【新文速递】2024年10月12日固体力学SCI期刊最新文章

 

今日更新：International Journal of Solids and Structures 4 篇，Journal of the Mechanics and Physics of Solids 4 篇，Mechanics of Materials 1 篇，International Journal of Plasticity 2 篇，Thin-Walled Structures 2 篇

International Journal of Solids and Structures

Three-dimensional elastic–plastic lattice-spring model based on sapphire crystal structure and its application to impact characterisation studies

Yongqiang Li

doi:10.1016/j.ijsolstr.2024.113097

基于蓝宝石晶体结构的三维弹塑性点阵弹簧模型及其在冲击表征研究中的应用

A thirteen-node octahedral three-dimensional lattice-spring model based on the sapphire crystal structure is established by applying the parameter mapping theory, and the finite element stiffness matrix is mapped into the linear spring stiffness coefficients of the lattice-spring model according to the parameter mapping method, so that the selection of the spring stiffness coefficients has a strict mathematical derivation. The elastic–plastic potential function that unifies the elastic–plastic characteristics of the material and the fracture energy is established. The lattice-spring model is tested by three algorithms, including longitudinal wave velocity, three-dimensional crack extension path under dynamic indentation, and impact compression deformation and lattice size sensitivity test, and the test results show that the established three-dimensional lattice-spring model has a high computational accuracy. The correctness of the calculation of the lattice-spring model is verified by comparing the calculation of the evolution process of spherical impact damage on the edge of sapphire under different crystal directions with the experiment.

应用参数映射理论，建立了基于蓝宝石晶体结构的十三节点八面体三维点阵弹簧模型，并根据参数映射法将有限元刚度矩阵映射为点阵弹簧模型的线性弹簧刚度系数，从而对弹簧刚度系数的选取进行了严格的数学推导。建立了材料弹塑性特性与断裂能相统一的弹塑性势函数。采用纵波速度、动态压痕下三维裂纹扩展路径、冲击压缩变形和点阵尺寸敏感性试验三种算法对网格弹簧模型进行了测试，测试结果表明所建立的三维网格弹簧模型具有较高的计算精度。通过对蓝宝石在不同晶向下边缘球面冲击损伤演化过程的计算与实验的对比，验证了晶格-弹簧模型计算的正确性。

Elastic wave propagation in periodic stress-driven nonlocal Timoshenko beams

Gioacchino Alotta, Andrea Francesco Russillo, Giuseppe Failla

doi:10.1016/j.ijsolstr.2024.113103

周期性应力驱动非局部Timoshenko梁中的弹性波传播

Nonlocal theories are well established to model statics and dynamics of small-size structures. Recent studies investigated elastic wave propagation in nonlocal beams and attention focused on periodic nonlocal beams, either endowed with resonators or resting on supports, for relevant applications at small scale. In this context, this work proposes a stress-driven nonlocal Timoshenko beam formulation and develops an original and comprehensive analytical/computational framework for wave propagation analysis in bare and periodic beams. The framework addresses infinite and finite beams. First, exact analytical expressions are derived for the dispersion curves of the bare beam, which provide full insight into the effects of nonlocality. Second, an exact Plane Wave Expansion method is devised for periodic beams, either equipped with mass–spring resonators or resting on elastic supports; both ω ( q ) and q ( ω ) dispersion curves are derived in this work, where ω is the frequency and q is the wave number. Third, an approximate homogenization approach is formulated to estimate opening frequencies and sizes of band gaps induced by mass–spring resonators. Finally, a two-field finite element method is proposed to calculate the transmittance of finite periodic beams. Numerical applications investigate the band structure of bare and periodic beams for different internal lengths of the stress-driven nonlocal model. Remarkably, results for finite periodic beams validate the predictions from wave propagation analysis of corresponding infinite ones. Moreover, parametric analyses show the capability of the stress-driven nonlocal model in capturing typical small-size effects.

