今日更新：International Journal of Solids and Structures 2 篇，Journal of the Mechanics and Physics of Solids 2 篇，International Journal of Plasticity 1 篇，Thin-Walled Structures 9 篇International Journal of Solids and StructuresConsistent memory surface model for plateau and hardening regionsMasaki Teranishi, Kensaku Kaneko, Hiroshi Hirata, Noritake Hiyoshidoi:10.1016/j.ijsolstr.2024.112787高原和硬化区域的一致记忆面模型Mild steels are frequently used in building structures because of their high strength, productivity, processability, and weldability. One key feature of mild steels is their yield plateau, which is followed by a hardening region in the stress–strain relationship. During large earthquakes, building members can experience a large plastic strain whose amplitude is difficult to predict beforehand. Constitutive equations applicable to the full-range strain field are necessary for accurate structural safety evaluation. This study provides novel constitutive equations for the plateau region, capable of reproducing a yield plateau. A set of hardening constants was proposed to satisfy the consistency condition of the plastic multiplier under any loading pattern. The closed form of the stress–strain relationship was derived to calibrate the material constants. The material constants were calibrated using two types of material test results. The results of the proposed model were consistent with the material test results under cyclic loading at various strain amplitudes. This was validated by comparing the shear buckling and lateral torsional buckling test results of an H-shaped beam with the finite element analysis (FEA) results. The numerical demonstration also highlighted the significance of not only material constitutive laws but also the introduction of residual stress and initial imperfections in reproducing the pre- and post-buckling behaviors. The convergence of the residual force for the proposed model was equivalent to those of the authors’ previous model and the Chaboche model. These results indicate that the proposed model can predict hardening phenomena at the material and structural levels in the plateau and hardening regions.低碳钢因其高强度、高生产率、可加工性和可焊接性而常用于建筑结构。低碳钢的一个主要特点是屈服高原，其后是应力-应变关系中的硬化区。在大地震中，建筑构件可能会出现较大的塑性应变，其振幅很难事先预测。适用于全范围应变场的构造方程对于准确的结构安全评估十分必要。本研究为高原区提供了新的构造方程，能够再现屈服高原。提出了一组硬化常数，以满足任何加载模式下塑性乘数的一致性条件。得出了应力-应变关系的封闭形式，以校准材料常数。利用两种材料的测试结果对材料常数进行了校准。建议模型的结果与各种应变振幅下循环加载的材料测试结果一致。通过比较 H 形梁的剪切屈曲和横向扭转屈曲试验结果与有限元分析（FEA）结果，验证了这一点。数值论证还强调了在再现屈曲前和屈曲后行为时，不仅要考虑材料构成规律，还要考虑残余应力和初始缺陷的引入。所提出模型的残余力收敛性与作者之前的模型和 Chaboche 模型相当。这些结果表明，所提出的模型可以在材料和结构层面预测高原和硬化区域的硬化现象。Shakedown of metallic sandwich beams when subjected to repeated impact loadingsZengshen Yue, Zhouyu Han, Xin Wang, Runpei Yu, Yilin Qu, Pengfei Wang, Zhenyu Zhao, Qiancheng Zhang, Tian Jian Ludoi:10.1016/j.ijsolstr.2024.112793 金属夹层梁在反复冲击荷载作用下的振动试验When a monotonic metallic beam/plate subjected to repeated dynamic loadings with fixed impact level experiences elastoplastic deformation, its measurable deformations may cease to develop for further repetitions of the same dynamic load: this phenomenon was referred to as “pseudo-shakedown” in previous studies (Jones, 2014; Shen and Jones, 1992). Would pseudo-shakedown occur in a metallic sandwich structure under repeated shock loadings remains elusive. A combined experimental and numerical study was carried out to explore whether dynamic shakedown could occur in all-metallic ultralightweight corrugated core sandwich beams. For repeated impact tests, the sandwich beams were fabricated via the sequential process of cutting-stamping-vacuum brazing. When subjected to repeated impact loads (achieved via aluminum foam projectiles launched from a light gas gun), the dynamic responses of each sandwich specimen - including structural evolutions, beam deflections, and deformation/failure modes - were measured. Experimental results revealed that, depending upon the level of impact momentum applied to the sandwich beam, either dynamic shakedown or progressive