今日更新：International Journal of Solids and Structures 1 篇，Journal of the Mechanics and Physics of Solids 1 篇，Mechanics of Materials 1 篇，Thin-Walled Structures 4 篇International Journal of Solids and StructuresEffect of an edge dislocation on hydride growth in zirconium: Elastic complex potential studyC.Y. Liu, L.N. Li, C. Xiedoi:10.1016/j.ijsolstr.2024.112870边缘位错对锆中氢化物生长的影响:弹性络合电位研究The formation of hydrides can significantly decrease the mechanical reliability of Zr servicing in the nuclear reactor. This study investigates the effect of the local stress field resulting from the hydride eigenstrain and dislocations on hydrogen transport and explores the hydride growth regulation. The stress functions, which can be extended and further applied to the realistic crystal structure and servicing status, are derived using the dislocation-based strain nucleus model and elastic complex potential method. The nonhomogeneous equation of hydrogen transport governed by diffusion and hydrostatic stress gradient is analytically solved. The results show that: (1) In the absence of dislocations, the hydride grows toward 112¯0 direction under the hydrostatic stress gradient resulting from the hydride eigenstrain. (2) The lower the temperature is, the higher the hydrogen concentration gradient in the adjacent area of the hydride is. The higher hydrogen fraction can also accelerate the growth rate. (3) Dislocation defects are capable of inducing triangle-shaped and asymmetric growth tendencies and providing new nucleation loci for hydrides. Based on the significant hydrostatic stress gradient led by dislocation singularity, this study analytically explains the autocatalysis and new-nucleation-locus effects raised by the in-situ observations.氢化物的形成会大大降低核反应堆中锆材料的机械可靠性。本研究调查了氢化物特征应变和位错产生的局部应力场对氢传输的影响，并探讨了氢化物生长的调节。利用基于位错的应变核模型和弹性复势方法，推导出了应力函数，该函数可扩展并进一步应用于现实的晶体结构和维修状态。分析求解了受扩散和静水应力梯度支配的氢传输非均质方程。结果表明 (1) 在没有位错的情况下，氢化物在氢化物特征应变产生的静应力梯度作用下向 112¯0 方向生长。(2) 温度越低，氢化物邻近区域的氢浓度梯度越高。较高的氢分量也会加快生长速度。(3) 位错缺陷能够诱发三角形和不对称生长倾向，并为氢化物提供新的成核位置。本研究基于位错奇异性导致的显著静水应力梯度，分析解释了原位观测所提出的自催化和新成核点效应。Journal of the Mechanics and Physics of SolidsA micromechanical scheme with nonlinear concentration functions by physics-guided neural networkCe Chen, Liujun Wu, Jiaqi Fu, Chenyang Xin, Wenbin Liu, Huiling Duandoi:10.1016/j.jmps.2024.105681基于物理导向神经网络的非线性集中函数微力学方案The mechanical behavior of heterogeneous materials has been reported to be significantly influenced by the nonlinear properties of both the matrix and interface. However, the micromechanical homogenization methods for predicting the effective properties are challenged in nonlinear problems due to the difficulties in solving the analytical form of the concentration tensors. In this study, we develop a nonlinear micromechanical scheme for heterogeneous materials with complex interfacial behaviors, where the key component, namely nonlinear concentration functions, is determined by the devised physics-guided neural network. In particular, the nonlinear Mori–Tanaka method (NMT) implemented within this new micromechanical scheme yields accurate solutions to axisymmetric nonlinear homogenization problems considering the effects of finite deformation, loading conditions, volume fraction, etc. Furthermore, the NMT is equivalent to the linear Mori–Tanaka method in the condition of the small deformation. Notably, this neural-network-based micromechanical scheme shows good generalization for different types of nonlinear interfaces, while the corresponding approach for generating training data via the finite element method (FEM) is cost-effective. This theoretical framework introduces a novel approach to nonlinear physical modeling, namely, not by the direct regression from the dataset but by deeply embedding neural networks in physical laws.