非局部理论已经很好地建立了小尺寸结构的静力学和动力学模型。近年来对弹性波在非局部梁中的传播进行了研究，重点研究了具有谐振腔或支承的周期性非局部梁在小尺度上的相关应用。在此背景下，本工作提出了应力驱动的非局部Timoshenko梁公式，并开发了一个原始和全面的分析/计算框架，用于裸梁和周期梁的波传播分析。框架处理无限和有限梁。首先，导出了裸光束色散曲线的精确解析表达式，充分揭示了非定域性的影响。其次，设计了具有质量弹簧谐振器和弹性支承的周期梁的精确平面波展开方法；本文导出了ω (q)和q （ω）色散曲线，其中ω为频率，q为波数。第三，提出了一种近似均匀化的方法来估计质量弹簧谐振器引起的带隙的打开频率和大小。最后，提出了一种计算有限周期光束透过率的双场有限元方法。数值应用研究了应力驱动非局部模型不同内长度下裸梁和周期梁的能带结构。值得注意的是，有限周期梁的结果验证了相应无限周期梁的波传播分析的预测。此外，参数分析表明应力驱动的非局部模型能够捕获典型的小尺寸效应。

A metamaterial with sign-switching and discontinuous Poisson’s ratio

Teik-Cheng Lim

doi:10.1016/j.ijsolstr.2024.113095

具有符号切换和不连续泊松比的超材料

The fragmentation-reconstitution (FR) metamaterial has recently been shown to be a suitable candidate for producing Poisson’s ratio discontinuity at the original state. A new FR metamaterial is introduced herein that additionally permits sign-switching of Poisson’s ratio upon stress reversal along one axis. This was achieved by the use of rotating rhombi in which every rhombus can be further fragmented into six sub-units. The latter consists of two non-rotating smaller rhombi and four rotating isosceles triangles. While results show that the metamaterial exhibits sign-switching of Poisson’s ratio upon stress reversal along one axis due to differing mechanism, this is not so for loading in then other on-axis direction due to the dimension being maximum in that direction. Instead, there are two compression pathways which can lead to either fragmentation or reconstitution modes of deformation. The predisposition for each pathway is proposed by means of charge attachments. The uniqueness of this metamaterial avails its use for applications that are not attainable by other materials and metamaterials.

断裂-重构(FR)超材料最近被证明是在原始状态下产生泊松比不连续的合适候选材料。本文介绍了一种新的FR超材料，该材料在应力沿一轴反转时允许泊松比的符号切换。这是通过使用旋转菱形来实现的，其中每个菱形可以进一步破碎成六个亚单位。后者由两个不旋转的小菱形和四个旋转的等腰三角形组成。结果表明，由于不同的机制，在应力沿一个轴方向反转时，超材料的泊松比表现出符号转换，而在另一个轴向加载时，由于尺寸在该方向最大，所以这种情况不会发生。相反，有两种压缩途径可以导致变形的破碎或重构模式。通过电荷附着物的方法，提出了各通路的易感性。这种超材料的独特性使其应用于其他材料和超材料无法实现的应用。

A force-density framework for flexible multi-body dynamic analysis of clustered tensegrity structures

Qing Lv, Yaqiong Tang, Xuechi Wang, Tuanjie Li

doi:10.1016/j.ijsolstr.2024.113098

聚类张拉整体结构柔性多体动力分析的力密度框架

This paper develops a versatile and effective force-density framework for the flexible multi-body dynamic analysis of clustered tensegrity structures. In this framework, the force density is selected as the basic variable instead of force, and the clustered tensegrity structure is mathematically described in a vector and matrix form, encompassing topology, geometry, material, and force properties. A non-negative variable is defined as an indicator of the member stress state, and a complementary function is constructed to address the discontinuity issues that arise from the unidirectional axial stiffness of cables. Dynamic formulas are established within this force-density framework, with nodal coordinates selected as generalized parameters and formulations constructed in a matrix form. A complementary framework is established as an alternative for solving the dynamic equations, transforming the isolated steps of Newton’s iteration and cable state judgment (slack or tension) into a unified one, bringing more potential for improving solving efficiency. Numerical simulations are carried out to validate the approach, demonstrating that it effectively reveals the dynamic oscillation, tension changes, and cable slack behavior of clustered tensegrity structures during shape control. Comparative studies highlight the advantage of computational efficiency. The method proposed in this paper provides a robust mathematical model for studying clustered tensegrity structures, particularly regarding the shape control of deployable, active, and intelligent structures, aiding in understanding dynamic oscillation, tension changes, and cable slack behavior during their deformation. The methods can also be applied to cable net structures and other prestressed pin-jointed systems.