failure could occur. The method of finite elements (FE) was subsequently employed to simulate the repeated shock tests, which was validated against experimental measurements, with good agreement achieved. To explore the physical mechanisms underlying the observed dynamic shakedown, the FE results of final plastic energy and effective plastic strain distribution in the sandwich beam were extracted and analyzed. When shakedown occurred, the measurable permanent deformation of the sandwich beam kept a relatively stable state, but its plastic energy remained positive, which is different from its monolithic beam/plate counterpart (i.e., plastic energy dropping to zero during dynamic shakedown). Such difference is mainly attributed to stress concentration occurring at the connecting joint points between the corrugated core and face sheets of sandwich and clamped endings, which produces plastic deformations that are difficult to reflect in overall large deformations of the beam. Consequently, the dynamic shakedown of metallic corrugated core sandwich beam captured in this study appears to be inexhaustive and hence may be termed as the “apparent pseudo-shakedown” (with danger lurking in the welding joints as well as clamped endings). Finally, based on a simplified bi-linear hardening constitutive law, the mechanisms underlying the dynamic shakedown of sandwich beam were further discussed from a purely base material point of view.当单调的金属梁/板承受固定冲击水平的重复动态载荷时，会发生弹塑性变形，在进一步重复相同的动态载荷时，其可测量的变形可能会停止发展：在之前的研究中，这种现象被称为 "伪抖动"（Jones，2014 年；Shen 和 Jones，1992 年）。金属夹层结构在反复冲击载荷作用下是否会发生伪抖动仍是一个未知数。为了探索全金属超轻波纹芯夹芯梁是否会发生动态抖动，我们开展了一项实验和数值研究。为了进行反复冲击试验，夹层梁是通过切割-冲压-真空钎焊的连续过程制造的。在受到反复冲击载荷（通过轻型气 枪发射的铝泡沫弹丸实现）时，测量了每个夹层试样的动态响应，包括结构演变、横梁挠度和变形/失效模式。实验结果表明，根据施加在夹层梁上的冲击动量水平，可能会发生动态抖动或渐进失效。随后，采用有限元（FE）方法模拟了反复冲击试验，并与实验测量结果进行了验证，结果一致。为了探索观察到的动态晃动的物理机制，对夹层梁中最终塑性能量和有效塑性应变分布的有限元结果进行了提取和分析。发生晃动时，夹层梁的可测量永久变形保持相对稳定的状态，但其塑性能仍为正值，这与整体梁/板不同（即在动态晃动期间塑性能降至零）。造成这种差异的主要原因是夹层结构的波纹芯材和面片以及夹紧端部之间的连接点出现了应力集中，从而产生了塑性变形，而这种变形很难在梁的整体大变形中反映出来。因此，本研究中捕捉到的金属波纹芯材夹层梁的动态晃动似乎并不完全，因此可称为 "明显的伪晃动"（危险潜伏在焊接点和夹紧端）。最后，基于简化的双线性硬化结构定律，从纯基材的角度进一步讨论了夹层梁动态晃动的内在机理。Journal of the Mechanics and Physics of SolidsPredicting the post-bifurcated patterns of architectured materials using group-theoretic toolsRachel Azulay, Christelle Combescuredoi:10.1016/j.jmps.2024.105631利用群论工具预测结构材料的分叉后模式Extensive studies on hexagonal honeycombs under in-plane compression have demonstrated that the structure’s symmetry plays a decisive part in the emergence of deformation patterns in post-bifurcated configurations. In this work, the aim is to take advantage of this property by presenting a new group-theoretic approach to list the various attainable post-bifurcated patterns of periodic architectured materials. As of today, some group-theoretic approaches have been elaborated for determining the post-bifurcated paths and thus patterns of a symmetric system submitted to specific loading conditions. However, the application of these approaches requires knowledge of the system’s governing equations. By making use of another group-theoretic tool, this work predicts the various possible post-bifurcated configurations of a periodic architectured material a priori of any non-linear computation by simply assessing the symmetry group of its undeformed configuration. This approach is applied, as an example, to the buckling of regular hexagonal honeycombs but can be easily transferred to any periodic architectured material. This work is a first step towards the elaboration of a more general process for the design of architectured materials when harnessing post-bifurcated behaviour is essential.对平面压缩下的六角蜂窝进行的大量研究表明，结构的对称性对分叉后配置变形模式的出现起着决定性作用。本研究旨在利用这一特性，提出一种新的群论方法，列出周期性结构材料的各种可实现的分叉后模式。迄今为止，已有一些群论方法用于确定对称系统在特定加载条件下的分叉后路径和模式。然而，应用这些方法需要了解系统的控制方程。本研究利用另一种群论工具，在进行任何非线性计算之前，只需评估周期性结构材料未变形构型的对称群，就能预测其各种可能的分叉后构型。例如，这种方法适用于规则六边形蜂窝的屈曲，但也可轻松应用于任何周期性结构材料。当利用分叉后行为至关重要时，这项工作是为设计建筑材料制定更通用流程迈出的第一步。