非均相材料的力学行为受到基体和界面非线性特性的显著影响。然而，由于难以求解浓度张量的解析形式，用于预测有效性质的微力学均匀化方法在非线性问题中受到挑战。在这项研究中，我们开发了具有复杂界面行为的非均质材料的非线性微力学方案，其中关键成分，即非线性浓度函数，由设计的物理引导神经网络确定。特别是，在这种新的微力学方案中实现的非线性Mori-Tanaka方法(NMT)可以精确地解决考虑有限变形，加载条件，体积分数等影响的轴对称非线性均匀化问题。此外，在小变形条件下，NMT与线性Mori-Tanaka方法等效。值得注意的是，这种基于神经网络的微力学方案对不同类型的非线性界面具有良好的泛化性，而通过有限元方法生成训练数据的相应方法具有成本效益。该理论框架引入了一种新的非线性物理建模方法，即不是通过数据集的直接回归，而是通过将神经网络深度嵌入物理定律。Mechanics of MaterialsHydrogen diffusion behavior within microstructures near crack tip: A crystal plasticity studyKaidi Li, Bin Tang, Mengqi Zhang, Jinhua Dai, Xichuan Cao, Bangqi Yin, Zhenshun Zhang, Jiangkun Fan, Jinshan Lidoi:10.1016/j.mechmat.2024.105032裂纹尖端附近微结构中氢的扩散行为:晶体塑性研究The hydrogen diffusion and damage characteristics within the microstructure at the crack tip are direct factors determining hydrogen embrittlement (HE) phenomena, yet research in this area from a mesoscale perspective is still insufficient. This study employs a non-local crystal plasticity constitutive model coupled with a hydrogen diffusion model that considers grain boundary (GB) characteristics and incorporates fracture initiation parameter accounting for the HELP+HEDE mechanisms. The research investigates hydrogen diffusion behavior at the crack tip in pure nickel and provide a detailed exploration of the mechanism underlying hydrogen-assisted crack propagation. The results indicate that the non-local model exhibits advantages in simulating the hydrogen diffusion process. Hydrogen induces intragranular cracks to propagate along slip planes with a high dislocation density. High-energy GBs and triple junctions are more susceptible to hydrogen accumulation, and under the influence of the HEDE mechanisms, they represent the primary sites for crack initiation. The entire fracture process involves the continuous coalescence of primary cracks with secondary cracks. Moreover, the HE resistance is better in equiaxed microstructures compared to rolled microstructures, particularly when the crack plane is parallel to the TD direction.裂纹尖端微观组织内氢的扩散和损伤特征是决定氢脆现象的直接因素，但从中尺度角度对氢脆现象的研究尚显不足。本研究采用非局部晶体塑性本构模型与氢扩散模型耦合，该模型考虑了晶界(GB)特征，并纳入了HELP+HEDE机制的断裂起裂参数。研究了纯镍中氢在裂纹尖端的扩散行为，并对氢辅助裂纹扩展的机制进行了详细的探索。结果表明，非局部模型在模拟氢气扩散过程中具有优势。氢诱导晶内裂纹沿滑移面扩展，位错密度高。高能GBs和三重结更容易发生氢气积聚，在HEDE机制的影响下，它们是裂纹起裂的主要部位。整个断裂过程是原生裂缝与次生裂缝的连续贯通过程。此外，等轴组织的HE抗力优于轧制组织，特别是当裂纹平面平行于TD方向时。Thin-Walled StructuresMechanical issues of lithium-ion batteries in road traffic conditions: a reviewYue Liu, Yongjun Pan, Huacui Wang, Honggang Li, Huanhuan Bao, Zhiwei Zhao, Binghe Liudoi:10.1016/j.tws.2024.111985道路交通条件下锂离子电池的力学问题综述The escalating challenges of the energy crisis and environmental pollution have propelled the development of the lithium-ion battery (LIB) industry as a response to the demand for low-carbon solutions. Known for its high energy density, extended lifespan, and robust stability, LIB has become the preferred power source for electric vehicles, with safety concerns demanding significant attention. Mechanical abuse stands out as a significant contributor to battery fire and explosion incidents, prompting the establishment of safety standards and heightened concerns in this regard. According to the road traffic conditions, mechanical abuse is categorized into three forms: vibration, mechanical shock, and crash in this review. Each is individually discussed, covering corresponding real traffic scenarios, relevant safety standards, and experimental methodologies. The review then delves into the failure behaviors including mechanical, electrochemical and thermal performance, and the associated observation methods. Finally, existing mechanical modeling methods and their applications are summarized. The paper aims to comprehensively explore the mechanical abuse behaviors and research methodologies applicable to LIBs in traffic scenarios, ultimately providing engineering guidance to enhance the safety performance of LIBs.