Lithium metal is a highly promising anode material due to its high theoretical capacity and low reduction/oxidation potential, and has received extensive attention. However, the formation and growth of lithium dendrites poses the biggest challenge to its commercialization. The use of solid-state electrolyte, instead of liquid electrolyte, has become a potential path to inhibit the growth of lithium dendrites. However, issues such as poor metal-lithium interface contact and low ionic conductivity in solid-state electrolytes persist. Composite solid-state electrolytes, prepared by combining polymers with inorganic ceramic electrolytes, have shown effectiveness in inhibiting the growth of lithium dendrites. Although these composite solid electrolytes typically have high ionic conductivity, their elastic moduli are low. Currently, the mechanism of dendrite suppression by low-modulus composite solid-state electrolytes, especially low-modulus multiphase composite solid-state electrolytes, remains incompletely clarified. Therefore, this paper considers the mechanical effects of solid electrolytes and builds a mechanical-chemical model using the phase field method. By taking poly (ethylene oxide) (PEO)-based composite-state electrolyte as an example, the study investigates the influence of composite solid electrolyte modulus on dendrite growth. The results show that the higher the electrolyte modulus, the greater the stress on the lithium metal, leading to a more uniform distribution of lithium ions on the interface between the electrolyte and the lithium anode electrode. The higher stress also tends to cause the plastic deformation of lithium dendrites, thus inhibiting their growth. This research deepens the understanding of the mechanism of inhibition of lithium dendrites by low-modulus multiphase composite solid electrolytes, and provides guidance for the design of composite solid electrolytes.

To gain a deeper understanding of the constraint effect from double crack tips and accurately characterize it, this study focuses on non-collinear parallel double cracks in a homogeneous plate. It examines the stress and strain fields associated with these double cracks, employing the ABAQUS finite element analysis software. Particular attention is paid to their behaviors at various horizontal distances (s) and vertical distances (h). Additionally, by leveraging the unified constraint parameter A_p, the constraints of double crack tips are compared with those of coalesced single crack tips. The findings reveal significant differences in the distributions and magnitudes of stress and strain at double crack tips compared to coalesced single crack counterparts. The conventional method of calculating the constraints from double cracks based on the stress or strain field at a crack tip, as done for single cracks, would lead to inaccurate results. Comparison of A_total, A_inside, and A_outside with A_single shows that considering both inside and outside crack tip strain fields aligns the variation trend of A_total more closely with A_single, with a remarkably narrow fluctuation. The constraint magnitude for coalesced single cracks ranges from 0.10 to 0.30 of the total strain field (A_total). This approach demonstrates a degree of universality, unaffected by whether the double cracks coalesce or not. It can be directly applied to quantify the constraints imposed by double cracks, regardless of their coalescing status. This study offers valuable insights into the constraint effect of double crack tips and presents a novel method for characterizing the constraints associated with double cracks. In summary, this novel approach offers a more comprehensive and accurate understanding of the complex constraints from double cracks, providing scientific support for evaluating structural integrity with double and multiple cracks.

To improve blast and impact resistance of sandwich structures, this study introduces a composite sandwich structure comprising a re-entrant (RE) negative Poisson's ratio core, polyethylene (PE) fibers, and silicon carbide (SiC) ceramics. Utilizing the coupled Eulerian-Lagrangian (CEL) algorithm within ABAQUS, the dynamic response of this structure under explosive loading was simulated, assessing the impact of various core layer configurations on protective performance through structural deformation mechanisms, velocity response features, and energy absorption capacities. At equivalent areal densities, the incorporation of ceramic and polyethylene layers led to reductions in upper and lower panel deformations by up to 53% and 5.7%, respectively, relative to an RE-only sandwich layer. Notably, a core configuration of SiC-PE-RE optimized interlaminar load distribution, minimizing lower panel deformation; an increase in panel support strength correspondingly reduced panel velocities. Positioning the SiC and PE layers at the upper and middle core layers, respectively, achieved peak reductions in upper and lower panel deformations by 18.84% and 16%, compared to the RE sandwich layer, exhibiting the most rapid rate of decay. Conversely, positioning the RE layer at the upper core resulted in augmented local deformations, leading to localized crushing failures in the PE and SiC layers, thereby maximizing the energy-absorption incrementby up to 14%.

To investigate the impact of surface topography on the mechanical properties of additive manufacturing materials, in this paper, high-strength aluminum alloy specimens were fabricated by the selective laser melting method. The influences of scanning speed, heat treatment, deposition direction, and surface roughness on tensile mechanical properties were examined. The surface topography measured by an optical microscope was reconstructed based on the Fourier series and MATLAB software, and the analytical solution of the stress concentration coefficient of the surface topography was derived using the Airy stress function. Finite element analysis was conducted using ABAQUS software to validate the analytical results. The probability density function of the stress concentration coefficient was obtained through normal fitting, and a method for evaluating the reliability of the material based on yield strength was proposed. The proposed methodology in this paper is of reference significance for the quantification of surface roughness and its effect on yield strength of other additive manufacturing materials and specimens.