Equilibrium analysis of surface-constrained elastic rods: Unveiling contact and internal forces through local geometryMeng Wang, Xin Yidoi:10.1016/j.jmps.2024.105635表面约束弹性杆的平衡分析：通过局部几何揭示接触力和内力Confinement scenarios of thin elastic rods are prevalent in both natural and engineered systems. The accurate quantification of the mechanical interplay between confined rods and their confining surfaces remains a formidable challenge, primarily due to the intricate nonlinear nature of thin rods and their contact with surfaces. Here, we present a theoretical framework designed to characterize the equilibrium states of thin elastic rods constrained to general surfaces, accounting for the influence of both conservative force and rod inhomogeneity. The framework proposes a general scheme to directly unveil contact and internal forces of confined rods through the consideration of local geometry, based on the balance equations for local forces and moments. Characteristics of the contact force are contingent upon whether the deformed rod exhibits vanishing geodesic curvature. Case studies involving closed rods constrained to spherical, cylindrical, and torus surfaces are conducted to elucidate geometric effects on various rod behavior, encompassing equilibrium configurations, internal forces and moments, and contact forces. The outcomes of our study offer fundamental insights into how geometric and material properties lead to the intricate mechanical interactions between one- and two-dimensional materials.在自然和工程系统中，薄弹性杆的约束情况非常普遍。主要由于细杆及其与表面接触的非线性性质错综复杂，准确量化受限杆及其受限表面之间的机械相互作用仍然是一项艰巨的挑战。在此，我们提出了一个理论框架，旨在描述受限于一般表面的薄弹性杆的平衡状态，同时考虑保守力和杆件不均匀性的影响。该框架基于局部力和力矩的平衡方程，提出了一种通用方案，通过考虑局部几何形状直接揭示约束杆的接触力和内力。接触力的特征取决于变形棒是否表现出消失的大地曲率。我们对受限于球面、圆柱面和环面的闭合杆进行了案例研究，以阐明几何对各种杆行为的影响，包括平衡构型、内力和力矩以及接触力。我们的研究成果从根本上揭示了几何和材料特性如何导致一维和二维材料之间错综复杂的机械相互作用。International Journal of PlasticityHigh-temperature “Inverse” Hall-Petch relationship and fracture behavior of TA15 alloyShaolong Li, Shufeng Li, Lei Liu, Huiying Liu, Chuanyun Wang, Philip J. Withers, Yuntian Zhu, Lina Gao, Shaodi Wang, Biao Chen, Wangtu Huo, Jianbo Gao, Xin Zhang, Bo Lidoi:10.1016/j.ijplas.2024.103951 TA15 合金的高温 "反 "霍尔-佩奇关系和断裂行为The Hall-Petch relationship is important for material design at room temperature. However, it is not well studied at high temperatures. In this work, the influence of different microstructures on the high-temperature mechanical behavior and corresponding softening mechanisms of high-temperature titanium alloy TA15 (Ti-6.5Al-2Zr-1Mo-1V, wt.%) were studied. Specimens with duplex, Widmanstätten, and coarse Widmanstätten microstructures were obtained through powder metallurgy. High-temperature tensile tests were carried out between 500-650℃. It was found that the fracture mode of the Widmanstätten microstructure was transgranular at 500°C and 550°C, but intergranular at 600°C and 650°C. EBSD analysis revealed that the high-temperature deformation was facilitated by several mechanisms including GB softening, GB migration, grains rotation, and activation of multiple slip systems. High temperature nanoindentation indicated sofenting of individual grains with increasing temperature. In-situ tensile testing under SEM revealed deformation was primarily in grain interior at room temperature, and GBs played a significant role at 650℃. The GB behavior at high temperatures is believed responsible for the inverse Hall-Petch relationship. These findings provide a new perspective for improving the high-temperature mechanical properties and microstructure control of titanium and its alloys.霍尔-佩奇关系对于室温下的材料设计非常重要。然而，在高温条件下，对它的研究并不深入。在这项工作中，研究了不同微结构对高温钛合金 TA15（Ti-6.5Al-2Zr-1Mo-1V，重量百分比）的高温力学行为和相应软化机制的影响。通过粉末冶金法获得了具有双相、维德曼斯泰滕和粗维德曼斯泰滕微观结构的试样。在 500-650℃ 之间进行了高温拉伸试验。结果发现，在 500°C 和 550°C 时，Widmanstätten 显微结构的断裂模式为透晶断裂，而在 600°C 和 650°C 时则为晶间断裂。EBSD 分析表明，高温变形是由多种机制促成的，包括 GB 软化、GB 迁移、晶粒旋转和多重滑移系统的激活。高温纳米压痕表明，随着温度的升高，单个晶粒会发生软化。在扫描电子显微镜下进行的原位拉伸测试表明，室温下的变形主要发生在晶粒内部，而在 650℃ 时，GB 起了重要作用。高温下的 GB 行为被认为是霍尔-佩奇反比关系的原因。这些发现为改善钛及其合金的高温机械性能和微观结构控制提供了新的视角。