【新文速递】2023年11月2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 1 篇，Thin-Walled Structures 8 篇

International Journal of Solids and Structures

Propagation mechanism of low-frequency elastic waves and vibrations in a new tetragonal hybrid metamaterial

Yang Hong-yun, Cheng Shu-liang, Li Xiao-feng, Yan Qun, Wang Bin, Xin Ya-jun, Sun Yong-tao, Ding Qian, Yan Hao, Zhao Qing-xin

doi:10.1016/j.ijsolstr.2023.112536

新型四方混合超材料中低频弹性波和振动的传播机理

In order to achieve low-frequency vibration and noise reduction, artificial metamaterial with great potential in this field have been widely found. Based on previous studies, a new tetragonal hybrid metamaterial structure is proposed in this paper. It is exciting that the combination of inclusions with different material properties and sizes can affect the generation of band gaps. Then, based on the selected frequency, the propagation characteristics of waves in the structure were qualitatively analyzed using group velocity and phase velocity, and the potential for vibration reduction and noise reduction of the proposed structure was verified through finite element simulation of vibration in finite period structures. The results show that the proposed structure can open multiple broadband gaps, and the frequency range of the band gap can be flexibly adjusted according to needs. This study provides a new way for the design of low-frequency phononic metamaterial systems.

为了实现低频减振降噪，在这一领域具有巨大潜力的人工超材料被广泛发现。在以往研究的基础上，本文提出了一种新的四方混合超材料结构。令人兴奋的是，不同材料特性和尺寸的夹杂物组合会影响带隙的产生。然后，根据所选频率，利用群速度和相速度定性分析了波在结构中的传播特性，并通过有限周期结构振动的有限元模拟验证了所提结构的减振降噪潜力。结果表明，所提出的结构可以打开多个宽带隙，带隙的频率范围可以根据需要灵活调整。这项研究为低频声子超材料系统的设计提供了一条新途径。

A graph-based probabilistic geometric deep learning framework with online enforcement of physical constraints to predict the criticality of defects in porous materials

Krokos Vasilis, Bordas Stéphane P.A., Kerfriden Pierre

doi:10.1016/j.ijsolstr.2023.112545

基于图的概率几何深度学习框架，在线执行物理约束，预测多孔材料缺陷的临界度

Stress prediction in porous materials and structures is challenging due to the high computational cost associated with direct numerical simulations. Convolutional Neural Network (CNN) based architectures have recently been proposed as surrogates to approximate and extrapolate the solution of such multiscale simulations. These methodologies are usually limited to 2D problems due to the high computational cost of 3D voxel based CNNs. We propose a novel geometric learning approach based on a Graph Neural Network (GNN) that efficiently deals with three-dimensional problems by performing convolutions over 2D surfaces only. Following our previous developments using pixel-based CNN, we train the GNN to automatically add local fine-scale stress corrections to an inexpensively computed coarse stress prediction in the porous structure of interest. Our method is Bayesian and generates densities of stress fields, from which credible intervals may be extracted. As a second scientific contribution, we propose to improve the extrapolation ability of our network by deploying a strategy of online physics-based corrections. Specifically, we condition the posterior predictions of our probabilistic predictions to satisfy partial equilibrium at the microscale, at the inference stage. This is done using an Ensemble Kalman algorithm, to ensure tractability of the Bayesian conditioning operation. We show that this innovative methodology allows us to alleviate the effect of undesirable biases observed in the outputs of the uncorrected GNN, and improves the accuracy of the predictions in general.

由于直接数值模拟的计算成本较高，多孔材料和结构的应力预测具有挑战性。最近提出了基于卷积神经网络（CNN）的架构，作为近似和推断此类多尺度模拟解决方案的替代方案。由于基于三维体素的 CNN 计算成本较高，这些方法通常仅限于二维问题。我们提出了一种基于图神经网络（GNN）的新型几何学习方法，只需对二维表面进行卷积，即可高效处理三维问题。根据我们之前使用基于像素的 CNN 所取得的进展，我们对 GNN 进行了训练，以自动将局部细尺度应力修正添加到相关多孔结构中廉价计算的粗应力预测中。我们的方法是贝叶斯法，可生成应力场密度，并从中提取可信区间。作为第二个科学贡献，我们建议通过部署基于物理的在线修正策略来提高我们网络的外推能力。具体来说，在推理阶段，我们将概率预测的后验预测作为条件，以满足微观尺度上的部分平衡。为了确保贝叶斯调节操作的可操作性，我们使用了集 合卡尔曼算法（Ensemble Kalman algorithm）。我们的研究表明，这种创新方法可以减轻未校正 GNN 输出中出现的不良偏差的影响，并从总体上提高预测的准确性。

Experimental and FEM investigation of bending behaviors of S-core sandwich panel composites

Öztemiz Hasan Murat, Temiz Şemsettin

doi:10.1016/j.ijsolstr.2023.112546

S 型芯夹芯板复合材料弯曲行为的实验和有限元研究

Sandwich panel composites have numerous applications in material technology. The sandwich panel composite structure’s mechanical behavior and performance are determined by the material properties and geometry of the relevant components. The top and bottom sheets of the designed sandwich panel composite material are made of stainless steel-316, the core material is aluminum 1050A-0, and the binding element is DP-8405 acrylic adhesive. Three-point bending tests and finite element models were utilized to investigate the bending behavior of S-core composite sandwich panels. Finite element models have been developed to characterize the effect of composite element bending behavior on variations. The specific flexural modulus and strength of composite S-core sandwich structures can be compared to core structures in the literature in general. As a consequence, the minimum weight design was used as a guideline to produce weight and density-efficient hybrid composite sandwich panels. The load-carrying capacity of the composite panel increased as the wall thickness of the S-shaped core increased when the damage loads were examined in the variations. It has been ascertained that as the core height increases, the load-carrying capacity of the composite panel decreases.

