Acta Mechanica Solida Sinica最新文献

This study focused on investigating the effects of various factors on the mechanical properties of superconducting matrix composites reinforced with ferromagnetic particles and interface phases when exposed to external magnetic fields. A micromechanical model was created by simplifying the basic properties and composition of the interface, utilizing principles such as Eshelby’s equivalent inclusion theory and Hooke’s law, as well as applying uniform stress boundary conditions. Through the development of equations, the study predicted changes in effective mechanical properties, highlighting the significant influence of parameters like the interface phase, inclusions, and magnetic field on the effective elastic modulus and magnetostriction of the composite material. By shedding light on these relationships, the research offers valuable insights for the manufacture and application of ferromagnetic particle-reinforced superconducting matrix composites with interface phases, providing a foundation for future research in this area.

Graphene, a two-dimensional material with atomic thickness, holds significant importance in advancing the existing theories of solid mechanics. However, as an intersection of multiple scales, it poses challenges to experimental measurements of its mechanical behaviors. This review comprehensively discusses the recent achievements in experimental studies on the mechanics of graphene, focusing on sample preparation, loading design, and measurement techniques. Moreover, personal perspectives on the future development in this field are presented, aiming to provide insights and inspiration for researchers engaged in related studies.

Lithium metal batteries have been deemed one of the most promising candidates for new-generation batteries, used in mobile devices, electric vehicles, energy storage, etc. However, due to the volume change of active materials and external pressure, the electrode materials and interfaces between battery components have high stresses during the cycling process, resulting in large deformation of the lithium metal anode. Herein, we derive insights into the mechanical behaviors of polycrystalline lithium metal. Specifically, the mechanical properties of lithium metal containing Li_7-xLa₃Zr_2-xTa_xO₁₂ (x = 0.2–0.7) (LLZTO) solid-state electrolyte impurities are experimentally investigated. It is found that its strength is governed by impurity content and impurity particle size. In addition, we explore the Hall–Petch and inverse Hall–Petch effects of nanocrystalline lithium through atomic-scale simulations, revealing the plastic deformation mechanism in polycrystalline lithium metal. This fundamental study sheds light on the impurity-modulated mechanical properties and plastic deformation mechanism of polycrystalline lithium metal.

Nickel-based alloys are the primary structural materials in steam generators of high-temperature gas reactors. To understand the irradiation effect of nickel-based alloys, it is necessary to examine dislocation movement and its interaction with irradiation defects at the microscale. Hardening due to voids and Ni₃Al precipitates may significantly impact irradiation damage in nickel-based alloys. This paper employs the molecular dynamics method to analyze the interaction between edge dislocations and irradiation defects (void and Ni₃Al precipitates) in face-centered cubic nickel. The effects of temperature and defect size on the interaction are also explored. The results show that the interaction process of the edge dislocation and irradiation defects can be divided into four stages: dislocation free slip, dislocation attracted, dislocation pinned, and dislocation unpinned. Interaction modes include the formation of stair-rod dislocations and the climbing of extended dislocation bundles for voids, as well as the generation of stair-rod dislocation and dislocation shear for precipitates. Besides, the interactions of edge dislocations with voids and Ni₃Al precipitates are strongly influenced by temperature and defect size.

Two-dimensional (2D) materials are promising for next-generation electronic devices and systems due to their unique physical properties. The interfacial adhesion plays a vital role not only in the synthesis, transfer and manipulation of 2D materials but also in the manufacture, integration and performance of the functional devices. However, the atomic thickness and limited lateral dimensions of 2D materials make the accurate measurement and modulation of their interfacial adhesion energy challenging. In this review, the recent advances in the measurement and modulation of the interfacial adhesion properties of 2D materials are systematically combed. Experimental methods and relative theoretical models for the adhesion measurement of 2D materials are summarized, with their scope of application and limitations discussed. The measured adhesion energies between 2D materials and various substrates are described in categories, where the typical adhesion modulation strategies of 2D materials are also introduced. Finally, the remaining challenges and opportunities for the interfacial adhesion measurement and modulation of 2D materials are presented. This paper provides guidance for addressing the adhesion issues in devices and systems involving 2D materials.

Silicon, a leading candidate for electrode material for lithium-ion batteries, has garnered significant attention. During the initial lithiation process, the alloying reaction between silicon and lithium transforms the pristine silicon microstructure from crystalline to amorphous, resulting in plastic deformation of the amorphous phase. This study proposes the free volume theory to develop a fully coupled Cahn–Hilliard phase-field model that integrates viscoplastic deformation, free volume evolution, and diffusion. This model investigates the chemophysical phenomenon of self-limiting behavior occurring during the initial lithiation of silicon anodes. Unlike most existing models, the proposed model considers free volume-dependent diffusion using a physically-based approach. The model’s temporal variation in the lithiated phase thickness aligns well with experimental results, confirming the model’s accuracy. Stress field calculations reveal the coexistence of compressive and tensile stresses within the lithiated phase, which may not cause the limiting effect under the frame of the stress-induced diffusion. Analyses indicate that high effective stress increases free volume, enhancing lithium diffusion and augmenting the diffusion coefficient. Reducing the diffusion coefficient in the lithiated phase due to free volume evolution is the primary cause of self-limiting lithiation.