Thin-Walled StructuresAnti-penetration response and response mechanism of laminated structures made of different composite materials under impact loadXuanming Cai, Wei Zhang, Junyuan Wang, Zhiqiang Fan, Yubo Gao, Chenglong Pan, Heyang Sun, Zhujun Zhangdoi:10.1016/j.tws.2024.111840不同复合材料层压结构在冲击载荷下的抗穿透响应和响应机理Composite laminated structures are often subjected to high-speed impact from external objects in high impact environments, resulting in unpredictable forms of damage and even uncontrollable damage modes. To ensure the safety and reliability of these structures, research was conducted on the anti-penetration response and response mechanism of laminated structures made of different composite materials. Using carbon fiber reinforced plastic (CFRP) laminated structures and glass fiber/epoxy resin composite aluminum alloy (GLARE) laminated structures as research objects, a high-impact experimental setup was constructed based on a first-stage light gas gun to explore the relationship between the energy absorption characteristics and impact energy of composite laminates. Combined with the ballistic limit equations, the ballistic limit values of the composite laminated structures were determined, and the ballistic limits of the 2 mm thick CFRP laminated structure and the 2 mm thick GLARE laminated structure were 138.3 m/s and 215.6 m/s, respectively. The damage modes of CFRP laminated structure are mainly fiber fracture on the impact surface and fiber delamination, fiber tensile fracture and fiber bundle splitting on the back surface, while the damage modes of GLARE laminated structure are mainly plastic deformation, internal fiber fracture and crack extension at the penetration. At the same time, the cohesion unit is introduced to carry out numerical simulation research, which shows that the damage pore morphology of the cohesion unit between layers of composite laminated structures are closely related to their fiber layups, and the damage mode of cohesion unit between layers of composite laminated structures have been investigated, which reveals the damage mechanism in high-impact environments. The research results provide theoretical basis and common technical support for reverse design of composite laminated structures suitable for high impact environments.复合材料层压结构在高冲击环境下经常会受到外部物体的高速冲击，从而产生不可预测的破坏形式，甚至是不可控制的破坏模式。为了确保这些结构的安全性和可靠性，研究人员对不同复合材料制成的层压结构的抗穿透响应和响应机理进行了研究。以碳纤维增强塑料（CFRP）层压结构和玻璃纤维/环氧树脂复合铝合金（GLARE）层压结构为研究对象，构建了基于一级光气 枪的高冲击实验装置，以探索复合材料层压结构的能量吸收特性与冲击能量之间的关系。结合弹道极限方程，确定了复合材料层压结构的弹道极限值，2 毫米厚的 CFRP 层压结构和 2 毫米厚的 GLARE 层压结构的弹道极限值分别为 138.3 米/秒和 215.6 米/秒。CFRP层压结构的破坏模式主要是冲击面的纤维断裂和背面的纤维分层、纤维拉伸断裂和纤维束劈裂，而GLARE层压结构的破坏模式主要是塑性变形、内部纤维断裂和贯穿面裂纹扩展。同时，引入内聚单元进行数值模拟研究，结果表明复合材料层状结构层间内聚单元的损伤孔形态与其纤维铺层密切相关，并研究了复合材料层状结构层间内聚单元的损伤模式，揭示了高冲击环境下的损伤机理。研究成果为逆向设计适用于高冲击环境的复合材料层压结构提供了理论依据和共性技术支持。Design method for cross-section behaviour of hybrid I-girders under uniform bendingShuxian Chen, Jun-zhi Liu, Tak-Ming Chandoi:10.1016/j.tws.2024.111847均匀弯曲下混合工字梁截面行为的设计方法Hybrid steel I-girders, characterised by different strength grades for the flange and web, offer the potential to optimise material utilisation in various loading scenarios. The current American and European standards for steel bridges (AASHTO specification and Eurocode 3) have incorporated specific provisions for the design of hybrid I-girders with the web strength grade lower than the flange. Based on the data obtained from the validated numerical investigation, the limiting slenderness ratio for cross-section classification and applicability of the designated bending moment resistance (flexural strength) in standards are assessed. The assessment results reveal that the compact/Class 1 sections with flange yield strength of 690 N/mm2 fail to meet the current codified ductility requirement, and the non-compact flange slenderness limits in AASHTO specification are demonstrated to be excessively lenient. A reduction factor of 1.2 is suggested to narrow down the Class 1 width-to-thickness ratio in Eurocode 3 for I-girders with compression flange steel grade