今日更新：Journal of the Mechanics and Physics of Solids 1 篇，Mechanics of Materials 1 篇，International Journal of Plasticity 1 篇，Thin-Walled Structures 5 篇Journal of the Mechanics and Physics of SolidsQuantized plastic deformationN. Perchikov, L. Truskinovskydoi:10.1016/j.jmps.2024.105704量子化塑性变形In engineering crystal plasticity inelastic mechanisms correspond to tensorial zero-energy valleys in the space of macroscopic strains. The flat nature of such valleys is in contradiction with the fact that plastic slips, mimicking lattice-invariant shears, are inherently discrete. A reconciliation has recently been achieved in the mesoscopic tensorial model (MTM) of crystal plasticity, which introduces periodically modulated energy valleys while also capturing in a geometrically exact way the crystallographically-specific aspects of plastic slips. In this paper, we extend the MTM framework, which in its original form had the appearance of a discretized nonlinear elasticity theory, by explicitly introducing the concept of plastic deformation. The ensuing model contains a novel matrix-valued spin variable, representing the quantized plastic distortion, whose rate-independent evolution can be described by a discrete (quasi-)automaton. The proposed reformulation of the MTM leads to a considerable computational speedup associated with the use of a robust and efficient hybrid Gauss–Newton–Cauchy energy minimization algorithm. To illustrate the effectiveness of the new approach, we present a detailed case-study focusing on the aspects of crystal plasticity that are beyond reach for the classical continuum theory. Thus, we provide compelling evidence that the re-formulated MTM is fully adequate to deal with the intermittency of plastic response under quasi-static loading. In particular, our numerical experiments show that the statistics of dislocational avalanches, associated with plastic yield in 2D square crystals, exhibits a power-law tail with a critical exponent matching the value predicted by general theoretical considerations and also independently observed in discrete-dislocation-dynamics (DDD) simulations.在工程晶体塑性中，非弹性机制对应于宏观应变空间中的张量零能谷。这种谷的平坦性质与塑性滑移(模仿晶格不变剪切)本质上是离散的这一事实相矛盾。最近在晶体塑性的介观张量模型(MTM)中实现了调和，该模型引入了周期性调制的能量谷，同时也以几何精确的方式捕获了塑性滑移的晶体学特定方面。本文通过明确地引入塑性变形的概念，对MTM框架进行了扩展，MTM框架在其原始形式中具有离散非线性弹性理论的外观。随后的模型包含一个新的矩阵值自旋变量，表示量子化的塑性变形，其速率无关的演化可以用离散(准)自动机来描述。提出的MTM的重新表述导致了与使用鲁棒和高效的混合高斯-牛顿-柯西能量最小化算法相关的相当大的计算速度。为了说明新方法的有效性，我们提出了一个详细的案例研究，重点关注经典连续介质理论无法达到的晶体塑性方面。因此，我们提供了令人信服的证据，证明重新制定的MTM完全足以处理准静态载荷下塑性响应的间歇性。特别是，我们的数值实验表明，与二维方形晶体的塑性屈服相关的位错雪崩统计数据显示出幂律尾巴，其临界指数与一般理论考虑预测的值相匹配，并且在离散位错动力学(DDD)模拟中也独立观察到。Mechanics of MaterialsCreep Behavior and Fracture Mechanism of an Additively Manufactured 316L Stainless Steel with Extraordinary Creep ResistanceYujie Pan, Huayan Hu, Kangkang Wang, Naijian Dong, Rui Qiu, Jian-Feng Wen, Miao Song, Shan-Tung Tudoi:10.1016/j.mechmat.2024.105053增材制造316L不锈钢的蠕变行为及断裂机理The creep behaviors of laser powder bed fusion (LPBF) additively manufactured (AM) 316L stainless steel (SS) and its recrystallized (Re) counterpart were investigated via uniaxial constant-load creep tests at 600 °C with nominal stress levels ranging from 235 to 360 MPa. Anisotropic creep