Microscale contact and friction behavior are widely present in various important industrial devices and systems. As electromechanical systems become more integrated and miniaturized, the impact of friction on devices becomes increasingly important. At the microscale, friction behavior exhibits a strong dependence on interfacial viscosity and contact size. By developing a series of modifiable potential functions to quantitatively regulate interfacial properties, friction on atomically smooth interfaces with different properties is fully simulated using molecular dynamics methods. The study first examined the influence of various interfacial potential energies on the static friction coefficient, revealing a nonlinear relationship between the static friction coefficient and interfacial potential energy intensity. Furthermore, it was found that this nonlinearity is attributed to the competition between interfacial viscosity and contact stiffness. Additionally, the study investigated the influence of contact size on static friction coefficient. The simulation results showed that as the tangential contact length of the interface increases, the peak static friction force first increases and then stabilizes. By analyzing the contact layer cloud maps obtained through post-processing, interfacial friction is observed as a “nucleation-propagation” process, influenced by different contact sizes which affect the dynamic process and lead to changes in the peak static friction force. This study provides new insights into the effects of interfacial potential energy and contact size on microscale friction through molecular dynamics simulations, it is feasible to regulate friction by changing interfacial potential energy, but attention should be paid to the nonlinear changes in the friction coefficient. Besides, solely increasing the contact size cannot infinitely increase the peak static friction force.

The study examined the two-anchor system of Extension-Type Bamboo/Rebar Tension-Pressure (EBTP) anchor rods in earthen sites. Indoor two-anchor digital image correlation (DIC) pullout tests with anchor spacing of 0.3 m and 0.6 m were conducted to clarify the load-displacement relationship and typical failure modes. Based on the characteristics of anchor slip failure modes, a 2D finite element method (FEM) was proposed for the two-anchor system. The slurry/soil interface under compression and rod/pulp interface in tension were simulated using the contact pairs and nonlinear springs, respectively. Experimental results indicated that, at 0.3 m spacing, horizontal cracking along the rammed earth layer was the primary failure mode, while at 0.6 m spacing, a conical cracking pattern emerged with a transition between tension and compression at an angle of 30°～45°, yielding a maximum crack radius of approximately 24 cm at the soil top surface. The bearing capacity decreased by approximately 7% at 0.3 m spacing compared to 0.6 m spacing. The simulation analysis illustrates that anchor spacing has a significant influence on the group anchor effect. For one thing, when the spacing exceeds 0.6 m, the group anchor effect is more limited, which is consistent with experimental results. For another, the depth of the expansion body demonstrates an approximately linear correlation with the ultimate bearing capacity of the anchor. Therefore, as anchor length increases, the bearing capacity initially increases sharply, followed by a more moderate increase. Although the group anchor effect gradually strengthens, the increment in bearing capacity due to increased anchor length outweighs the loss caused by the group anchor effect. These findings provide valuable insights for the design of EBTP anchor groups in earthen sites. The simulation methodology in this study can be used to predict and optimize anchorage design parameters for anchoring works at earthen sites.

The mechanical properties of materials are affected by inevitable defects such as inclusions and cracks. Accurate knowledge of their elastic fields is required to prevent stress concentration, which can lead to fracture and plastic damage. To study mutual interactions in an isotropic plane with cracks and inclusions, heterogeneous inclusions are approximated as homogeneous inclusions with the same elastic modulus as the matrix plus unknown eigenstrain based on the equivalent inclusion method, while mixed-mode Ⅰ/Ⅱ cracks are approximated as climb/glide dislocations with unknown densities according to the distributed dislocation technology. Interactions in the plane are fully considered in the governing equation system, and a solvable matrix is established with all unknowns in a unified framework. The conjugate gradient method is used to iteratively solve the unknowns, and the fast Fourier transform is introduced to improve computational efficiency. The stress field of cracks in any direction is settled by the stress transformation law, and the stress intensity factors at crack tips are determined by the converged dislocation densities with the assumption of crack-induced displacements in parabolic shapes. The influence of the heterogeneous properties of inclusions on stress intensity factors at crack tips is then properly captured. The situations of cracks/inclusions are discussed in detail, providing a description of the elastic fields and stress intensity factors. The complexity does not necessarily increase with the number of inclusions and cracks, and the calculation cost depends only on the mesh density. The effectiveness of the model developed in this study is verified using the finite element method. This model has potential application prospects in the fracture failure of heterogeneous materials and the plastic zone problems near crack tips. The conclusions may offer insight into the modeling scheme of various defective structures and the fracture behavior of materials.