夹芯板复合材料在材料技术领域应用广泛。夹芯板复合材料结构的机械行为和性能由相关部件的材料特性和几何形状决定。所设计的夹芯板复合材料的顶板和底板由不锈钢-316 制成，芯材为铝 1050A-0，粘合元件为 DP-8405 丙烯酸粘合剂。利用三点弯曲试验和有限元模型研究了 S 型芯复合夹芯板的弯曲行为。开发的有限元模型用于描述复合材料弯曲行为对变化的影响。复合 S 型芯材夹层结构的特定弯曲模量和强度可与一般文献中的芯材结构进行比较。因此，最小重量设计被用作生产重量和密度效率高的混合复合夹层板的指导原则。在对破坏载荷的变化进行研究时，复合材料板的承载能力随着 S 形夹芯壁厚的增加而增加。可以确定的是，随着夹芯高度的增加，复合板的承载能力会降低。

Facilitating polymer property prediction with machine learning and Group Interaction Modelling methods

Kazemi-Khasragh Elaheh, Fernández Blázquez Juan P., Garoz David, González Carlos, Haranczyk Maciej

doi:10.1016/j.ijsolstr.2023.112547

利用机器学习和群体相互作用建模方法促进聚合物性能预测

Identification of a suitable polymer material for a given applications requires information about the properties and behavior of the material, which is time-consuming and costly to measure experimentally. In this study, we explore two computational alternatives; namely, Group Interaction Modelling (GIM) and Machine Learning (ML) approaches, as two avenues for predicting six different thermal and mechanical properties of polymers. Random Forest (RF) was employed as ML algorithm. Molecular descriptors for ML and physical input parameters for GIM method were obtained directly from the chemical structure information of polymers. The ML models developed in this study exhibited strong predictive performance, achieving R2 values ranging from 0.83 to 0.955 across the evaluated properties. The accuracy of the ML and GIM method has been compared with each other, and the evaluation is demonstrated that ML approach offers more reliable predictions over the GIM method. Furthermore, we found that the accuracy of the GIM predictions was highly dependent on the accuracy of the Debye temperature values used as an input parameter, particularly for predicting the glass transition temperature. Therefore, for better prediction in GIM procedure, it is essential to use accurate techniques to find the Debye temperature values.

为特定应用确定合适的聚合物材料需要了解材料的特性和行为，而实验测量耗时且成本高昂。在本研究中，我们探索了两种计算方法，即群体交互建模（GIM）和机器学习（ML）方法，作为预测聚合物六种不同热性能和机械性能的两种途径。随机森林（RF）被用作 ML 算法。ML 方法的分子描述符和 GIM 方法的物理输入参数直接从聚合物的化学结构信息中获取。本研究中开发的 ML 模型表现出很强的预测性能，在所评估的各种特性中，R2 值从 0.83 到 0.955 不等。我们比较了 ML 方法和 GIM 方法的准确性，结果表明 ML 方法比 GIM 方法提供了更可靠的预测。此外，我们还发现 GIM 预测的准确性在很大程度上取决于作为输入参数的德拜温度值的准确性，尤其是在预测玻璃化转变温度时。因此，要在 GIM 程序中进行更好的预测，必须使用精确的技术来找到德拜温度值。

Journal of the Mechanics and Physics of Solids

Non-Hermitian wave dynamics of odd plates: Microstructure design and theoretical modelling

Wang Yanzheng, Wu Qian, Tian Yiran, Huang Guoliang

doi:10.1016/j.jmps.2023.105462

奇数板的非赫米梯波动力学：微结构设计和理论建模

The concept of odd elasticity was recently introduced to characterize the elastic behavior of solids that consist of active components, exhibiting an asymmetric elastic modulus tensor. In this paper, we propose, for the first time, the microstructure design of an odd plate, which is composed of a lattice plate with a piezoelectric-patch-based sensor-actuator feed-forward system. By leveraging the nonreciprocal coupling between shear forces and bending curvatures, the odd plate constitutive relation is formulated in the low frequency region, which features as four asymmetric coupling parameters known as “odd parameters”. We reveal that the two-dimensional (2D) odd plates can perform directional wave energy amplification and the amplification angle can be determined analytically through the rotation of coordinate system. We also numerically demonstrate the directional wave amplification phenomena that arise from the optimal combination of odd parameters. In addition, we analytically uncover the presence of Stoneley-like interfacial waves between two plates with two odd parameters in opposite signs, which is further characterized by the numerical simulation. Unlike interfacial waves between topological structures, the interfacial waves between odd plates can exist for any working frequency, enabling the design of some novel waveguides. This research on the control of flexural waves in odd plates could shed lights on 2D non-Hermitian systems in elasticity.

最近提出了奇异弹性的概念，用于描述由活性成分组成的固体的弹性行为，这些活性成分表现出不对称的弹性模量张量。在本文中，我们首次提出了奇数板的微结构设计，它由带有基于压电贴片的传感器-执行器前馈系统的晶格板组成。通过利用剪切力和弯曲曲率之间的非互惠耦合，我们提出了奇数板在低频区域的构成关系，其特征是四个不对称耦合参数，即 "奇数参数"。我们揭示了二维（2D）奇数板可以进行定向波能放大，而且放大角可以通过旋转坐标系来分析确定。我们还从数值上证明了奇数参数的最佳组合所产生的定向波放大现象。此外，我们通过分析发现了两个奇数参数符号相反的两块板之间存在类似斯通莱的界面波，并通过数值模拟进一步证实了这一现象的特征。与拓扑结构之间的界面波不同，奇数板之间的界面波在任何工作频率下都能存在，这使得一些新型波导的设计成为可能。这项关于奇数板挠曲波控制的研究可为弹性领域的二维非ermitian 系统提供启示。