能源危机和环境污染的挑战不断升级，推动了锂离子电池(LIB)行业的发展，以满足对低碳解决方案的需求。LIB以其高能量密度、长寿命和强大的稳定性而闻名，已成为电动汽车的首选电源，安全性问题需要引起高度重视。机械滥用是电池火灾和爆炸事件的重要原因，促使安全标准的建立，并引起人们对这方面的高度关注。根据道路交通状况，本文将机械滥用分为振动、机械冲击和碰撞三种形式。每个单独讨论，涵盖相应的真实交通场景，相关的安全标准和实验方法。然后，综述深入研究了失效行为，包括力学，电化学和热性能，以及相关的观察方法。最后，总结了现有的力学建模方法及其应用。本文旨在全面探索交通场景下桥架的力学滥用行为和研究方法，最终为桥架的安全性能提升提供工程指导。A deviatoric couple stress Mindlin plate model and its degenerationYa-Wei Wang, Jian Chen, Xian-Fang Lidoi:10.1016/j.tws.2024.111978偏偶应力Mindlin板模型及其退化Based on the classical couple stress theory, the deviatoric couple stress theory (DCST), where both couple stress and curvature tensors are traceless, is developed. The deviatoric couple stress Mindlin plate is established based on a new hypothesis of the vanishing curvature of the transverse normal, and the governing equations and associated boundary conditions of the simplified size-dependent Mindlin plate are respectively derived by the principle of virtual work. In the absence of couple stresses, a simplified Mindlin plate model between the classical Kirchhoff plate model and classical Mindlin plate model is derived. To illustrate the simplified DCST-based Mindlin plate model, the static bending and free vibration of rectangular plates are studied. The dependence of the length scale parameter and curvature ratio on the deflection, rotations and natural frequency is analyzed. The numerical results show that the consideration of couple stresses and curvatures hardens the stiffness of the microstructure, resulting in a decrease in its deflection and rotation compared with that of the macroscopic structure under the same conditions, while the natural frequency increases, which is consistent with the size effect observed in experiments.在经典耦合应力理论的基础上，提出了耦合应力和曲率张量均无迹的偏耦应力理论(DCST)。基于横法线曲率消失的新假设，建立了偏偶应力明林板，并利用虚功原理推导了简化尺寸相关明林板的控制方程和边界条件。在没有耦合应力的情况下，推导了经典Kirchhoff板模型和经典Mindlin板模型之间的简化Mindlin板模型。为了说明基于dst的简化Mindlin板模型，对矩形板的静弯曲和自由振动进行了研究。分析了长度尺度参数和曲率比对挠度、旋转和固有频率的依赖关系。数值结果表明，考虑应力和曲率的耦合作用使微结构刚度变硬，与宏观结构相比，在相同条件下微结构的挠度和旋转减小，而固有频率增加，这与实验观察到的尺寸效应一致。Achieving excellent strength-ductility combination of Al-aided Mg-Gd-Al-Zr-Zn alloys fabricated by cold metal transfer-based wire-arc directed energy deposition via uniform equiaxed grains and multiple precipitatesChen Ji, Kun Li, Tianbao Yang, Shengwen Bai, David Z. Zhang, Lawrence E. Murr, Bin Jiang, Fusheng Pandoi:10.1016/j.tws.2024.111980 通过均匀的等轴晶和多析出相，采用冷金属转移为基础的线弧定向能沉积制备了al辅助Mg-Gd-Al-Zr-Zn合金，实现了优异的强度-塑性组合Limited ductility consistently poses a challenge for high-strength Mg-RE (rare earth) structures prepared by additive manufacturing. Particularly following heat treatment, while the strength of the Mg-RE alloy experiences a substantial increase, there is a noteworthy decrease in its ductility. Herein, a novel Mg-Gd-Al-Zr-Zn thin wall was successfully fabricated by cold metal transfer-based wire-arc directed energy deposition (CMT-WA-DED) and Al alloying. The microstructural evolution and mechanical properties of deposited and heat-treatment alloys were elucidated systematically. By adding Al element, Al2Gd and Al-Zr phases with thermal stability were precipitated in the deposited alloy. During the solidification or heat treatment stage, Al2Gd and Al-Zr phases could pin grain boundaries to restrict grain growth. The as-deposited alloys exhibited fully equiaxed grains at different heights and orientations. Thus, the thin wall exhibited good isotropic performance. After the