Using fused deposition modeling (FDM) 3D printing technology, a lattice structure was created. After adhering composite conductive materials to the surface of its structural elements, the 3D lattice structure with sensing capability (LSS) was fabricated. Based on three-unit configurations, a study was conducted to investigate the mechanical properties and piezoresistive characteristics of different lattice structures in LSS. Utilizing the conductive percolation phenomenon in conductive composites, this study explored the patterns of piezoresistive behavior in LSS with varying structures and composites under both small and large strain conditions. Key factors such as stress caused by structural deformation and self-contact between lattice surfaces were identified, leading to the observed three-stage trend in the change of electrical resistance response. By analyzing the experimental data from compression tests, the optimal lattice structure and composite mass fraction for LSS were determined, providing a reliable basis for deformation monitoring in perceptual structures. The approach of creating a 3D structure and then incorporating conductive composites offers benefits such as structural controllability and good mechanical performance. The sensing structure can detect compressive stress in objects and serve as a high-quality buffering or damping material that effectively absorbs vibration and energy. This research demonstrates promising applications in various fields.

Additive manufacturing (AM) techniques have attracted widespread attention in aerospace and biomedical fields due to advantages like high material utilization and extensive design flexibility. However, process-induced defects in AM-built components pose significant challenges for evaluating fatigue performance. The AM-built components are subjected to complex alternating loads in service, making it imperative to develop accurate fatigue life prediction models. Currently, two main approaches are widely employed: theoretical analysis and data-driven methods. Traditional life prediction models like continuum damage mechanics (CDM) suffer from limitations such as low accuracy and restricted applicability. Conversely, data-driven models, such as artificial neural networks (ANN), encounter constraints when dealing with limited sample sizes. To address these issues, knowledge-data hybrid models have emerged as a promising approach that combines physical principles with data insights. In view of this, this study has developed a calibrated CDM model and seamlessly integrated it with an ANN-based data-driven model. Employing methods of feature, parameter, and output fusion, three types of hybrid models based on CDM and ANN have been developed. To quantitatively analyze the prediction accuracy and data requirements of these models, calculations using fatigue data obtained from laser powder bed fusion (LPBF)-processed AlSi10Mg alloy have been performed. The results highlight the crucial role played by the corrective function of training data in the parameter fusion-based model, while indicating a relatively minor influence from the CDM model in terms of prediction accuracy. Moreover, this model retains a commendable level of accuracy even with suboptimal fitting outcomes from the CDM model. The hybrid model, which leverages feature fusion, maximizes the utilization of physical information from the CDM model, thus achieving the highest prediction accuracy and stability when ample data are available. The model based on output fusion, primarily guided by results of the CDM model and enhanced by ANN adjustments, demonstrates relatively superior predictive capabilities in domains outside of the training set compared to other models. These findings provide significant reference value for the further development of high-accuracy, knowledge-data hybrid fatigue life prediction models in AM.

Stress intensity factor is a crucial parameter for modeling and predicting structural fracture failure. This study evaluates the dynamic stress intensity factor for solving three-dimensional dynamic fracture problems using the adaptive phantom node method. This technique combines the phantom node method with adaptive mesh refinement, automating the generation of a dense mesh around the crack. In this approach, strong discontinuities at cracks are modeled using phantom nodes without crack tip enrichment functions or extra degrees of freedom. The theoretical framework of this technique is straightforward and easy to implement based on the finite element method, but it requires a relatively dense mesh to ensure computational accuracy. Adaptive mesh refinement technology and criteria suitable for crack problems are introduced into the phantom node method, thus obviating the need for a globally dense mesh with high computational consumption while improving computational accuracy and efficiency. A concise approach, known as constrained approximation, is adopted to deal with hanging nodes presented in the locally refined mesh. It is convenient to implement numerically, does not involve special elements or complex shape functions, and retains the interpolation and numerical integration of the standard finite element method. The stress intensity factors for several three-dimensional crack problems are evaluated using the adaptive phantom node method and compared with the theoretical solutions and numerical results obtained by the standard phantom node method. It is found that the numerical results of this method are in good agreement with the theoretical solutions, and the computational accuracy is effectively improved compared to the standard phantom node method. Additionally, compared to the locally pre-refined mesh with equivalent accuracy, the adaptive refined mesh exhibits higher computational efficiency and reduced computational consumption. This holds considerable potential value for the efficient simulation and prediction of dynamic fracture failure in large-scale complex engineering structures.