Topology optimization of flexoelectric metamaterials with apparent piezoelectricity

Greco F., Codony D., Mohammadi H., Fernández-Méndez S., Arias I.

doi:10.1016/j.jmps.2023.105477

具有表观压电性的柔电超材料拓扑优化

The flexoelectric effect, coupling polarization and strain gradient as well as strain and electric field gradients, is universal to dielectrics, but, as compared to piezoelectricity, it is more difficult to harness as it requires field gradients and it is a small-scale effect. This drawback can be overcome by suitably designing multiscale metamaterials made of a non-piezoelectric base material but exhibiting apparent piezoelectricity. We develop a theoretical and computational framework to perform topology optimization of the representative volume element of such metamaterials by accurately modeling the governing equations of flexoelectricity using a Cartesian B-spline method, describing geometry with a level set, and resorting to genetic algorithms for optimization. We consider a multi-objective optimization problem where area fraction competes with each one of the four fundamental piezoelectric functionalities (stress/strain sensor/actuator). We computationally obtain Pareto fronts, and discuss the different geometries depending on the apparent piezoelectric coefficient being optimized. Our results show that optimal material architectures strongly depend on the specific functional property being optimized, and that, except for stress actuators, optimal structures are low-area-fraction lattices. In general, we find competitive estimations of apparent piezoelectricity as compared to reference materials such as quartz and PZT ceramics. This opens the possibility to design devices for sensing, actuation and energy harvesting from a much wider, cheaper and effective class of materials.

柔电效应是极化和应变梯度以及应变和电场梯度的耦合，对电介质具有普遍意义，但与压电相比，它更难利用，因为它需要场梯度，而且是一种小尺度效应。通过适当设计由非压电基底材料制成但表现出明显压电性的多尺度超材料，可以克服这一缺点。我们开发了一个理论和计算框架，通过使用笛卡尔 B-样条法精确建模柔电控制方程，用水平集描述几何形状，并借助遗传算法进行优化，从而对此类超材料的代表性体积元素进行拓扑优化。我们考虑了一个多目标优化问题，其中面积分数与四种基本压电功能（应力/应变传感器/致动器）中的每一种都存在竞争关系。我们通过计算获得了帕累托前沿，并根据所优化的表观压电系数讨论了不同的几何结构。我们的研究结果表明，最佳材料结构在很大程度上取决于所优化的特定功能特性，而且除应力致动器外，最佳结构都是低面积分数晶格。总体而言，与石英和 PZT 陶瓷等参考材料相比，我们发现表观压电性的估计值很有竞争力。这为利用更广泛、更便宜、更有效的材料设计传感、致动和能量收集设备提供了可能。

Mechanics and topology of twisted hyperelastic filaments under prescribed elongations: Experiment, theory, and simulation

Liu Lei, Liu Hao, He Yuming, Liu Dabiao

doi:10.1016/j.jmps.2023.105478

规定伸长率下扭曲超弹性细丝的力学和拓扑学：实验、理论和模拟

Soft filaments can be stretched, bent, and twisted, exhibiting complex configurations. When a filament undergoes large torsional deformation, it can display instabilities, and its post-buckling behavior and configuration evolution differs significantly from that observed under small deformation. We study the mechanics and topologically complex morphologies of twisted rubber filaments under prescribed elongation by combining experiment and finite strain theory. Based on the Mooney-Rivlin model, a finite strain theory of the hyperelastic filament under combined tension, bending, and torsion has been established, accounting for both geometrical and material nonlinearities. An experimental and theoretical morphological phase diagram is constructed as a function of the twist density and the initial elongation. The buckling and post-buckling behaviors of the twisted rubber filaments under prescribed elongation are well captured by the theory that considers geometrical nonlinearity and self-contact. By tracking the interconversion of link, twist, and writhe, we accurately determine the configuration and the critical points of phase transitions. The theoretical predictions agree closely with the measurements. This work sheds light on understanding the morphological complexity of the loaded hyperelastic rod.

软丝可以拉伸、弯曲和扭曲，呈现出复杂的构型。当丝状物发生大的扭转变形时，会表现出不稳定性，其扭转后的行为和构型演变与小变形时的行为和构型演变有很大不同。我们结合实验和有限应变理论，研究了扭转橡胶丝在规定伸长率下的力学和拓扑复杂形态。在穆尼-里夫林模型的基础上，建立了超弹性长丝在拉伸、弯曲和扭转联合作用下的有限应变理论，同时考虑了几何和材料非线性因素。实验和理论形态相图是扭曲密度和初始伸长率的函数。考虑了几何非线性和自接触的理论很好地捕捉到了扭曲橡胶丝在规定伸长率下的屈曲和屈曲后行为。通过跟踪链接、扭曲和扭转的相互转换，我们准确地确定了相变的配置和临界点。理论预测与测量结果非常吻合。这项工作有助于理解加载超弹性杆的形态复杂性。

Asymptotically matched extrapolation of fishnet failure probability to continuum scale

Xu Houlin, Vievering Joshua, Nguyen Hoang T., Zhang Yupeng, Le Jia-Liang, Bažant Zdeněk P.