本文开发了一种通用的、有效的力密度框架，用于聚类张拉整体结构的柔性多体动力分析。在该框架中，力密度被选择为基本变量，而不是力，聚类张拉整体结构以矢量和矩阵形式进行数学描述，包括拓扑、几何、材料和力特性。定义了一个非负变量作为构件应力状态的指标，并构建了一个互补函数来解决由电缆单向轴向刚度引起的不连续问题。在此力-密度框架内建立动力公式，选取节点坐标作为广义参数，以矩阵形式构造公式。建立了一个互补框架作为求解动力学方程的备选方案，将牛顿迭代和索状态判断(松弛或张力)的孤立步骤统一起来，为提高求解效率带来了更大的潜力。数值仿真验证了该方法的有效性，结果表明该方法能有效地揭示出簇状张拉整体结构在形状控制过程中的动态振荡、张力变化和索松弛行为。比较研究突出了计算效率的优势。本文提出的方法为研究簇状张拉整体结构提供了一个鲁棒的数学模型，特别是关于可展开、主动和智能结构的形状控制，有助于理解其变形过程中的动态振荡、张力变化和索松弛行为。该方法也可应用于索网结构和其他预应力铰缝体系。

Journal of the Mechanics and Physics of Solids

Residual stress development in lattice mismatched epitaxial thin films via atomic and molecular layer depositions

Musanna Galib, Okan K. Orhan, Jian Liu, Mauricio Ponga

doi:10.1016/j.jmps.2024.105897

通过原子和分子层沉积晶格错配外延薄膜的残余应力发展

Atomic and molecular layer deposition (ALD/MLD) coatings are promising solutions for preventing dendrite formation in aqueous and non-aqueous Li/Na/Zn metal batteries. Notably, alumina and alucone coatings have emerged as highly effective against dendrite formation in Zn anodes. Despite their demonstrated efficacy, a comprehensive understanding of their chemo-mechanical impact on anodes remains elusive. In this study, we take a bottom-up framework to these coatings on Zn foils, employing an approach that integrates ab initio simulations with continuum theories to elucidate lattice misfit and chemical bonding. We use this insight to develop a macroscopic model to predict the epitaxial residual stresses generated during thin-film deposition. Our findings reveal a robust chemical bonding between the hydroxylated Zn surface and the thin film. This, in turn, generates large misfit strains that result in significant interfacial stresses during deposition. These results are then compared to experiments by measuring the curvature of the coated thin films, finding good agreement between experiments and theory. This novel understanding sheds light on the fundamental mechanisms underpinning the development of chemo-mechanical stresses in thin films, which impact dendrite suppression in anodes, offering valuable insights for the design of new coatings.

原子和分子层沉积(ALD/MLD)涂层是防止水/非水Li/Na/Zn金属电池枝晶形成的有前途的解决方案。值得注意的是，氧化铝和铝酮涂层在防止锌阳极枝晶形成方面非常有效。尽管它们已被证明有效，但对它们对阳极的化学-机械影响的全面理解仍然难以捉摸。在这项研究中，我们采用自下而上的框架来研究锌箔上的这些涂层，采用一种将从头算模拟与连续介质理论相结合的方法来阐明晶格错配和化学键合。我们利用这一见解开发了一个宏观模型来预测薄膜沉积过程中产生的外延残余应力。我们的发现揭示了羟基化锌表面和薄膜之间的强大的化学键。这反过来又会产生较大的错配应变，从而在沉积过程中产生显著的界面应力。然后，通过测量涂层薄膜的曲率，将这些结果与实验结果进行比较，发现实验结果与理论结果很吻合。这一新颖的理解揭示了薄膜中化学机械应力发展的基本机制，它影响阳极中枝晶的抑制，为新涂层的设计提供了有价值的见解。