behavior was observed in AM 316L SS, with superior creep resistance but inferior creep ductility in the horizontal sample (loaded perpendicular to the build direction (BD)) compared to the vertical sample (loaded parallel to the BD). This superior creep resistance was likely resulted from shorter dislocation slip distance and the inferior creep ductility was due to faster propagation of cracks along the columnar grain boundaries. Compared with both the Re counterpart and conventional 316L SS, AM 316L SS in this study exhibited an extraordinary creep resistance at various stress levels, with the minimum creep rate being two to three orders of magnitude lower and much longer creep life. This exceptional creep resistance of AM 316L SS was attributed to the presence of dislocation cells that impeded the deformation-induced dislocations. This led to a remarkably low rate of creep deformation and delayed the creep crack initiation, ultimately resulting in a long creep life. The gradual development of the precipitate films enriched with Mo, Si and Cr along high-angle grain boundaries, following prolonged exposure to high temperatures, was found to restrict the creep ductility in AM 316L under low stress conditions. Nevertheless, the study demonstrates that the stable dislocation cells are beneficial in enhancing the high-temperature creep resistance of AM 316L SS.在600℃、235 ~ 360 MPa的单轴恒载蠕变条件下，研究了激光粉末床熔融(LPBF)增材制造(AM) 316L不锈钢(SS)及其再结晶(Re)不锈钢的蠕变行为。在AM 316L SS中观察到各向异性蠕变行为，水平加载(垂直于施工方向)的蠕变抗力优于垂直加载(平行于施工方向)的蠕变延性。这种优异的抗蠕变性能可能是由于较短的位错滑移距离，而较差的蠕变延展性是由于裂纹沿柱状晶界扩展较快。与Re材料和常规316L SS相比，AM 316L SS在各种应力水平下都表现出非凡的抗蠕变性能，最小蠕变速率降低了2到3个数量级，蠕变寿命更长。AM 316L SS的这种优异的抗蠕变性能是由于位错细胞的存在阻碍了变形引起的位错。这使得蠕变变形速率非常低，延迟了蠕变裂纹的发生，最终获得了较长的蠕变寿命。在低应力条件下，AM 316L在高角度晶界上逐渐形成富含Mo、Si和Cr的析出膜，限制了AM 316L的蠕变延展性。然而，研究表明，稳定的位错细胞有利于提高AM 316L SS的高温蠕变抗力。International Journal of PlasticityStructural characteristics of irrational Type-II Twin interfacesAhmed Sameer Khan Mohammed, Huseyin Sehitogludoi:10.1016/j.ijplas.2024.104016 不合理ii型孪晶界面的结构特征The Type-II Twin Boundary (TB) is a critical interface in functional materials whose irrational Miller-index identity has recently drawn significant research interest. This study establishes general structural characteristics of the Type-II twin interface, utilizing TBs in Shape Memory Alloys (SMAs) - TiPd, TiPt, and AuCd - as study targets. It is shown how the irrational identity of each TB is explained by the Terrace-Disconnection (T-D) structural topology. It is proposed that the terrace is the rational-plane nearest to the irrational TB in the reciprocal space, having integral Miller-indices of least magnitude. Crystallographic-registry on this terrace requires non-trivial coherence-strains. A novel kinematic-origin of the coherence-strain is proposed, coming directly from a transformation of the classical twinning deformation-gradient. This transformation revealed that the classical twinning-shear partitions into the coherence-strain and a new metric termed the “terrace-shear”. It is shown that the magnitude of shear relating the twin-structure to the matrix is the terrace-shear and not the twinning-shear, contrary to classical understanding. Furthermore, the Burgers vector