doi:10.1016/j.jmps.2023.105479

鱼网失效概率渐近匹配外推至连续尺度

Motivated by the extraordinary strength of nacre, which exceeds the strength of its fragile constituents by an order of magnitude, the fishnet statistics became in 2017 the only analytically solvable probabilistic model of structural strength other than the weakest-link and fiber-bundle models. These two models lead, respectively, to the Weibull and Gaussian (or normal) distributions at the large-size limit, which are hardly distinguishable in the central range of failure probability. But they differ enormously at the failure probability level of 10^-6, considered as the maximum tolerable for engineering structures. Under the assumption that no more than three fishnet links fail prior to the peak load, the preceding studies led to exact solutions intermediate between Weibull and Gaussian distributions. Here massive Monte Carlo simulations are used to show that these exact solutions do not apply for fishnets with more than about 500 links. The simulations show that, as the number of links becomes larger, the likelihood of having more than three failed links up to the peak load is no longer negligible and becomes large for fishnets with thousands of links. A differential equation is derived for the probability distribution of not-too-large fishnets, characterized by the size effect, the mean and the coefficient of variation. Although the large-size asymptotic distribution is beyond the reach of the Monte Carlo simulations, it can by illuminated by approximating the large-scale fishnet as a continuum with a crack or a circular hole. For the former, instability is proven via complex variables, and for the latter via a known elasticity solution for a hole in a continuum under shear. The fact that rows or enclaves of link failures acting as cracks or holes can form in the large-scale continuum at many random locations necessarily leads to the Weibull distribution of the large fishnet, given that these cracks or holes become unstable as soon they reach a certain critical size. The Weibull modulus of this continuum is estimated to be about the triple of that for the central range of small fishnets. The new model is expected to allow spin-offs for printed materials with octet architecture maximizing the strength–weight ratio.

珍珠岩的强度非同一般，比其脆弱成分的强度高出一个数量级，受此激励，鱼网统计在2017年成为除弱链和纤维束模型之外唯一可分析求解的结构强度概率模型。这两种模型分别导致大尺寸极限的威布尔分布和高斯分布（或正态分布），它们在破坏概率的中心范围内几乎没有区别。但在故障概率为10^-6，被认为是工程结构可承受的最大值。假设在峰值载荷之前失效的鱼网链接数不超过三个，则前面的研究得出了介于威布尔分布和高斯分布之间的精确解。这里使用大规模蒙特卡罗模拟来说明，这些精确解并不适用于超过约 500 个链接的鱼网。模拟结果表明，随着链路数量的增加，在峰值负载时出现三个以上故障链路的可能性不再可以忽略，对于拥有数千个链路的鱼网来说，这种可能性变得很大。对于不太大的鱼网的概率分布，可以得出一个微分方程，该方程以规模效应、平均值和变异系数为特征。虽然大尺寸渐近分布超出了蒙特卡洛模拟的范围，但可以通过将大尺度鱼网近似为带有裂缝或圆孔的连续体来加以阐明。对于前者，不稳定性可以通过复杂变量来证明，而对于后者，则可以通过已知的连续体中的孔在剪切力作用下的弹性解来证明。在大尺度连续体中，许多随机位置都可能形成成行或成围的裂缝或孔洞，这必然导致大鱼网的韦布尔分布，因为这些裂缝或孔洞一旦达到某个临界尺寸就会变得不稳定。据估计，这种连续体的威布尔模量约为小鱼网中心范围的三倍。新模型有望衍生出八面体结构的印刷材料，最大限度地提高强度-重量比。

Mechanics of Materials

A shear-lag model for laminated beams with extreme modulus mismatch between layers

Wang Zheliang, Sheng Hao, Lin Xinyi, Rao Yifan, Liu Jia, Lu Nanshu

doi:10.1016/j.mechmat.2023.104844

层间模量极度不匹配的层压梁剪力滞后模型

Multilayer laminated beams, comprised of alternating stiff and soft layers, are widely used in flexible electronics and photonics. These structures exhibit complex mechanical behaviors that deviate from the Euler–Bernoulli beam theory under conditions of extreme inter-layer modulus mismatch. Extending beyond prior studies on trilayer beams, we present an analytical framework for laminated beams with arbitrary number of layers subjected to various bending conditions, and validate our theory with finite element analysis. We define an equivalent flexural rigidity, exploring its dependence on position and deformation, and systematically examine the impact of the number of layers, applied deformation, layer properties, and the layer aspect ratio.

由软硬交替层组成的多层叠层梁广泛应用于柔性电子学和光子学领域。在层间模量极度不匹配的条件下，这些结构会表现出偏离欧拉-伯努利梁理论的复杂力学行为。在先前对三层梁研究的基础上，我们提出了一个分析框架，适用于在各种弯曲条件下具有任意层数的层压梁，并通过有限元分析验证了我们的理论。我们定义了等效抗弯刚度，探讨了其与位置和变形的关系，并系统地研究了层数、应用变形、层属性和层长宽比的影响。

International Journal of Plasticity

Investigations on austenite stability and martensitic transformation kinetics of a medium Mn steel under different strain states

Zou Yuming, Gao Qihan, Ding Hua, Zhang Yu, Tang Zhengyou

doi:10.1016/j.ijplas.2023.103788

不同应变状态下中锰钢的奥氏体稳定性和马氏体转变动力学研究

Martensitic transformation has received wide attention due to its significant role in improving mechanical properties of medium Mn steels. In this paper, three typical strain states in sheet metal forming, uniaxial tension, biaxial tension and plane strain states, were selected to investigate the effect of the strain state on martensitic transformation of a medium Mn steel at room temperature. The experimental results show that the austenite stability of the medium Mn steel is seriously strain state dependent. The sample deformed under the plane strain state exhibits the lowest austenite stability, while it progressively increases for biaxial tension and uniaxial tension states. The microstructural evolution and the strain partitioning behavior of the material are characterized. It is indicated that the strains in austenite under different deformation modes are quite different even though the overall deformation conditions are similar, which leads to different transformation rates of γ → α’ transformation. Besides, the ε-martensitic transformation that only generates under the plane strain state further decreases the austenite stability. A strain state dependent α’-martensitic transformation kinetics law is proposed that incorporates the effect of the stress triaxiality and Lode angle parameter, which provides a reasonable prediction of γ → α’ transformation in the medium Mn steel over a wide range of strain states.