Progressive failure analysis of laminates with an open-hole subjected to compressive loading (OHC) using the enhanced semi-discrete modeling framework

Vignesh Shankar Iyer, Minh Hoang Nguyen, Royan J. D’Mello, Anthony M. Waas

doi:10.1016/j.jmps.2024.105902

基于改进半离散模型框架的开孔层压板在压缩载荷作用下的渐进失效分析

The Open-hole compressive (OHC) strength of a fiber reinforced laminate is one of the most critical allowables for design of aerostructures. In this paper, results for predicting the OHC strength using the semi-discrete damage modeling framework are presented. The predictions are seen to capture experimentally observed failure mechanisms and measured failure loads. The constitutive model includes local axial compressive failure (and subsequent load bearing at a reduced plateau stress) while maintaining numerical robustness. Standard stacking sequences (quasi-isotropic, “hard” and “soft”) have been analyzed and compared to publicly available databases. Additionally, the model is challenged to predict delamination-dominated failure due to ply-scaling. Overall, the model is able to capture relevant failure mechanisms, while the ultimate loads are predicted with good accuracy. Therefore, this framework can be used with confidence in predicting OHC strengths of laminates.

纤维增强层压板的开孔抗压强度是航空结构设计中最关键的允许值之一。本文给出了用半离散损伤模型框架预测热固强度的结果。预测被视为捕获实验观察到的失效机制和测量的失效载荷。本构模型包括局部轴向压缩破坏（以及随后在降低高原应力下的承载），同时保持数值鲁棒性。标准堆叠序列(准各向同性，“硬”和“软”)已被分析并与公开可用的数据库进行比较。此外，该模型还面临着预测由层序缩放引起的分层主导失效的挑战。总体而言，该模型能够捕捉到相关的破坏机制，同时对极限荷载的预测精度较高。因此，该框架可用于预测层压板的热盐强度。

Crystallographically programmed kirigami metamaterials

Ruoqi He, Yao Chen, Jingbing Liang, Yue Sun, Jian Feng, Pooya Sareh

doi:10.1016/j.jmps.2024.105903

晶体学编程的基利伽米超材料

In recent years, lattice kirigami metamaterials have attracted considerable attention due to their unconventional and often intriguing mechanical properties. However, the absence of a comprehensive analytical framework has hindered advancements in both research and practical applications. Here, we introduce an integrated framework that enables the customization, form-finding, analysis, and manufacturing of polygonal lattice kirigami metamaterials (PLKMs). By employing a strain-energy-based method, we derive the effective mechanical properties of these systems and demonstrate that structural design is an effective strategy for tailoring these properties. Additionally, we introduce a group-theory-based method for generating crystallographic kirigami metamaterials through selective symmetry breaking, complemented by lattice theory to capture and program their structural characteristics. An automated workflow is also developed for modeling, analysis, and manufacturing of these metamaterials, followed by an image-processing-based design algorithm for composite PLKMs. To illustrate the capabilities of the proposed integrated framework, we explore its potential in driving innovative applications for PLKMs. It is anticipated that this work will provide valuable insights into potential innovations in kirigami metamaterial research and engineering.

近年来，晶格基叠米超材料因其非常规和有趣的力学性能而引起了人们的广泛关注。然而，缺乏一个全面的分析框架阻碍了研究和实际应用的进展。在这里，我们介绍了一个集成的框架，使定制，形式查找，分析和制造多边形晶格基利伽米超材料(plkm)成为可能。通过采用基于应变能的方法，我们得出了这些系统的有效力学性能，并证明了结构设计是定制这些性能的有效策略。此外，我们介绍了一种基于群论的方法，通过选择性对称破缺来生成晶体基里伽米超材料，并辅以晶格理论来捕获和编程其结构特征。此外，还开发了用于建模、分析和制造这些超材料的自动化工作流程，然后是基于图像处理的复合plkm设计算法。为了说明所提出的集成框架的能力，我们探讨了其在推动plkm创新应用方面的潜力。预计这项工作将为基利美超材料研究和工程的潜在创新提供有价值的见解。