equivalent to S690. Furthermore, the design moment expression of the Direct Strength Method (DSM) is proposed for the cross-section resistance design of hybrid I-girders, and the analytical design approach for the Continuous Strength Method (CSM) is also derived through analytical analysis. Instead of addressing the slenderness of the flange and web individually, the DSM and CSM adopt the concept of overall cross-section slenderness, which allows for a more accurate consideration of the flange-web interaction and offers the potential to streamline the calculation process for cross-section resistance. The statistical and reliability analysis indicate that all the design methods could achieve the reasonable moment resistance predictions for the cross-section resistance of hybrid I-girders.混合工字钢梁的特点是翼缘和腹板的强度等级不同，这为在各种荷载情况下优化材料利用提供了可能。现行的美国和欧洲钢桥标准（AASHTO 规范和 Eurocode 3）对腹板强度等级低于翼缘的混合工字梁设计做出了具体规定。根据验证数值研究获得的数据，评估了截面分类的极限细长比和标准中指定的抗弯强度（抗弯强度）的适用性。评估结果表明，翼缘屈服强度为 690 牛/平方毫米的紧凑型/类别 1 断面无法满足当前编纂的延展性要求，而 AASHTO 规范中的非紧凑型翼缘细长率限制也被证明过于宽松。建议采用 1.2 的折减系数来缩小 Eurocode 3 中对采用与 S690 等级相当的压缩翼缘钢的工字钢的 1 级宽厚比。此外，还为混合工字梁的截面抗力设计提出了直接强度法（DSM）的设计力矩表达式，并通过分析得出了连续强度法（CSM）的分析设计方法。DSM 和 CSM 没有单独处理翼缘和腹板的细长度，而是采用了整体截面细长度的概念，这样可以更准确地考虑翼缘和腹板的相互作用，并有可能简化截面抗力的计算过程。统计和可靠性分析表明，所有设计方法都能对混合工字钢的截面抗力进行合理的抗弯矩预测。The rigid-flexible coupling vibration of assembled disk-composite conical shell structure of electric aircraft in hygrothermal circumstanceChenguang Wang, Xuyuan Song, Jian Zang, Yewei Zhang, Zhen Zhangdoi:10.1016/j.tws.2024.111823 湿热环境下电动飞机装配式圆盘复合锥壳结构的刚柔耦合振动A novel theoretical formulation for addressing the coupling vibration of the rigid disc and flexible composite conical shell structure (RDFCCSs) in hygrothermal circumstances is established to investigate the vibration evolution of the rigid-flexible composite thin-walled coupled structure of new energy electric aircraft. According to Donnell's thin shell theory, the potential energy of the composite conical shell under hygrothermal load is calculated. A uniform mass model and a set of artificial springs distributed on the interface of the shell and disk are imported to simulate the RDFCCSs. The governing equation of the RDFCCSs with arbitrary foundations in hygrothermal circumstances is deduced according to the Rayleigh-Ritz variational procedure. Systematic experiments and finite element simulations have been demonstrated to confirm the accuracy of the proposed method. Three new rigid-flexible coupling vibration modes of the RDFCCSs that differ from the traditional single thin-walled conical shell element due to the influence of the disk have been revealed. After that, the unique vibration characteristics of RDFCCSs under various masses, axial loads, hygrothermal environments and interface connection stiffnesses are discussed in detail.针对新能源电动飞机刚柔复合材料薄壁耦合结构在湿热环境下的耦合振动问题，建立了一种新的理论公式，研究了该结构的振动演化过程。根据 Donnell 薄壳理论，计算了复合材料锥壳在湿热载荷作用下的势能。为模拟 RDFCCS，导入了一个均匀质量模型和一组分布在壳体和圆盘界面上的人工弹簧。根据 Rayleigh-Ritz 变分过程，推导出了具有任意地基的 RDFCCS 在湿热环境下的控制方程。系统实验和有限元模拟证实了所提方法的准确性。由于圆盘的影响，RDFCCS 的三个新刚柔耦合振动模式与传统的单一薄壁锥壳元素有所不同。随后，详细讨论了 RDFCCS 在不同质量、轴向载荷、湿热环境和界面连接刚度下的独特振动特性。Experiments and modelling of competitive failure behaviour of CFRP stepped-lap repairs with different design parametersXiao Han, Mengting Hu, Yangyang Wang, Bo Liu, Lucas F.M. da Silva, Xu Guodoi:10.1016/j.tws.2024.111836不同设计参数下 CFRP 阶梯式修补的竞争性失效行为实验与建模Stepped-lap bonding has been preferably applied in composite repairing. Nevertheless, the design of repairs presents challenges due to the complex failure mechanism. This paper aims to investigate the mechanical performance and failure mechanism of Carbon Fibre Reinforced Polymer (CFRP) repairs with stepped-lap under tensile loading. Two design parameters are studied, i.e. step numbers and slope combinations. Furthermore, the two configuration methods two different configuration methods of Cohesive Zone Model are creatively employed in the developed numerical models, i.e. the adhesive interface adopts cohesive contact, while zero-thickness