of the twinning disconnection is shown to be related directly to the terrace-shear. The energy of each Type-II interface is determined from ab initio Density Functional Theory (DFT) calculations. It is shown that the energy-minimal atomic-structure on the terrace requires determination of a “lattice-offset” that is non-trivial and unknown apriori. In summary, this study expounds on T-D topological structure of Type-II twin interfaces, establishing methods to identify rational terraces, coherence strains, ab initio planar TB energies and revealing a unique partitioning of the twinning-shear exhibited by this class of interfaces.ii型孪晶界(TB)是功能材料中的一个重要界面，其非理性的米勒指数同一性近年来引起了人们的极大兴趣。本研究利用形状记忆合金(sma)中的TBs - TiPd、TiPt和AuCd -作为研究对象，建立了ii型孪晶界面的一般结构特征。它显示了每个TB的不合理身份是如何通过梯田-断开(T-D)结构拓扑来解释的。提出阶地是在倒易空间中最接近无理数TB的有理数平面，它的积分米勒指数最小。在这个平台上的晶体学注册需要非平凡的相干应变。提出了一种新的相干应变的运动学原点，直接来自经典孪晶变形梯度的变换。这一转变揭示了经典的孪生剪切分裂为相干应变和一种新的称为“梯田剪切”的度量。结果表明，与传统的认识相反，双结构对基体的剪切强度是阶地剪切而不是孪生剪切。此外，孪生断裂的Burgers矢量与梯田剪切直接相关。每个ii型界面的能量由从头算密度泛函理论(DFT)计算确定。证明了平台上的能量最小原子结构需要确定一个非平凡且先验未知的“晶格偏移”。综上所述，本研究阐述了ii型孪晶界面的T-D拓扑结构，建立了识别合理阶地、相干应变、从头算平面TB能量的方法，揭示了这类界面所表现出的独特的孪晶剪切分配。Thin-Walled StructuresCritical Size and Internal Force Analysis of Tendril-inspired Spontaneous Helicalization MechanismZeyi Zhang, Changguo Wangdoi:10.1016/j.tws.2024.112036卷须自发螺旋化机构的临界尺寸及内力分析Tendrils initially exhibit straight morphologies before gradually transforming into helical conformations during longitudinal growth. Tendril-inspired helical structures possess advantageous physical properties and functions including versatile morphologies, adaptability, enhanced strength, and scalability. With advancements in nanoscience and nanotechnology, helical architectures across various length scales have been discovered or artificially synthesized. However, the fundamental mechanisms underlying the formation and evolution of helical structures remain elusive. This lack of mechanistic insight has impeded the controlled design and fabrication of helical structures, especially three-dimensional functional devices with integrated helical motifs. Here a mechanical model is systematically proposed for the spontaneous formation of the helical structures, based on the hypothesis of decoupled curling and warping phases. Applying nonlinear elasticity theory, a detailed analysis of the energetics and thermodynamics is presented, accounting for the large deformation that may emerge during planar curling. Additionally, differential relations between internal forces and associated displacements induced by bending and twisting of a slender curved beam under out-of-plane loading are derived, obtaining solutions via Laplace and inverse transforms. The theoretical solutions closely match ex- perimental evidence from shape memory polymers. Furthermore, the theoretical model is utilized to guide the fabrication of the smart helical antenna proposed in our previous work, and discuss the influence of configuration changes on the electromagnetic properties. Elucidating these fundamental mechanisms will facilitate the development of next-generation technologies exploiting helical architectures for diverse applications including flexible electronics, optics, and soft robotics.