Relation of synthesis and fatigue property in elastic soft materials

Yecheng Wang, Danqi Sun

doi:10.1016/j.jmps.2024.105894

弹性软材料的合成与疲劳性能的关系

Fatigue has long been studied for many materials, but many aspects are not well understood. Our recent study of the distinct roles of crosslinks and entanglements in the synthesis-property relation of a polymer network under monotonic load leads to a fundamental question: how do crosslinks and entanglements affect the synthesis-property relation of a polymer network under cyclic load? Here we study the relation of synthesis and fatigue property of elastic soft materials without precut cracks. We prepare polyacrylamide hydrogels by free radical polymerization as a model system, and swell the hydrogels in water to equilibrium or to a certain amount of polymer content. The synthesis parameters include the crosslinker-to-monomer molar ratio and the water-to-monomer molar ratio in the precursor, as well as the polymer content in the hydrogel. Three series of hydrogels are prepared. For each hydrogel, the stress-stretch curve under cyclic stretch of various amplitudes and the number of cycles to rupture are measured, giving four properties: fatigue life, endurance stretch, endurance stress, and endurance work. When the crosslinker-to-monomer molar ratio in the precursor is high, the degree of network imperfection on average is low. When the water-to-monomer molar ratio in the precursor is low, the number of entanglements per polymer segment on average is large. We show that crosslinks decrease the susceptibility to fatigue and entanglements increase the endurance stress. By contrast, both crosslinks and entanglements negligibly affect the endurance stretch and the endurance work.

长期以来，人们对许多材料的疲劳进行了研究，但许多方面还没有得到很好的理解。我们最近对单调负载下聚合物网络的合成-性能关系中交联和缠结的不同作用的研究导致了一个基本问题:交联和缠结如何影响循环负载下聚合物网络的合成-性能关系?本文研究了无预切裂纹弹性软材料的合成与疲劳性能的关系。以自由基聚合法制备聚丙烯酰胺水凝胶为模型体系，将水凝胶在水中膨胀至平衡状态或达到一定的聚合物含量。合成参数包括前驱体中交联剂与单体的摩尔比、水与单体的摩尔比以及水凝胶中的聚合物含量。制备了三个系列的水凝胶。对每种水凝胶，测量其在不同幅值的循环拉伸下的应力-拉伸曲线和断裂的循环次数，得出其疲劳寿命、持久拉伸、持久应力和持久功四项性能。当前驱体中交联剂与单体的摩尔比较高时，网络不完善程度平均较低。前驱体中水单体摩尔比较低时，平均每个聚合物段的缠结数较大。我们发现交联降低了对疲劳的敏感性，而缠结增加了耐力应力。相比之下，交联和缠结对持久拉伸和持久功的影响可以忽略不计。

Mechanics of Materials

Influence of Shot-Peening on the Self-Heating Behavior and Fatigue Properties of 300M Steel

Pierrick Lepitre, Louis-Maël Merlet, Cédric Doudard, Matthieu Dhondt, Martin Surand, Sylvain Calloch

doi:10.1016/j.mechmat.2024.105174

喷丸强化对300M钢自热性能和疲劳性能的影响

Shot peening is an established cold working process used to introduce residual compressive stresses on a surface and is extensively studied using conventional fatigue tests. However, it has not been widely studied using the self-heating method. Specifically, the heterogeneity of the dissipation field has not been estimated, with only an average approach being used. Previous investigations in the case of 300M steel demonstrated that the effect of shot peening on the high cycle fatigue properties can be either beneficial or detrimental. This study proposes to apply the self-heating method on polished 300M and to investigate the effect of mean stress and shot peening on the dissipation behavior. A modified self-heating model is proposed and calibrated for 300M steel. Combined with residual stress profiles, a method to compute and determine the shot peening effect on self-heating behavior through single point surface measurements is proposed. Application on 300M steel shows excellent results, the over-dissipation being mainly due to the sub-surface compressive residual stresses. The self-heating method has proven useful to quickly estimate fatigue properties of polished 300M steel. Based on the understanding of the self-heating curve of shot peened 300M steel, a quantification of shot-peening effect on fatigue limit is discussed.