cohesive elements are inserted in the interlayer between the first two plies of CFRP to simulate possible delamination. Simulations are verified against experimental failure loads, as well as damage evolutions in the repaired adhesive interface, ply interlayer and CFRP laminate. Results showed that the tensile strength of stepped-lap repairs increased with step numbers. The three-step stepped-lap repair with a slope combination of 1/20-1/20-1/20 bears the strongest tensile strength and greatest load-bearing capacity. This work reveals the competitive failure mechanism in adhesively repaired composites and offers a reliable prediction approach for the design of bonded CFRP repairs in practical aeronautic applications.在复合材料修复中，阶梯搭接粘接技术得到了广泛应用。然而，由于失效机理复杂，修复设计面临着挑战。本文旨在研究碳纤维增强聚合物（CFRP）修复体在拉伸载荷下的机械性能和失效机理。本文研究了两个设计参数，即台阶数和坡度组合。此外，在开发的数值模型中创造性地采用了内聚区模型的两种配置方法，即粘合界面采用内聚接触，而在 CFRP 前两层之间的夹层中插入零厚度内聚元素，以模拟可能出现的分层。模拟结果与实验破坏载荷以及修复后的粘合剂界面、层间夹层和 CFRP 层压板的破坏演变进行了验证。结果表明，阶梯搭接修复的拉伸强度随着阶梯数的增加而增加。坡度组合为 1/20-1/20-1/20 的三步阶梯式修补具有最强的抗拉强度和最大的承载能力。这项研究揭示了粘合修复复合材料的竞争失效机理，为实际航空应用中的粘合 CFRP 修复设计提供了可靠的预测方法。A Methodology for Applying Isogeometric Inverse Finite Element Method to the Shape Sensing of Stiffened Thin-Shell StructuresEmiliano Del Priore, Luca Lampanidoi:10.1016/j.tws.2024.111837将等几何反有限元法应用于刚性薄壳结构形状传感的方法论The capability of reconstructing the displacement field of a structure based on in-situ strain measurements is referred to as “shape sensing” and constitutes a fundamental unit for the real-time monitoring of critical structural components. The Inverse Finite Element Method (iFEM) is one of the most promising innovative techniques for accomplishing this task. This study explores the application of iFEM in conjunction with Isogeometric Analysis (IGA) for the shape sensing of stiffened thin-shell structures. The use of IGA allows for the exact representation of computational geometry, simplifies mesh refinement, and potentially reduces the number of installed sensors. In the context of IGA, when the geometry of a structure is composed of multiple surfaces, non-conforming interfaces are typically involved. To overcome this issue, we propose an assembly process based on the Lagrange multiplier method to jointly apply iFEM and IGA to shell structures assemblies. The methodology is numerically validated using FEM models both to generate the in-situ strain data and as a comparison for iFEM reconstruction results. The case studies include a T-beam, a reinforced hyperbolic paraboloid, and a wingbox. Convergence analyses are performed to investigate the shape sensing accuracy as the number of inverse elements increases. Additionally, contour plots of displacement field components are compared with the reference solution, revealing a high degree of agreement.根据现场应变测量重建结构位移场的能力被称为 "形状传感"，是实时监测关键结构部件的基本单元。反有限元法（iFEM）是完成这一任务最有前途的创新技术之一。本研究探讨了 iFEM 与等几何分析 (IGA) 在刚化薄壳结构形状传感中的结合应用。使用 IGA 可以精确表示计算几何形状，简化网格细化，并有可能减少安装传感器的数量。在 IGA 的背景下，当结构的几何形状由多个表面组成时，通常会涉及不规则的界面。为了解决这个问题，我们提出了一种基于拉格朗日乘法的装配流程，将 iFEM 和 IGA 联合应用于壳体结构装配。我们使用有限元模型对该方法进行了数值验证，以生成原位应变数据，并与 iFEM 重建结果进行比较。案例研究包括 T 型梁、增强双曲抛物面和翼盒。随着反演元素数量的增加，进行了收敛分析，以研究形状传感精度。此外，还将位移场分量的等高线图与参考解进行了比较，结果显示两者高度一致。Effect of variable-thickness webs on shear buckling performance of welded steel plate girders: numerical analysis and proposed design rulesXiaoling Liu, Dongdong Xu, Yuanqing Wang, Boshan Chen, Huanxin Yuandoi:10.1016/j.tws.2024.111838变厚度腹板对焊接钢板梁剪切屈曲性能的影响：数值分析和建议的设计规则The use of welded steel members with varying thickness webs is becoming more popular and is often used as plate girders to accommodate varying loading distributions. Such variable-thickness steel plates are more susceptible to experiencing out-of-plane shear buckling, particularly in the thinner sections. However, no research work has been described investigating the shear buckling strength of welded steel plate girders with variable-thickness webs. This study presents an extensive numerical analysis to examine the shear buckling strength of such steel