马氏体转变在改善中锰钢机械性能方面发挥着重要作用，因此受到广泛关注。本文选取金属板材成形过程中的三种典型应变状态，即单轴拉伸、双轴拉伸和平面应变状态，研究应变状态对室温下中锰钢马氏体转变的影响。实验结果表明，中锰钢的奥氏体稳定性严重依赖于应变状态。在平面应变状态下变形的样品奥氏体稳定性最低，而在双轴拉伸和单轴拉伸状态下，奥氏体稳定性逐渐增加。对材料的微观结构演变和应变分配行为进行了表征。结果表明，尽管整体变形条件相似，但不同变形模式下奥氏体的应变却大不相同，这导致了γ → α'转变的转化率不同。此外，只有在平面应变状态下才产生的ε-马氏体转变会进一步降低奥氏体的稳定性。结合应力三轴性和洛德角参数的影响，提出了与应变状态相关的α'-马氏体转变动力学规律，从而合理预测了中锰钢在广泛应变状态下的γ → α'转变。

Thin-Walled Structures

Experimental Investigation on Seismic Performance of Cold-Formed Steel Strap-Braced Stud Walls Under Lateral Cyclic and Vertical Loading

Rad Pouya Lotfi, Clifton Charles, Lim James, Hajirasouliha Iman

doi:10.1016/j.tws.2023.111312

冷弯钢带支撑龙骨墙在侧向循环和垂直荷载作用下的抗震性能实验研究

Cold-formed steel (CFS) construction offers several benefits over traditional construction, including being lightweight, sustainable, recyclable, quick to build, insect and rot-resistant, and suitable for computer-aided design and manufacture. Despite extensive research on CFS elements, there are still gaps in our understanding of the behaviour of CFS structural systems, particularly their response to severe earthquake events. This experimental program aims to provide a better understanding on the seismic behaviour of strap-braced stud-walls as a lateral force resisting system for residential medium-rise buildings. An innovative test rig is developed that is capable of applying a constant vertical load during lateral cyclic testing, replicating the loading conditions expected during an earthquake event in such cases. For the first time, seven full-scale tests are conducted on CFS walls under vertical and horizontal loading using standard sections in New Zealand. The vertical capacity, lateral stiffness, ultimate strength, ductility, and failure mechanisms of the specimens are investigated. Subsequently, a modified detailing is suggested, which allows CFS walls to exhibit considerably better seismic behaviour compared to the systems with conventional detailing. It is shown that by adopting the modified detailing, CFS walls exhibit an ideal elastic-plastic curve with negligible degradation in successive cycles and a high ductility factor exceeding 5. The results of this study should prove useful for more efficient design of CFS strap-braced stud walls for mid-rise buildings.

与传统建筑相比，冷弯型钢（CFS）建筑具有多种优点，包括重量轻、可持续发展、可回收、建造速度快、防虫和防腐，以及适合计算机辅助设计和制造。尽管对 CFS 构件进行了广泛的研究，但我们对 CFS 结构系统的行为，尤其是对其在严重地震事件中的反应的了解仍然存在差距。本实验项目旨在更好地了解作为中层住宅楼抗侧力系统的带肋螺栓墙的抗震性能。我们开发了一种创新的试验台架，能够在横向循环试验中施加恒定的垂直荷载，复 制地震事件中的预期加载条件。在新西兰，首次使用标准截面对 CFS 墙体在垂直和水平荷载下进行了七次全尺寸测试。对试件的垂直承载力、横向刚度、极限强度、延展性和破坏机制进行了研究。随后，提出了一种修改后的细部设计，与采用传统细部设计的系统相比，它能使 CFS 墙体表现出更好的抗震性能。研究表明，采用修改后的细部构造后，CFS 墙体表现出理想的弹塑性曲线，在连续循环中的衰减可以忽略不计，延性系数超过 5。这项研究的结果将有助于更有效地设计用于中层建筑的 CFS 带支撑龙骨墙。

Forming characteristics of thin-walled tubes manufactured by free bending process-based nontangential rotation bending die

Hu Shenghan, Cheng Cheng, El-Aty Ali Abd, Zheng Shuo, Wu Cong, Luo Haoran, Guo Xunzhong, Tao Jie

doi:10.1016/j.tws.2023.111313

基于自由弯曲工艺的非切线旋转弯曲模具制造的薄壁管的成型特性

The free-bending process of a metal tube involves a geometric relationship between the eccentricity, the rotation angle of the bending die, the deformation zone length, and the bending radius. Ideally, during the forming process, the contact position between the bending die, and the outer bend of the tube remains tangent. However, due to factors such as the clearance of the bending die and material properties, the rotation angle can be adjusted within a specific range while still ensuring smooth tube formation. The tangential state is disrupted when the rotation angle changes, resulting in overbending or underbending. Thus, in this study, a new theoretical analysis of the free bending process, accounting for clearance, was developed to analyse the material flow and changes in the bending radius during the nontangential contact between the bending die and the tube. In addition, the reasons for achieving smooth tube bending even after adjusting the rotation angle were explained, and the deformation mechanism of the tube under the combined effects of additional tangential force from the bending die and axial propulsive force was analysed. Furthermore, the impact of the rotation angle on the bending radius and the displacement of the strain neutral layer (strain NL) was determined. Afterwards, finite element (FE) modeling and forming experiments were conducted to verify the proposed theoretical analysis under different deformation zone lengths and eccentricities conditions. Besides, the distribution of the inner and outer wall thicknesses of the tube under the nontangential rotation of the bending die was further analysed. The simulation and experimental results fit well with that obtained from theoretical analysis.