喷丸强化是一种成熟的冷加工工艺，用于在表面上引入残余压应力，并通过常规疲劳试验进行了广泛的研究。然而，利用自加热方法对其进行的研究并不广泛。具体来说，耗散场的非均质性没有得到估计，只采用了平均方法。先前对300M钢的研究表明，喷丸强化对高周疲劳性能的影响可能是有益的，也可能是有害的。本研究拟将自热法应用于抛光后的300M，研究平均应力和喷丸对其耗散行为的影响。提出了一种改进的300M钢自热模型，并对其进行了标定。结合残余应力分布，提出了一种通过单点表面测量来计算和确定喷丸强化对自热性能影响的方法。在300M钢上的应用取得了良好的效果，超耗散主要是由于次表面压残余应力。实验证明，自热法可以快速测定抛光后300M钢的疲劳性能。在了解喷丸强化300M钢自热曲线的基础上，探讨了喷丸强化对疲劳极限影响的量化。

International Journal of Plasticity

Enhancing the ductility and yield strength of 2.7Mn steel via two-step partitioning heat treatment

Wenlu Yu, Lihe Qian, Chaozhang Wei, Kaifang Li, Yipeng Ding, Pengfei Yu, Zhixuan Jia, Fucheng Zhang, Jiangying Meng

doi:10.1016/j.ijplas.2024.104148

通过两步分割热处理提高2.7Mn钢的塑性和屈服强度

Fresh martensite (FM) is often present in medium-Mn steels, especially when containing lower Mn content, due to the insufficient thermal stability of reverted austenite; this FM is brittle, largely deteriorating the ductility. In this paper, large ductility and high yield strength are achieved in an Al/Si-added medium-Mn steel containing 2.7Mn via a two-step partitioning heat treatment, i.e. intercritical annealing (IA) followed by low-temperature partitioning (LTP). We show that, during the IA, C and Mn atoms partition from the pre-quenched martensite to reverted austenite; Al addition reduces the size of reverted austenite and promotes C and Mn enrichment in the reverted austenite by decelerating its growth kinetics. This enables the reverted austenite more thermally stabilized, thereby reducing the amount of FM and increasing the amount and mechanical stability of retained austenite (RA) at room temperature. During the LTP, accompanied with the recovery of dislocations and the suppression of carbide precipitation by Al and Si, C atoms further partition from FM to RA, which enables the RA more mechanically stabilized and thereby sustains the high strain hardening to larger strains. Simultaneously, the FM becomes less hard and less brittle due to C atoms depletion and dislocations recovery, alleviating the stress/strain localization and favoring the uniform plastic deformation. Furthermore, the decrease in mobile dislocation density that is accompanied with the recovery of dislocations is believed to be mainly responsible for the enhanced yield strength of the steel. The present results indicate that the synergetic effects of the primary element partitioning (promoted by Al) during IA, which increases the thermal stability of reverted austenite, and the secondary element partitioning (enhanced by Al and Si) and as well dislocation recovery during LTP, which increases the mechanical stability of RA and the uniformity of plastic deformation, significantly enhance both the ductility and yield strength of medium-Mn steel with low Mn content.

由于还原奥氏体的热稳定性不足，新鲜马氏体(FM)经常存在于中Mn钢中，特别是当Mn含量较低时;这种FM是脆的，很大程度上恶化了延展性。本文采用临界间退火（IA）和低温配分（LTP）两步配分热处理方法，对含有2.7Mn的Al/ si中mn钢进行了大塑性和高屈服强度的制备。结果表明，在IA、C和Mn原子从预淬火马氏体向还原奥氏体分离的过程中;Al的加入降低了还原奥氏体的尺寸，并通过减缓其生长动力学来促进C和Mn在还原奥氏体中的富集。这使得还原奥氏体更加热稳定，从而减少了FM的数量，增加了室温下残留奥氏体(RA)的数量和机械稳定性。在LTP过程中，随着位错的恢复以及Al和Si对碳化物析出的抑制，C原子进一步从FM向RA分异，使RA更加机械稳定，从而维持了高应变硬化到更大应变。同时，由于C原子的损耗和位错的恢复，FM的硬度和脆性降低，减轻了应力/应变局部化，有利于均匀的塑性变形。此外，随着位错的恢复，可移动位错密度的降低被认为是钢屈服强度提高的主要原因。研究结果表明:低锰中锰钢的塑性和屈服强度均得到了显著提高，IA过程中由Al促进的初生元素分配提高了还原奥氏体的热稳定性，LTP过程中由Al和Si促进的次生元素分配和位错恢复提高了RA的力学稳定性和塑性变形的均匀性。