Twisted polymer artificial muscles activated by thermal heating represent a new class of soft actuators capable of generating torsional actuation. The thermal torsion effect, characterized by the reversible untwisting of twisted fibers as temperature increases due to greater radial than axial thermal expansion, is crucial to the actuation performance of these artificial muscles. This study explores the thermal torsion effect of polymer muscles made of twisted Nylon 6 fibers in experimental and theoretical aspects, focusing on the interplay between material properties and temperature. It is revealed that the thermal torsion effect enhances the actuation performance of the twisted polymer actuator while the thermal softening effect diminishes it. A thermal–mechanical model incorporating both the thermal torsion effect and thermal softening effect is used to predict the recovered torque of the twisted polymer actuators. An optimal bias angle and operating temperature are identified to maximize the recovered torque. Analysis of strain and stress distributions in the cross-section of the twisted polymer fiber shows that the outer layers of the fiber predominantly contribute to the torsional actuation. This work aids in the precise control and structural optimization of the thermally-activated twisted polymer actuators.

To overcome the challenges of limited experimental data and improve the accuracy of empirical formulas, we propose a low-cycle fatigue (LCF) life prediction model for nickel-based superalloys using a data augmentation method. This method utilizes a variational autoencoder (VAE) to generate low-cycle fatigue data and form an augmented dataset. The Pearson correlation coefficient (PCC) is employed to verify the similarity of feature distributions between the original and augmented datasets. Six machine learning models, namely random forest (RF), artificial neural network (ANN), support vector machine (SVM), gradient-boosted decision tree (GBDT), eXtreme Gradient Boosting (XGBoost), and Categorical Boosting (CatBoost), are utilized to predict the LCF life of nickel-based superalloys. Results indicate that the proposed data augmentation method based on VAE can effectively expand the dataset, and the mean absolute error (MAE), root mean square error (RMSE), and R-squared (R²) values achieved using the CatBoost model, with respective values of 0.0242, 0.0391, and 0.9538, are superior to those of the other models. The proposed method reduces the cost and time associated with LCF experiments and accurately establishes the relationship between fatigue characteristics and LCF life of nickel-based superalloys.

The stress wave profile at the frictional interface is crucial for investigating the frictional process. This study modeled a brittle material interface with a micro- contact to analyze the fine stress wave structure associated with frictional slip. Employing the finite element simulation alongside the related wave theory and experiments, two new wave structures were indentified: A Mach cone symmetric to the frictional interface associated with incident plane wave propagation, and a new plane longitudinal wave generated across the entire frictional interface at the moment when the incident wave began to propagate. The time and space of its appearance implies that the overall response of the frictional interface precedes the local wave response of the medium. Consequently, a model involving characteristic line theory and the idea of Green’s function has been proposed for its occurrence. The analysis results show that these two new wave phenomena are independent of the fracture of micro-contacts at the interface; instead, the frictional interface effect may be responsible for the generation of such new wave structures. The measured wave profiles provide a proof for the existence of the new wave structures. These results display new wave phenomena, and suggest a wave profile for investigating the dynamic mechanical properties of the frictional interface.

The largely bending bilayer electrode model battery has been widely used to measure the mechanical properties of composite electrode materials. The assumption used in the method that lithium is uniformly distributed in the active layer lacks quantitative evaluation, and the uniformity of concentration distribution is crucial for accurate in-situ measurements of concentration-related material properties and stress in bilayer electrodes. Therefore, this paper proposes a mechanical-electrochemical coupled model to study the lithium concentration distribution in the active layer during lithiation. This model includes lithium concentration diffusion and active layer deformation. By comparing experimental and simulated curvature evolution of the active layer during lithiation and delithiation, the reliability of this simulation model is verified. We then derive the precise concentration distribution inside the active layer and suggest using relative error to quantitatively evaluate the uniformity of lithium concentration in the active layer. Results show that a low relative error in lithium concentration can be achieved in the middle region of the active layer. Additionally, the effects of different rates and geometric parameters on the lithium concentration distribution in the active layer are discussed. Results indicate that reduced rates, thinner active layers, shorter active layer lengths, and increased spacing between the working and counter electrodes can lead to a more uniform distribution of lithium concentration in the active layer. These insights help improve experimental methods and equipment, promoting uniform distribution of lithium in the active layer and enhancing measurement accuracy.