金属管的自由弯曲过程涉及偏心率、弯曲模具的旋转角度、变形区长度和弯曲半径之间的几何关系。理想情况下，在成型过程中，弯曲模具与管材外部弯曲部分之间的接触位置保持相切。然而，由于弯曲模具的间隙和材料特性等因素，旋转角度可在特定范围内调整，同时仍能确保管材顺利成型。当旋转角度发生变化时，切向状态就会被破坏，从而导致弯曲过度或弯曲不足。因此，本研究对自由弯曲过程进行了新的理论分析，考虑了间隙因素，分析了弯曲模具与管材非切线接触过程中的材料流动和弯曲半径变化。此外，还解释了即使调整旋转角度也能实现管材平滑弯曲的原因，并分析了在弯曲模的附加切向力和轴向推进力的共同作用下管材的变形机制。此外，还确定了旋转角度对弯曲半径和应变中性层（应变 NL）位移的影响。随后，在不同的变形区长度和偏心率条件下，进行了有限元（FE）建模和成形实验，以验证所提出的理论分析。此外，还进一步分析了弯曲模具非直角旋转时管材内外壁厚度的分布情况。模拟和实验结果与理论分析结果吻合良好。

Experimental and numerical investigation on cold-formed steel zed section beams with complex edge stiffeners

Li Qiu-Yun, Young Ben

doi:10.1016/j.tws.2023.111315

带复杂边缘加劲件的冷弯型钢 zed 截面梁的实验和数值研究

This paper describes the experimental and numerical investigation on the flexural performance of cold-formed steel (CFS) zed section members bent about the neutral axis parallel to the flanges. In the test program, twelve pairs of zed section specimens fabricated from steel sheets of grades G450, G500 and G550 were loaded under four-point bending. Three series of sectional shapes, namely the zed sections with plain flanges as well as complex edge stiffeners consisting of double-fold inward and outward return lips, were devised for the test specimens. In the numerical investigation, the finite element model of four-point bending members, which was developed using ABAQUS and calibrated against the experimental results, was adopted to predict the behaviour of CFS unstiffened and edge-stiffened zed section beams over wide ranges of flange-to-web width ratio, lip-to-flange width ratio, return lip-to-lip width ratio and cross-sectional compactness. Furthermore, underpinned by the bending capacities acquired from the 12 experiments and 222 FE analyses in this study as well as 22 tests available in the literature, it was demonstrated that the current direct strength method (DSM) codified in the AISI S100 generally provided conservative flexural strength predictions for the unstiffened zed section members, while led to overall slightly unconservative design for the edge-stiffened zed section beams. In addition, based upon the DSM-based approaches that were addressed in the previous studies to account for the effect of local-distortional interaction, the nominal flexural strengths of the CFS zed section members with simple and complex edge stiffeners were found to be underestimated by 17% to 21% on average. Accordingly, the modified DSM formulae were recommended in this study for the CFS unstiffened and edge-stiffened zed section beams bent about the neutral axis parallel to the flanges.

本文介绍了对冷弯型钢（CFS）zed 截面构件绕平行于翼缘板的中轴线弯曲的抗弯性能进行的实验和数值研究。在测试程序中，12 对由 G450、G500 和 G550 级钢板制成的zed 截面试样在四点弯曲下加载。试验试样设计了三个系列的截面形状，即带普通翼缘的zed截面，以及由双倍向内和向外回唇组成的复杂边缘加劲件。在数值研究中，使用 ABAQUS 开发了四点弯曲构件的有限元模型，并根据实验结果进行了校准，该模型用于预测 CFS 非加劲和边缘加劲 "zed "截面梁在翼缘板与腹板宽度比、唇缘与翼缘板宽度比、回唇与唇缘宽度比和横截面密实度的宽范围内的行为。此外，根据本研究中的 12 次实验和 222 次有限元分析以及文献中的 22 次测试所获得的抗弯强度，可以证明 AISI S100 中编纂的现行直接强度法（DSM）对未加刚度的轧制截面构件的抗弯强度预测一般比较保守，而对边缘加刚度的轧制截面梁的设计则总体上略显保守。此外，根据之前研究中考虑局部扭曲相互作用影响的基于 DSM 的方法，发现带有简单和复杂边缘加劲件的 CFS zed 截面构件的名义抗弯强度平均被低估了 17% 至 21%。因此，本研究建议对绕平行于翼缘的中轴弯曲的 CFS 非加劲梁和边缘加劲 Zed 截面梁采用修改后的 DSM 公式。

Effects of the strain gradients on the band structures of the elastic waves propagating in 1D phononic crystals: An analytical approach

Hosseini Seyed Mahmoud, Sladek Jan, Sladek Vladimir, Zhang Chuanzeng

doi:10.1016/j.tws.2023.111316

应变梯度对在一维声子晶体中传播的弹性波的带状结构的影响：分析方法

In this paper, an analytical method is proposed for the analysis of the effects of the strain gradients on the frequency band structures and band-gaps of the elastic waves propagating in one-dimensional (1D) nano-sized phononic crystals (PCs). The considered 1D nano-sized PCs are made of periodic unit-cells containing a metal section and an epoxy section. The strain gradients are taken into account to obtain the governing equations by using the strain energy, the kinetic energy and the Hamilton's principle. An analytical solution based on the transfer matrix method is derived to compute the frequency dispersion curves or band structures of the elastic waves. The continuity conditions on the interface between the neighboring sections and the periodic boundary conditions for the unit-cell are satisfied using the proposed analytical method. Two band-gap characteristics, namely the starting frequency and the width of each band-gap, are defined and investigated. The effects of the small-scale parameters in the strain-gradient theory on the band structures and the band-gap characteristics are analyzed and discussed in detail. It is demonstrated that the strain gradients may significantly influence the frequency band structures and the band-gap characteristics of the elastic waves propagating in 1D nano-sized PCs.