The interactions of deformation twins, zirconium hydrides, and microcracks

Saiedeh Marashi, Hamidreza Abdolvand

doi:10.1016/j.ijplas.2024.104149

变形孪晶、氢化锆与微裂纹的相互作用

One of the main degradation mechanisms of the zirconium alloys used in nuclear reactors is hydrogen embrittlement and the formation of zirconium hydrides. This study focuses on understanding the interactions among deformation twins, hydrides, and the microcracks that form within hydrides. For this purpose, in-situ scanning electron microscopy and interrupted ex-situ tensile experiments were conducted on hydrided zirconium specimens with favorable initial textures for the formation of extension twins. Electron backscatter diffraction (EBSD) was used to measure the orientations of the grains located in the specimens’ gauges and map them into a crystal plasticity finite element model to study hydrides and twins interactions. High spatial resolution EBSD and high-resolution imaging were used to follow the formation of microcracks, and twins live. Although the specimens were deformed to a moderate level of applied strain (∼7%), it was observed that two types of twins nucleate, { 10 1 ¯ 2 } and { 11 2 ¯ 1 } . While the former nucleates either before or after the nucleation of microcracks within hydrides, the latter nucleates after the formation of microcracks and grows with them. It is shown that the formation of twins may contribute to crack nucleation, yet the shear energy density on a given slip system within hydrides is the main driving force for crack nucleation. Regardless of hydride interactions with twins, a significant slip activity is recorded within hydrides prior to cracking.

核反应堆用锆合金的主要降解机制之一是氢脆和氢化锆的形成。本研究的重点是了解变形孪晶、氢化物和氢化物内部形成的微裂纹之间的相互作用。为此，对初始织构有利于扩展孪晶形成的氢化锆试样进行了原位扫描电镜和间断异地拉伸实验。利用电子后向散射衍射（EBSD）测量了试样量规中晶粒的取向，并将其映射到晶体塑性有限元模型中，以研究氢化物和孪晶的相互作用。采用高空间分辨率EBSD和高分辨率成像技术跟踪微裂纹的形成。虽然试样变形到中等水平的施加应变(~ 7%)，但观察到两种类型的孪核，{10.1¯2}和{11.2¯1}。前者在氢化物内部微裂纹成核之前或之后成核，后者在微裂纹形成之后成核并随微裂纹一起长大。结果表明，孪晶的形成可能有助于裂纹形核，但在给定的滑移体系中，氢化物内部的剪切能密度是裂纹形核的主要驱动力。不管氢化物与孪晶的相互作用如何，在开裂之前，在氢化物内部记录了显著的滑移活动。

Thin-Walled Structures

Flexural behavior and design of cold-formed steel gapped back-to-back built-up beams with discontinuous connecting plates

Liping Wang, Mahmud B. Dawud, Yancheng Cai

doi:10.1016/j.tws.2024.112548

带不连续连接板的冷弯型钢间隙背靠背组合梁的受弯性能与设计

This paper investigates the flexural behavior of a new type of cold-formed steel gapped back-to-back built-up beams, which are joined using discontinuous connecting plates and bolts under four-point bending. A finite element model was developed and validated against experimental results from the literature, focusing on ultimate moments, moment-curvature curves, and failure modes. Following successful validation, the model was used for an extensive parametric study to examine the impact of key parameters on the flexural behavior of the built-up beams. These parameters include bolt arrangement on each connecting plate, the ratio of connecting plate spacing to web depth, cross-sectional dimensions, the gap between the built-up channels, and beam length. The primary failure mode observed was lateral torsional buckling. The ultimate strengths obtained from the finite element analysis were compared with the nominal strengths predicted by the Direct Strength Method (DSM) specified in the American Specification. It was found that the DSM predictions were generally conservative. Consequently, a modified DSM equation was proposed. Comparisons with numerical results demonstrated that the modified DSM equation provided more accurate strength predictions than the current DSM. Reliability analysis confirmed the dependability of the modified DSM predictions, leading to the recommendation of the modified DSM for designing cold-formed steel gapped back-to-back built-up beams joined via discontinuous connecting plates and bolts.