members with variable-thickness webs. Finite element (FE) models incorporating the material non-linearity and initial geometric imperfections were developed. To validate the modelling approach employed in this investigation, a total of 41 experimental results reported by the authors and other researchers were used. A detailed parametric study was subsequently undertaken, exploring various variables including local geometrical imperfections, aspect ratio, thickness change ratio, residual stress, and yield strength. To assess the accuracy of the current design regulations, the test and parametric study results were compared against design strengths. Upon comparison, the current design regulations as specified in Chinese Code (GB 50017), American Specification (ANSI/AISC 360-10) and Eurocodes (EN 1993-1-5) are over-conservative when computing the strength of such members with variable-thickness webs. Finally, new design rules covering both cases of variable-thickness and constant-thickness webs are proposed. A reliability analysis was conducted, and the values of β were 2.87, 3.00, and 3.04, respectively, indicating that new design methods developed in this study could closely determine the shear buckling strength of such welded steel plate girders with variable-thickness webs.使用不同厚度腹板的焊接钢构件正变得越来越流行，通常用作板梁，以适应不同的荷载分布。这种不同厚度的钢板更容易发生平面外剪切屈曲，尤其是在较薄的部分。然而，目前还没有关于变厚度腹板焊接钢板梁剪切屈曲强度的研究成果。本研究通过大量的数值分析来研究这种具有变厚度腹板的钢构件的剪切屈曲强度。研究开发了包含材料非线性和初始几何缺陷的有限元（FE）模型。为验证本研究中采用的建模方法，共使用了作者和其他研究人员报告的 41 项实验结果。随后进行了详细的参数研究，探讨了各种变量，包括局部几何缺陷、长宽比、厚度变化比、残余应力和屈服强度。为评估现行设计规定的准确性，将测试和参数研究结果与设计强度进行了比较。经比较，中国规范（GB 50017）、美国规范（ANSI/AISC 360-10）和欧洲规范（EN 1993-1-5）中规定的现行设计规定在计算此类具有变厚度腹板的构件强度时过于保守。最后，提出了涵盖变厚度和恒定厚度腹板两种情况的新设计规则。进行了可靠性分析，β 值分别为 2.87、3.00 和 3.04，表明本研究中开发的新设计方法可以准确确定变厚度腹板焊接钢板梁的剪切屈曲强度。Acoustic metasurface embedded with thin-walled plate based on phase modulation for multi-angle broadband sound absorptionJiahui Yan, Yingli Li, Yong Peng, Song Yaodoi:10.1016/j.tws.2024.111839 基于相位调制的嵌入薄壁板的声学元表面，用于多角度宽带吸声The design of low-frequency broadband acoustic absorbers with thin thicknesses is a long-standing and challenging problem. This work proposes an acoustic metasurface consisting of macro-perforated porous, thin-walled perforated plate, and meta-porous layers embedded by thin-walled plate (MPM) to combine the advantages of porous material and resonator. MPM is formed by four subunits with a phase gradient. The acoustic properties of an MPM unit cell are investigated by a theoretical model based on homogenization theory and transfer matrix methods, and the theoretical model is verified by a numerical model. Then, the sound absorption mechanism of MPM unit cell is explored, and it is revealed that the middle and low-frequency sound waves are mainly dissipated by thin-walled perforated plate and meta-porous layers, and the macro-perforated porous structure is aimed at the high-frequency absorption. In addition, the dependence of geometric parameters of MPM unit cell on acoustic performance and reflected phase is investigated. Furthermore, the geometric parameters of each subunit in acoustic metasurface are carefully designed, and excellent absorption in target frequency is obtained by the hybrid resonance of a single unit cell and the surface wave conversion of MPM with reflected phase gradient. Also, the appearance of perfect sound absorption comes from the far-field interference between reflected waves and the wave-trapping phenomenon near the periodic structure. A thin (λ/20) absorption panel MPMs is designed to achieve multi-angle low-frequency broadband absorption and an effective normal sound absorption (>50%) band over 344-3000 Hz. This work proposes a novel design idea and opens possibilities for acoustic metasurface practical applications in noise mitigation of various scenarios.设计厚度较薄的低频宽带吸声体是一个长期存在且极具挑战性的问题。本研究提出了一种由大穿孔多孔板、薄壁穿孔板和嵌入薄壁板的元多孔层组成的声学元表面（MPM），以结合多孔材料和谐振器的优点。MPM 由四个具有相位梯度的子单元组成。基于均质化理论和传递矩阵方法的理论模型研究了 MPM 单元的声学特性，并通过数值模型对理论模型进行了验证。