本文提出了一种分析方法，用于分析应变梯度对在一维（1D）纳米声子晶体（PC）中传播的弹性波的频带结构和带隙的影响。所考虑的一维纳米级声波晶体由包含金属部分和环氧树脂部分的周期性单元单元组成。考虑到应变梯度，利用应变能、动能和汉密尔顿原理获得了控制方程。基于传递矩阵法得出的解析解可以计算出弹性波的频散曲线或频带结构。利用所提出的分析方法，可以满足相邻部分之间界面的连续性条件和单元单元的周期性边界条件。定义并研究了两个带隙特征，即起始频率和每个带隙的宽度。详细分析和讨论了应变梯度理论中的小尺度参数对带状结构和带隙特性的影响。结果表明，应变梯度会显著影响在一维纳米 PC 中传播的弹性波的频带结构和带隙特性。

Fatigue resistance of rib-to-bimetallic steel deck welded joints in orthotropic steel bridge decks

Liao Xiaowei, Wei Hanlin, Pan Hongyang, Li Hai-Ting, Sun Bo, Xin Haohui

doi:10.1016/j.tws.2023.111318

正交异性钢桥面中肋条与双金属钢桥面焊接接头的抗疲劳性能

The stainless-cladding techniques have been applied in the top plate of the orthotropic steel decks in the high-speed railway steel bridges to improve the corrosion and wear resistance. The rib-to-deck (RD) welded joint with the stainless-clad bimetallic steel deck plate becomes a new critical fatigue detail. This study firstly examines the fatigue performance of this full-scale new RD joint through six high-cycle constant-amplitude fatigue tests and two beach-mark tests under eccentric over-rib loading. The structural hot-spot stress at the weld toe on the deck plate is obtained by strain gauges and the linear extrapolation method for each RD specimen before the cyclic loading. Experimental results indicate that five RD specimens suffer from the toe-deck failure modes, while the rests encounter root-deck cracking. The fatigue strength of these new RD joints satisfies the FAT100 hot-spot stress S-N curve based on the IIW design recommendation. Numerical simulation is further conducted to investigate the effect of different cracking modes and welding technologies on the fatigue crack propagation behavior of this new RD joint. Root-deck cracking mode shows weakly higher fatigue resistance than the toe-deck failure case. Using the double-side welds between the U-rib and deck plate, and the thickened-edge U-rib technology can slightly enhance the fatigue life in terms of toe-deck cracking mode in contrast with the traditional single-side groove welds. Experimental and numerical validation quantify the excellent fatigue performance of this new RD joint in comparison with the other types of RD welded joints.

高速铁路钢桥的正交异性钢桥面顶板采用了不锈钢包覆技术，以提高其耐腐蚀性和耐磨性。与不锈钢包覆双金属钢桥面板的肋对桥面（RD）焊接接头成为一个新的关键疲劳细节。本研究首先通过六次高循环恒定振幅疲劳试验和两次偏心过肋加载下的海滩标记试验，对这种全尺寸新型 RD 接头的疲劳性能进行了研究。在循环加载前，通过应变片和线性外推法获得了每个 RD 试件在甲板板焊趾处的结构热点应力。实验结果表明，五个 RD 试样出现了焊趾-甲板失效模式，其余试样则出现了根部-甲板开裂。这些新型 RD 接头的疲劳强度满足基于 IIW 设计建议的 FAT100 热点应力 S-N 曲线。为了研究不同开裂模式和焊接技术对这种新型 RD 接头疲劳裂纹扩展行为的影响，进一步进行了数值模拟。根部开裂模式的抗疲劳性能略高于趾部开裂模式。与传统的单面沟槽焊缝相比，在 U 形肋和甲板板之间采用双面焊缝和加厚边缘 U 形肋技术可略微提高趾部开裂模式的疲劳寿命。实验和数值验证表明，与其他类型的 RD 焊接接头相比，这种新型 RD 接头具有优异的疲劳性能。

Effect of temperature on the plastic flow and strain hardening of direct-quenched ultra-high strength steel S960MC

Ghafouri Mehran, Afkhami Shahriar, Pokka Aki-Petteri, Javaheri Vahid, Togiani Amir, Larkiola Jari, Björk Timo

doi:10.1016/j.tws.2023.111319

温度对直接淬火超高强度钢 S960MC 的塑性流动和应变硬化的影响

This study investigates the plastic deformation and hardening behavior of the direct-quenched ultra-high strength steel S960MC at various temperatures ranging from room temperature to 900 ℃. In this regard, the Hollomon and Voce equations are used to model the hardening behavior of the material at different temperatures. The suitability of each equation to predict the plastic flow of S960MC is evaluated based on the best resulted fit for the material. In addition, microstructural investigations are carried out to indicate the correlations between the microstructural changes, occurring in the range of room temperature to 900 ℃, and hardening behavior and governing parameters. The Hollomon approach showed deviations from the experimental results for room to intermediate temperatures; however, the Voce equation modeled the material's strain hardening and flow behavior more successfully for the entire temperature range of room temperature–900 ℃. Additionally, there was a significant consistency between the Kocks-Mecking and Voce parameters. Dislocation interactions, dynamic strain aging, dynamic recrystallization, dynamic recovery, tempering (martensite decomposition), and austenite formation were the most influential microstructural features on the hardening behavior at various temperatures. The correlations between these microstructural features and hardening parameters were established satisfactorily for both the Hollomon and Voce approaches.