卷须最初呈直状，在纵向生长过程中逐渐转变为螺旋状。卷须启发的螺旋结构具有优越的物理特性和功能，包括多种形态、适应性、增强的强度和可扩展性。随着纳米科学和纳米技术的进步，各种长度尺度的螺旋结构已经被发现或人工合成。然而，螺旋结构形成和演化的基本机制仍然是难以捉摸的。由于缺乏对机械结构的了解，螺旋结构的控制设计和制造受到了阻碍，特别是具有集成螺旋图案的三维功能器件。本文基于解耦的卷曲和翘曲阶段假设，系统地提出了螺旋结构自发形成的力学模型。应用非线性弹性理论，对平面卷曲过程中可能产生的大变形进行了详细的热力学和热力学分析。此外，推导了细长弯曲梁在面外荷载作用下的内力与弯曲和扭转引起的相关位移之间的微分关系，并通过拉普拉斯变换和逆变换得到了解。理论解与形状记忆聚合物的实验证据非常吻合。利用该理论模型指导了本文提出的智能螺旋天线的制作，并讨论了结构变化对其电磁特性的影响。阐明这些基本机制将促进下一代技术的发展，将螺旋结构用于各种应用，包括柔性电子、光学和软机器人。Effects of differential hardening on energy absorption prediction of AA6061-T6 thin-walled rectangular tubeSongchen Wang, Hongchun Shang, Can Zhou, Miao Han, Yanshan Loudoi:10.1016/j.tws.2024.112050 差异硬化对AA6061-T6薄壁矩形管能量吸收预测的影响In this study, the energy absorption characteristics and deformation modes of AA6061-T6 thin-walled rectangular tube are investigated experimentally and numerically under different crushing conditions, including axial crushing, three-point bending and oblique crushing. Mechanical tests are carried out on four specimens of uniaxial tension, uniaxial compression, shear and plane strain tension along different loading directions for AA6061-T6. Besides, the effect of differential hardening behavior on the energy absorption prediction of AA6061-T6 rectangular tubes is illustrated by comparing Lou2022, von Mises and SY2009 functions. The mechanical experiment results indicate that AA6061-T6 shows obvious anisotropy, differential hardening behavior and tension-compression asymmetry, and its plastic evolution is accurately characterized by the Lou2022 model. The axial crushing properties show that the AA6061-T6 thin-walled rectangular tube undergoes the progressive symmetrical folding deformation mode. The introduction of geometric discontinuity can obviously reduce the peak force and improve the crashworthiness performances under the axial load. The main crushing mode is bending with a small amount of indentation for three-point bending. Moreover, the three-point bending simulation shows that the Lou2022 function considering differential hardening behavior has the highest simulation accuracy. Three different oblique crushing simulations of 10°, 20° and 30° illustrate that the AA6061-T6 rectangular tube at 10° mainly occurs progressive folding deformation. while the other two oblique crushing angles undergo global buckling deformation. The total energy absorption at 10° is 1.87 and 2.43 times of that at 20° and 30°, respectively. The crushing force efficiency of 20° and 30° is 41.28% and 31.8% lower than that of 10°, respectively. A comprehensive understanding of the energy absorption performance of AA6061-T6 thin-walled rectangular tube under different crushing conditions is helpful to determine its position and shape as a vehicle safety structure, and to exert its optimal plastic deformation potential to dissipate the collision energy and ensure passenger safety.本研究通过实验和数值方法研究了 AA6061-T6 薄壁矩形管在轴向挤压、三点弯曲和斜向挤压等不同挤压条件下的能量吸收特性和变形模式。对 AA6061-T6 的四个试样沿不同加载方向进行了单轴拉伸、单轴压缩、剪切和平面应变拉伸的力学试验。此外，通过比较 Lou2022、von Mises 和 SY2009 函数，说明了差异硬化行为对 AA6061-T6 矩形管能量吸收预测的影响。力学实验结果表明，AA6061-T6 表现出明显的各向异性、差异硬化行为和拉伸-压缩不对称，Lou2022 模型准确地描述了其塑性演变过程。轴向挤压性能表明，AA6061-T6 薄壁矩形管经历了渐进对称折叠变形模式。几何不连续性的引入可以明显降低轴向载荷作用下的峰值力，提高耐撞性能。