本文研究了一种采用不连续连接板和螺栓连接的新型冷弯型钢缝隙背靠背组合梁在四点弯曲作用下的抗弯性能。建立了一个有限元模型，并根据文献中的实验结果进行了验证，重点关注极限弯矩、弯矩-曲率曲线和破坏模式。在成功验证之后，该模型被用于广泛的参数研究，以检查关键参数对组合梁的弯曲行为的影响。这些参数包括每个连接板上的螺栓布置、连接板间距与腹板深度的比率、截面尺寸、已建通道之间的间隙以及梁的长度。观察到的主要破坏模式是侧向扭转屈曲。将有限元分析得到的极限强度与美国规范中直接强度法(DSM)预测的标称强度进行了比较。人们发现，DSM的预测总体上是保守的。据此，提出了修正后的DSM方程。与数值结果的比较表明，修正后的DSM方程比现有的DSM方程提供了更准确的强度预测。可靠性分析证实了改进后的DSM预测的可靠性，从而推荐将改进后的DSM用于设计通过不连续连接板和螺栓连接的冷弯型钢间隙背靠背组合梁。

In-plane crushing behavior and energy absorption of CFRP honeycombs with different core topologies

Levent Pehlivan, Cengiz Baykasoğlu

doi:10.1016/j.tws.2024.112566

不同芯型CFRP蜂窝的面内破碎性能及吸能特性

The in-plane crushing behavior and energy absorption performance of carbon fiber reinforced polymer (CFRP) honeycombs with different core topologies were experimentally investigated under uniaxial loading conditions. Three types of CFRP honeycomb core topologies (i.e. circular, square and hexagonal) with different cell wall thicknesses and heights were considered in the designs. The honeycomb samples were fabricated by the molding and bonding process, which is widely used in the easy, fast and economical manufacturing of thin-walled honeycomb structures. A total of twenty-seven sample groups were experimentally tested for each loading condition, in which honeycomb samples with different core topologies were designed to have almost the same weights for a meaningful comparison. The experimental results revealed that all honeycomb designs have higher in-plane compression strength in the expansion direction, and hexagonal honeycombs showed the highest strength and energy absorption performance in both directions due to their stable load-carrying capacity and outstanding force efficiency. In particular, the experimental findings showed that the crushing strength and the specific energy absorption of CFRP honeycomb structures can be improved up to 6.1 and 4.2 times, respectively, by properly adjusting the cell wall thickness and height parameters. The results also revealed that the proposed lightweight CFRP honeycombs with the structural densities of 155-283 kg/m3 showed better in-plane crushing performance than many competing cellular topologies.

对碳纤维增强聚合物（CFRP）蜂窝在单轴载荷条件下的面内破碎行为和吸能性能进行了实验研究。设计中考虑了三种不同细胞壁厚度和高度的CFRP蜂窝芯拓扑结构（即圆形、方形和六边形）。采用模压-粘接工艺制备蜂窝样品，该方法易于、快速、经济地制造薄壁蜂窝结构。在每种加载条件下，共有27组样本进行了实验测试，其中具有不同核心拓扑结构的蜂窝样本被设计为具有几乎相同的权重，以便进行有意义的比较。实验结果表明，所有蜂窝设计在膨胀方向上都具有较高的面内抗压强度，其中六角形蜂窝由于其稳定的承载能力和突出的力效率，在两个方向上都表现出最高的强度和吸能性能。实验结果表明，通过适当调整蜂窝壁厚和高度参数，CFRP蜂窝结构的抗压强度和比能吸收率分别可提高6.1倍和4.2倍。结果还表明，结构密度为155-283 kg/m3的轻质CFRP蜂窝比许多竞争的蜂窝拓扑具有更好的面内破碎性能。