然后，探讨了 MPM 单元室的吸声机理，发现中低频声波主要由薄壁穿孔板和元多孔层消散，而大穿孔多孔结构则主要针对高频吸声。此外，还研究了 MPM 单元的几何参数对声学性能和反射相位的影响。此外，还精心设计了声学元表面中每个子单元的几何参数，通过单个单元的混合共振和具有反射相位梯度的 MPM 表面波转换，获得了目标频率的优异吸声性能。此外，完美吸声的出现源于反射波之间的远场干涉和周期性结构附近的捕波现象。设计一种薄型（λ/20）吸声板 MPM，可实现多角度低频宽带吸声和 344-3000 Hz 有效正常吸声频段（>50%）。这项工作提出了一种新颖的设计理念，为声学元表面在各种场景的噪声缓解中的实际应用提供了可能性。Experimental and theoretical investigation into flexural performance of thin-walled steel-laminated bamboo lumber truss beamRui Ma, Xiaodun Wang, Yansheng Du, Guanghui Sun, Shao-Bo Kang, Jia Ma, Zhihua Chendoi:10.1016/j.tws.2024.111841薄壁钢层压竹材桁架梁抗弯性能的实验和理论研究This study presents a novel truss beam called thin-walled steel-laminated bamboo lumber truss beam (SBTB). The SBTB is composed of cold-formed thin-walled steel chords and laminated bamboo lumber web members. A total of 24 SBTBs were divided into eight groups, each group containing 3 specimens, to investigate various parameters, including bamboo web member thickness and laminated direction, number of self-drilling screws, shear span ratio, and truss beam height and width. The flexural performance of SBTBs was evaluated through a four-point bending test, analyzing the failure mode, deflection, bearing capacity, and bending stiffness. The impact of different parameters on the flexural performance was thoroughly examined and discussed. In addition, a theoretical model and simplified prediction approach for the bending stiffness of SBTBs were developed. The results identified five failure modes during the flexural tests and demonstrated the linear elastic and nonlinear stages of the SBTB working process. Increasing the width and height of the beam, the number of self-drilling screws, and adopting plain pressed laminated bamboo lumber web members significantly improved the bending resistance of the composite truss beam. Notably, the theoretical model accurately predicted the stiffness of SBTBs, with a maximum discrepancy of less than 12.3% between experimental and theoretical results.本研究提出了一种新型桁架梁，称为薄壁钢-层压竹材桁架梁（SBTB）。SBTB 由冷弯薄壁钢弦杆和层压竹材腹杆组成。总共 24 个 SBTB 被分成 8 组，每组 3 个试件，以研究各种参数，包括竹腹板构件厚度和层压方向、自钻螺钉数量、剪跨比、桁架梁高度和宽度。通过四点弯曲试验评估了 SBTB 的抗弯性能，分析了其破坏模式、挠度、承载力和弯曲刚度。对不同参数对弯曲性能的影响进行了深入研究和讨论。此外，还建立了 SBTB 弯曲刚度的理论模型和简化预测方法。结果确定了抗弯试验中的五种失效模式，并证明了 SBTB 工作过程中的线性弹性和非线性阶段。增加梁的宽度和高度、自钻螺钉的数量以及采用平压层压竹材腹杆，都显著提高了复合桁架梁的抗弯强度。值得注意的是，理论模型准确预测了 SBTB 的刚度，实验结果与理论结果之间的最大差异小于 12.3%。Transformable lattice with in-situ changeable elastic modulus arising from structural interactionNan Yang, Kunpeng Huang, Miao Zhao, Huaxian Weidoi:10.1016/j.tws.2024.111842由结构相互作用产生的具有原位可变弹性模量的可变形晶格Many efforts have been made for lattice design and fabrication for various applications, but most lattices possess fixed elastic modulus after fabrication, which impedes the development of multifunctional lattices. Here we propose a new lattice type that enables in-situ structural transformation and changeable elastic modulus. The structural interaction arises from opposite rotations of the rings from Yin and Yang patch of a lattice under compressive force. The distance between the Yin and Yang patch determines if interaction occurs and the lattice elastic modulus, which is decoupled with volume fraction. Here, numerical and experimental investigation were carried out to reveal the relationship between the interaction type, distance and stress-strain curve. Results show that the ratio of maximum to minimum elastic modulus of a lattice is 81.4 with six interaction bars on the ring, and we can obtain an exponential number of reprogrammable elastic moduli when combining multiple lattices as units to construct a cellular structure. Our work shows a potential for constructing intelligent lattices that can adapt to the surroundings.人们已经为晶格的设计和制造做出了很多努力，但大多数晶格在制造后具有固定的弹性模量，这阻碍了多功能晶格的发展。在此，我们提出了一种可实现原位结构转换和可变弹性模量的新型晶格。在压缩力的作用下，晶格的阴阳片环会发生相反的旋转，从而产生结构相互作用。阴阳片之间的距离决定了相互作用是否发生，也决定了晶格的弹性模量，而弹性模量则与体积分数脱钩。本文通过数值和实验研究揭示了相互作用类型、距离和应力应变曲线之间的关系。结果表明，在环上有六个相互作用条的情况下，晶格的最大弹性模量与最小弹性模量之比为 81.4，当以多个晶格为单元组合构建蜂窝结构时，我们可以获得指数数量的可重新编程的弹性模量。我们的工作显示了构建能适应周围环境的智能晶格的潜力。来源：复合材料力学仿真Composites FEM