三点弯曲的主要破碎模式为弯曲，并伴有少量压痕。此外，三点弯曲模拟结果表明，考虑差异硬化行为的 Lou2022 函数具有最高的模拟精度。10°、20° 和 30°三种不同的斜压模拟结果表明，AA6061-T6 矩形管在 10° 时主要发生渐进折叠变形，而其他两个斜压角度则发生整体屈曲变形。10° 时的总能量吸收分别是 20° 和 30° 时的 1.87 倍和 2.43 倍。20° 和 30° 的破碎力效率分别比 10° 低 41.28% 和 31.8%。全面了解 AA6061-T6 薄壁矩形管在不同挤压条件下的吸能性能，有助于确定其作为汽车安全结构的定位和形状，发挥其最佳塑性变形潜能，消散碰撞能量，确保乘客安全。Optimizing dimension selection for rain flow counting in fatigue assessment of large-scale lattice wind turbine support structures: a comprehensive study and design guidanceChuannan Xiong, Kaoshan Dai, Yuxiao Luo, Jianze Wangdoi:10.1016/j.tws.2024.112051大型格子式风力机支撑结构疲劳评估中雨流计数尺寸优化选择:综合研究与设计指导The selection of dimension (d) for the rain flow counting matrix significantly influences the reliable prediction of fatigue life in wind turbine support structures. However, there are limited public reports on the impact of dimensions on the fatigue assessment of wind turbine structures. This study explores the influence of dimensions on the fatigue assessment process and outcomes, focusing on a large-scale ultra-high lattice wind turbine support structure from an engineering project. Through integrated load simulation, fatigue load time series for different design load cases (DLCs) are obtained for the overall structure. The rain flow counting method is utilized to derive the overall rain flow counting matrix (Markov_n) with varying dimensions. Subsequently, employing a multi-scale fatigue assessment method, the damage matrix (Markov_D), cumulative fatigue damage (D), and fatigue life are computed. A detailed exploration examines the impact of rain flow counting matrix dimensions on Markov_n, Markov_D, D, fatigue life, and calculation time (t). Furthermore, guidance is provided for selecting the optimal dimension for engineering design. The findings indicate that selecting dimensions that are too small results in the loss and merging of smaller mean and amplitude load values, thereby failing to accurately represent the load history. Moreover, a small dimension yields an excessively cautious estimation of cumulative fatigue damage (D) and underestimates the fatigue life, consequently inflating construction expenses.雨流计数矩阵尺寸（d）的选择对风力涡轮机支撑结构疲劳寿命的可靠预测有很大影响。然而，关于尺寸对风力涡轮机结构疲劳评估影响的公开报道却很有限。本研究以某工程项目中的大型超高格子风力发电机支撑结构为研究对象，探讨了尺寸对疲劳评估过程和结果的影响。通过综合载荷模拟，获得了整体结构在不同设计载荷情况（DLC）下的疲劳载荷时间序列。利用雨流计数法得出了不同维度的整体雨流计数矩阵（Markov_n）。随后，采用多尺度疲劳评估方法，计算出损伤矩阵 (Markov_D)、累积疲劳损伤 (D) 和疲劳寿命。详细探讨了雨流计数矩阵尺寸对 Markov_n、Markov_D、D、疲劳寿命和计算时间 (t) 的影响。此外，还为工程设计选择最佳尺寸提供了指导。研究结果表明，选择过小的维度会导致较小的平均荷载值和振幅荷载值的丢失和合并，从而无法准确表示荷载历史。此外，尺寸过小会导致对累积疲劳损伤（D）的估算过于谨慎，并低估疲劳寿命，从而增加施工成本。Interaction behavior of fixed ended cold-formed steel unequal lipped angle columnsK.C. Kalam Aswathy, M.V. Anil Kumardoi:10.1016/j.tws.2024.112056固定端冷弯型钢不等唇角柱的相互作用特性Studies on post-global flexural–torsional buckling strength and global-global interaction between flexural–torsional and flexural buckling modes in cold-formed steel equal-lipped angle columns have been reported in the literature. Similar global-global interaction involving the first two modes of flexural–torsional buckling in unequal-lipped angles has not yet been explored. In this study, a total of 11 cold-formed unequal lipped angle specimens having two different ranges of ratios of