本研究探讨了直接淬火超高强度钢 S960MC 在从室温到 900 ℃ 的不同温度下的塑性变形和硬化行为。其中，霍洛蒙方程和沃斯方程用于模拟材料在不同温度下的硬化行为。根据材料的最佳拟合结果，评估了每个方程预测 S960MC 塑性流动的适用性。此外，还进行了微观结构研究，以说明在室温至 900 ℃ 范围内发生的微观结构变化与硬化行为和控制参数之间的相关性。霍洛蒙方法在室温至中间温度范围内显示出与实验结果的偏差；然而，在室温至 900 ℃ 的整个温度范围内，Voce 方程更成功地模拟了材料的应变硬化和流动行为。此外，Kocks-Mecking 和 Voce 参数之间有显著的一致性。位错相互作用、动态应变时效、动态再结晶、动态恢复、回火（马氏体分解）和奥氏体形成是对不同温度下的硬化行为影响最大的微观结构特征。这些微观结构特征与硬化参数之间的相关性在霍洛蒙方法和 Voce 方法中都得到了令人满意的确定。

Characterization of Multiple Debris Cloud Impacts-induced Pitting Damage Evolution in Spacecraft Structures Using Temperature-dependent Ultrasonic Nonlinearity

Chi Runqiang, Gao Jiaxin, Hu Diqi, Zhang Weigui, Pang Baojun, Cao Wuxiong

doi:10.1016/j.tws.2023.111322

利用随温度变化的超声波非线性表征多次碎片云撞击诱发的航天器结构点状损伤演变

Facing the harsh cryogenic-elevated temperature condition, evaluation of the debris cloud-induced pervasive but highly complex pitting damage in manned spacecraft structures, featuring multitudinous small-scale craters and cracks disorderedly scattered over a wide region, accompanied by a diversity of micro-damages, is hitherto still a challenging task. In line with the fact that the use of ultrasonic nonlinearity is restricted by its intrinsic vulnerability to measurement contamination, in particular temperature fluctuations. With this motivation, an insight into the modulation mechanism of typical elastic parameters of material at macroscopic under varying temperatures, as well as microscopic interatomic potential, is achieved via theoretical analysis. Based on this, temperature sensitivity coefficients (TSCs) of these elastic parameters are obtained, and a nonlinear temperature sensitivity index (TSI) is established. On this basis, an active TSI-based evaluation method is proposed to improve the accuracy and reliability of pitting damage evaluation by controlling detection temperature (i.e., exploitation of the benign aspects of the temperature sensitivity of ultrasonic nonlinearity), rather than eliminating or compensating for its adverse effect, when other nonlinear sources interference. This method is experimentally corroborated, in which the multiple debris cloud impacts-induced accumulated pitting damage are accurately and intuitively characterized through temperature control, in terms of its severity and distribution characteristics, which is consistent with the theoretical prediction. These findings provide an active structural health monitoring (SHM) strategy for promoting the practical application of this proposed approach for characterizing pitting damage evolution in manned spacecraft in qualitative and semi-quantitative manners.

在严酷的低温条件下，评估载人航天器结构中由碎片云引起的普遍但高度复杂的点状损伤（其特征是在广泛区域内无序分布着许多小尺度的凹坑和裂纹，并伴有多种微损伤），迄今为止仍是一项具有挑战性的任务。由于超声波非线性本身易受测量污染，特别是温度波动的影响，因此其使用受到限制。基于这一动机，我们通过理论分析深入了解了材料在不同温度下的宏观典型弹性参数以及微观原子间势能的调制机制。在此基础上，获得了这些弹性参数的温度敏感系数（TSCs），并建立了非线性温度敏感指数（TSI）。在此基础上，提出了一种基于 TSI 的主动评估方法，当其他非线性源干扰时，通过控制检测温度（即利用超声非线性温度敏感性的良性方面），而不是消除或补偿其不利影响，来提高点蚀损伤评估的准确性和可靠性。实验证实了这种方法，通过温度控制，可以准确、直观地描述多个碎片云撞击引起的累积点蚀损伤的严重程度和分布特征，这与理论预测是一致的。这些发现提供了一种积极的结构健康监测（SHM）策略，可促进实际应用这种拟议方法，以定性和半定量的方式确定载人航天器点蚀损伤演变的特征。

Frequency veering and nonlinear coupled vibration analysis of variable stiffness composite plates with curvilinear fiber paths

Liu Xiaofeng, Sun Wei, Liu Honghao, Du Dongxu, Ma Hongwei

doi:10.1016/j.tws.2023.111323

具有曲线纤维路径的变刚度复合板的频率偏移和非线性耦合振动分析

The coupling forced vibration behaviors of a variable stiffness plate with curvilinear fiber paths at mode veering regions caused by variations of fiber angle have been rarely found in previous papers, especially in the presence of considering the complex material nonlinearity of composite materials. In this paper, the variable stiffness plate of carbon fiber reinforced composites (CFRC) with curvilinear fiber paths is taken as the research object, and the influence of curvilinear fiber paths on its natural characteristics and vibration responses are studied in detail on the basis of considering the material nonlinearity of CFRC. Firstly, it is found that the variations of curvilinear fiber paths can cause complex frequency veering behavior of the variable stiffness plate, and lead to the appearance of irregular modal shapes formed by modal interaction. Then, the forced vibration response of the variable stiffness plate in the frequency veering region is analyzed methodically, and the variation rules of the vibration response under modal interaction is obtained. After analyzing the nonlinear vibration response of the variable stiffness plate under the combined influence of modal interaction and CFRC material nonlinearity, the mechanism of complex nonlinear dynamic behavior of variable stiffness plate in frequency veering region is further investigated.

在以往的论文中，尤其是在考虑复合材料复杂的材料非线性的情况下，很少发现具有曲线纤维路径的变刚度板在模态偏转区域因纤维角度变化而产生的耦合受迫振动行为。本文以具有曲线纤维路径的碳纤维增强复合材料（CFRC）变刚度板为研究对象，在考虑 CFRC 材料非线性的基础上，详细研究了曲线纤维路径对其自然特性和振动响应的影响。首先，研究发现曲线纤维路径的变化会引起变刚度板复杂的频率偏移行为，并导致模态相互作用形成的不规则模态形状的出现。然后，有方法地分析了变刚度板在频率偏移区域的受迫振动响应，并得到了模态相互作用下振动响应的变化规律。在分析了变刚度板在模态相互作用和 CFRC 材料非线性共同影响下的非线性振动响应后，进一步研究了变刚度板在频率偏移区域的复杂非线性动力行为的机理。