heat treatment, the grain size only slightly grew and no abnormal grain growth was observed. Various morphologies of β precipitation phases were discovered along grain boundaries and within the grains. Additionally, a high density of β' and β1 phases within the grains and β phases along the grain boundary played pivotal roles in enhancing the mechanical strength of the Mg-Gd-Al-Zr-Zn alloy. The alloys exhibited an excellent combination of strength and ductility with ultimate tensile strength of 340 ± 7 MPa, yield strength of 212 ± 5 MPa, and elongation of 12.7 ± 0.9%. This work provides theoretical and practical reference value for the Mg-RE structures obtaining an excellent combination of strength and ductility prepared by additive manufacturing.有限的延展性一直是增材制造制备高强度Mg-RE(稀土)结构的挑战。特别是热处理后，Mg-RE合金的强度大大提高，但其延展性明显下降。在此基础上，采用冷金属转移基线弧定向能沉积(CMT-WA-DED)和铝合金化技术成功制备了新型Mg-Gd-Al-Zr-Zn薄壁材料。系统地阐述了沉积合金和热处理合金的组织演变和力学性能。通过添加Al元素，沉积合金中析出具有热稳定性的Al2Gd和Al- zr相。在凝固或热处理阶段，Al2Gd和Al-Zr相可以固定晶界，限制晶粒长大。沉积合金在不同高度和取向上均表现出完全等轴晶粒。因此，薄壁具有良好的各向同性性能。热处理后晶粒尺寸略有增大，未见异常晶粒长大。沿晶界和晶粒内部发现了不同形态的β析出相。晶粒内高密度的β′和β1相以及沿晶界的β相对Mg-Gd-Al-Zr-Zn合金机械强度的提高起着关键作用。合金的抗拉强度为340±7 MPa，屈服强度为212±5 MPa，延伸率为12.7±0.9%，具有良好的强度和延展性。该工作为增材制造制备的镁稀土合金结构获得良好的强度和延展性提供了理论和实践参考价值。A new buckling model for thin-walled micro-beams based on modified gradient elasticity: coupling effect and size effectBing Zhao, Huanxin Yi, Shiren Lin, Andi Lai, Chengyun Long, Jian Chendoi:10.1016/j.tws.2024.111983 基于修正梯度弹性的薄壁微梁屈曲新模型:耦合效应和尺寸效应More and more thin-walled micro-beams, including the I-section thin-walled micro-beams, are applied in MEMS. The buckling of a thin-walled micro-beam exhibits some different phenomena from that of a large scale thin-walled beam, such as the size effect, and the coupling effects caused by strain gradient. To investigate the influence of the coupling effects and size effect on the buckling of thin-walled micro-beams, a new buckling model is proposed. Based on modified gradient elasticity (MGE), the governing equations and boundary conditions of the new model are derived from the variational principle. The governing equations and boundary conditions can be simplified to the classical Vlasov's theory, the MGE Bernoulli-Euler beam model, MGE Bernoulli-Euler beam model considering bi-directional flexure respectively. Solved by the feature expansion method, the size effects of the thin-walled micro-beam can be captured by the new model, that is the buckling load increases with internal length scales. Besides the classical flexural-torsional coupling effect, two new coupling effects, such as the higher-order flexure-flexure coupling and the higher-order flexural-torsional coupling, are also captured by the new model. These two new high-order coupling effects of the new model reduce the critical buckling load of thin-walled micro-beams. The higher-order flexural-flexural coupling effect is far greater than the other two coupling effects, and the higher-order flexural-flexural coupling effect is on the same order of magnitude as the effect of MGE (size effect), with the former being negative and the latter positive. The size effect and higher-order coupling effect cannot be ignored and need to be considered carefully for the buckling of thin-walled micro-beams.越来越多的薄壁微梁，包括工字截面薄壁微梁在微机电系统中的应用。薄壁微梁的屈曲表现出与大尺度薄壁梁不同的现象，如尺寸效应、应变梯度引起的耦合效应等。为了研究耦合效应和尺寸效应对薄壁微梁屈曲的影响，提出了一种新的屈曲模型。基于修正梯度弹性理论，利用变分原理推导了新模型的控制方程和边界条件。控制方程和边界条件可分别简化为经典Vlasov理论、MGE伯努利-欧拉梁模型和考虑双向挠曲的MGE伯努利-欧拉梁模型。通过特征展开法求解，新模型可以捕捉到薄壁微梁的尺寸效应，即屈曲载荷随内长度尺度的增大而增大。除了经典的弯扭耦合效应外，该模型还捕获了两种新的耦合效应，即高阶弯扭耦合和高阶弯扭耦合。新模型的这两个新的高阶耦合效应降低了薄壁微梁的临界屈曲载荷。高阶弯弯耦合效应远大于其他两种耦合效应，且高阶弯弯耦合效应与MGE效应(尺寸效应)在同一个数量级上，前者为负，后者为正。对于薄壁微梁的屈曲，尺寸效应和高阶耦合效应是不可忽视的，需要认真考虑。来源：复合材料力学仿真Composites FEM
