insertion and extraction force was derived based on a cantilever beam model. This model was used to analyze the mechanical behavior and force variation during the insertion and extraction of the pin and socket components. A comprehensive understanding of the force distribution during these processes was established through this approach. Subsequently, a finite element model was developed for a specific type of electrical connector's contact components. Simulation analyses were conducted to examine how the insertion and extraction force changes with displacement. These simulation results were then validated through controlled experimental tests. The findings indicate that the relative error between the theoretical predictions, simulation outputs, and experimental measurements remains below 8%. The strong agreement among these methods confirms the accuracy and applicability of the developed models. To fulfill practical engineering requirements and avoid excessive mechanical stress, the validated theoretical model was further applied to optimize the design parameters of the connector's contact springs, with a particular focus on their length and thickness. A qualified design range was identified, effectively distinguishing safe and failure regions. This provides clear engineering boundaries for failure-resistant design and enhanced service life. Additionally, the outcomes offer valuable guidance for the structural optimization of contact components in electrical connectors, supporting enhanced performance, stability, and durability in demanding applications.

This study aims to explore the variation law of threaded joints' loosening under transverse vibration and examine the mechanical behavior during the loosening process. Using a single-bolted, single-lap joint structure, a preload degradation model for bolted connections was developed. Friction torque and shear models were established for both the bearing surface and thread surface. The friction-shear model for the bearing surface and the thread surface caused by the additional bending moment was also established. The impacts of vibration amplitude, thread pitch, and initial preload on the variation of bolt preload were analyzed, and the failure mechanism of bolt loosening was explored through case studies. A transverse vibration test bed was designed and fabricated, and the preload decline curves under different parameters were obtained, verifying the rationality of the theoretical model between loosening factors and the preload. The results indicate that when the loosening torque exceeds the combined friction torque of the bolt head's bearing surface and the thread surface, the bolt reaches the critical condition for loosening. The friction torque between the bolt head's bearing surface and the thread pair's surface decreases when the vibration amplitude increases. When the vibration amplitude reaches the critical value, the bolt loosening further accelerates. A higher initial preload makes loosening harder to reach and slows preload decay. Under identical conditions, larger vibration amplitude and thread pitch accelerate preload decline.

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.

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.

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.

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.

Fatigue failure, recognized as one of the most prevalent failure modes in engineering structures, remains inadequately understood in terms of its fundamental mechanical mechanisms. Existing fatigue crack growth models are highly dependent on experimental fatigue data while lacking a universal theoretical framework. To overcome these limitations, we develop a Fatigue-Free Calibration Cohesive Zone Model (F-free model), which can efficiently predict fatigue crack growth rates without the need for fatigue data. Through the definition of cohesive endurance limit and its associated separation displacement, a cyclic damage increment triggering criterion is established. The concept of conditional yield stress in elastoplastic materials is extended to the framework of the cohesive zone model. The cohesive endurance limit is determined as the intersection point between the actual traction-separation curve and a straight line parallel to its initial linear segment. The proposed F-free model is validated by comparing its simulated fatigue crack growth rates with experimental data from two key test scenarios: interlaminar delamination in composite laminates and face-core debonding in sandwich structures. The prediction range of this model can effectively encompass the experimental observation results, accurately capturing both the crack growth rates and the Paris' exponent values for mode I interfacial fatigue cracking. The applicability of the F-free model is further evaluated. The fatigue crack growth rates of interlaminar delamination in double cantilever beam (DCB) specimens under different cohesive endurance limits are simulated. The results indicate that the F-free model can provide a prediction region for interfacial fatigue crack growth rates and a prediction range for the Paris' exponent between 0.99 and 6.3. The proposed F-free model is applicable for predicting the fatigue crack growth of elastoplastic materials or at ductile fracture interfaces. This advancement provides a novel theoretical framework for fatigue damage analysis, effectively bridging the gap between empirical observations and mechanical modeling. The proposed F-free model is able to significantly improve the computational efficiency of fatigue damage tolerance analysis.