elastic flexural–torsional buckling loads (Pcrft2/Pcrft1 < 3, and Pcrft2/Pcrft1 > 24), indicating high and low interaction of flexural–torsional buckling modes, were tested under axial compression. Additionally, test results from the literature for specimens having 5 < Pcrft2/Pcrft1 < 9 are also used. This is the first study reported in the literature that demonstrates interaction of flexural–torsional modes in cold-formed unequal lipped angle members. All possible interaction between different buckling modes is then systematically studied using the ultimate strength database generated using nonlinear finite element analysis. An interaction equation is proposed based on 36 experimental and 719 numerical data.有关冷弯等边角钢立柱的后全局挠扭屈曲强度和挠扭屈曲模式与挠曲屈曲模式之间的全局-全局相互作用的研究已见诸文献。涉及不等边角钢挠扭屈曲前两种模式的类似全局-全局相互作用尚未得到探讨。在本研究中，共对 11 个冷成形不等边角钢试样进行了轴向压缩测试，这些试样具有两个不同范围的弹性挠曲-扭转屈曲载荷比（Pcrft2/Pcrft1 < 3 和 Pcrft2/Pcrft1 > 24），表明挠曲-扭转屈曲模式的相互作用程度有高有低。此外，还采用了文献中对 5 < Pcrft2/Pcrft1 < 9 的试样的测试结果。这是文献中首次报道冷弯不等边角构件中弯曲-扭转模式相互作用的研究。然后，利用非线性有限元分析生成的极限强度数据库，系统地研究了不同屈曲模式之间所有可能的相互作用。根据 36 个实验数据和 719 个数值数据，提出了一个相互作用方程。Advances in resin matrix composite fan blades for aircraft engines: A reviewJiahui Wei, Yifan Zhang, Yanfeng Liu, Yuansong Wang, Chao Li, Zheng Sun, Hongming Xu, Hongyan Shao, Daijun Zhang, Qi Zou, Qian Zhang, Jiading Feng, Weiyi Kong, Yanan Jiao, Li Chendoi:10.1016/j.tws.2024.112058航空发动机用树脂基复合材料风扇叶片研究进展In the past few decades, the development of aircraft engines has targeted high bypass ratios and lightweight construction. The use of lighter and larger fan blades can facilitate the technical requirements of engine weight reduction with an increased bypass ratio, achieving improved engine operating efficiency and performance. The current literature has established that resin matrix composite fan blades (RMCFBs), as an alternative to traditional lightweight metal fan blades, exhibit high energy absorption efficiency and a stable response curve. This review assesses the latest research progress in the development and application of RMCFBs for aircraft engines. Firstly, the characteristics of different manufacturing processes are established with a classification of RMCFBs. Current application status of RMCFBs is discussed, evaluating the progress that has been made in specific systems. The pertinent experimental tests and numerical simulations applied to mechanical performance of RMCFBs at different levels are reviewed in detail, taking account of the defects in RMCFBs with consideration of non-destructive testing and the on-line monitoring technologies that have been employed. Finally, the current key research issues are identified, and future directions are proposed. This review can serve as a valuable reference that establishes current state-of-the-art in the design and development of RMCFBs for aircraft engine.在过去的几十年里，航空发动机的发展目标是高涵道比和轻量化结构。采用更轻、更大的风扇叶片，可以满足发动机减重的技术要求，增加涵道比，提高发动机的工作效率和性能。目前已有文献表明，树脂基复合材料风扇叶片(RMCFBs)作为传统轻质金属风扇叶片的替代品，具有较高的能量吸收效率和稳定的响应曲线。本文综述了航空发动机用rmcfb的最新研究进展。首先，对rmcfb进行分类，建立了不同制造工艺的特征。讨论了rmcfb的应用现状，评价了在具体系统中取得的进展。考虑到rmcfb存在的缺陷，结合现有的无损检测和在线监测技术，对不同水平rmcfb力学性能的相关实验测试和数值模拟进行了详细的综述。最后，指出了当前的重点研究问题，并提出了未来的研究方向。该综述可为建立当前航空发动机rmcfb的设计和开发水平提供有价值的参考。来源：复合材料力学仿真Composites FEM
