今日更新：International Journal of Solids and Structures 3 篇，Journal of the Mechanics and Physics of Solids 1 篇，Mechanics of Materials 1 篇，International Journal of Plasticity 2 篇，Thin-Walled Structures 2 篇International Journal of Solids and StructuresUniqueness of Finite Element Limit Analysis solutions based on weak form lower and upper bound methodsPoulsen Peter Noe, Olesen John Forbesdoi:10.1016/j.ijsolstr.2023.112532基于弱形式下限和上限方法的有限元极限分析解的唯一性Finite Element Limit Analysis (FELA) is increasingly used for calculating the ultimate bearing capacity of structures made of ductile materials. Within FELA for reinforced concrete structures the elements have been based on rigorous lower bound or boundary mixed formulations. The lower bound element formulation may be overly constrained for certain meshes and the dual displacement interpretation may contain spurious modes, moreover the boundary mixed element formulation has an internal equilibrium node with no associated displacement field. Here a consistent and general weak formulation based on virtual work is presented specifically for both the lower and the upper bound problem, and it is shown that they are each others dual ensuring uniqueness of the optimal solution. As a consequence there is no difference between the solutions based on the weak upper and lower bound methods. Here a plane element is presented, with a linear stress variation and a quadratic displacement field, optionally including a concentrated bar element with a linear variation of the normal force. These elements are applied in a verification example and two reinforced concrete examples where they show very good results for both load level, stress distribution and collapse mechanism even for coarse meshes.有限元极限分析（FELA）越来越多地用于计算韧性材料结构的极限承载力。在钢筋混凝土结构的有限元极限分析中，元素一直基于严格的下限或边界混合公式。对于某些网格来说，下限元素公式可能会限制过多，而且双重位移解释可能包含虚假模式，此外，边界混合元素公式有一个内部平衡节点，但没有相关的位移场。这里提出了一种基于虚拟工作的一致且通用的弱公式，特别适用于下边界问题和上边界问题，并证明它们互为对偶，确保了最优解的唯一性。因此，基于弱上界法和弱下界法的求解没有区别。这里介绍的是一种平面元素，具有线性应力变化和二次位移场，也可选择包含法向力线性变化的集中杆元素。这些元素被应用于一个验证实例和两个钢筋混凝土实例中，即使在粗网格中，它们也能在载荷水平、应力分布和坍塌机制方面显示出非常好的结果。Modelling deformation effects in multiple collisions using Collisional-SPHVyas Dhairya R., Cummins Sharen J., Delaney Gary W., Rudman Murray, Khakhar Devang V.doi:10.1016/j.ijsolstr.2023.112578利用碰撞-SPH 模拟多重碰撞的变形效应Multiple collisions of granules on a substrate are encountered in a wide range of applications. In this work, such multiple collisions are analysed using Collisional Smooth Particle Hydrodynamics (CSPH) to understand how deformation caused by an impact influences the collision dynamics of subsequent impacts. It is found that the collision dynamics depends on the location of the impact and the deformation of the substrate caused by the preceding impacts. The predictions of three theoretical models are also compared with CSPH to assess the accuracy of the assumptions made by the models. The theoretical model predictions are only found to be useful when the granule repeatedly impacts the same location. Since these models do not simulate the shape change during the substrate deformation they fail to accurately model the cases where multiple impacts occur at different locations.在各种应用中都会遇到颗粒在基底上发生多次碰撞的情况。在这项工作中，我们使用碰撞平滑粒子流体力学（CSPH）对这种多次碰撞进行了分析，以了解撞击造成的变形如何影响后续撞击的碰撞动力学。研究发现，碰撞动力学取决于撞击的位置和之前撞击造成的基体变形。还将三个理论模型的预测结果与 CSPH 进行了比较，以评估模型假设的准确性。结果发现，理论模型的预测只有在颗粒反复撞击同一位置时才有用。由于这些模型没有模拟基底变形过程中的形状变化，因此无法准确模拟在不同位置发生多次撞击的情况。Effect of the crack layer theory parameters on the discontinuous slow crack growth of high density polyethylene under fatigue loadingAlmomani Abdulla, Mourad Abdel-Hamid I., Deveci Suleymandoi:10.1016/j.ijsolstr.2023.112579裂纹层理论参数对疲劳载荷下高密度聚乙烯不连续慢速裂纹生长的影响For engineering thermoplastics, particularly high density polyethylene (HDPE), the crack layer (CL) theory is an effective proposition for modeling slow crack growth and predicting their lifetime. Nevertheless, the associated excessive input parameters needed in its implementation sets a difficulty for its use. Therefore, an understanding of the role of each parameter and how they affect the CL growth is needed. The effect of the parameters has been studied in the past, however, under creep conditions only. Their effects under other loading conditions, e.g., fatigue, and geometries, e.g., compact tension (CT) specimen, is still unclear. For instance, increasing the natural drawing ratio λ was found to non-linearly reduce failure time tf, whereas a rise in the drawing stress σdr increased tf which correlates logarithmically with the loading frequency f. Furthermore, tf was found to increase with the transformation energy γtr, specimen thickness B, plane stain elastic modulus E′, drawing stress σdr, characteristic time t∗, and the specific fracture energy γ0. Therefore, outcomes of this work extend the applicability of the CL theory in the design and lifetime prediction of various industrial products within oil and gas, nuclear, automotive, and aerospace.对于工程热塑性塑料，尤其是高密度聚乙烯（HDPE），裂纹层（CL）理论是模拟缓慢裂纹生长和预测其寿命的有效方法。然而，在实施过程中所需的相关输入参数过多，给其使用带来了困难。因此，需要了解每个参数的作用及其对 CL 生长的影响。过去对参数影响的研究仅限于蠕变条件下。它们在其他加载条件（如疲劳）和几何形状（如紧密拉伸 (CT) 试样）下的影响仍不清楚。例如，研究发现增加自然拉伸比 λ 会非线性地缩短破坏时间 tf，而拉伸应力 σdr 的增加会延长 tf，tf 与加载频率 f 成对数关系。此外，研究还发现 tf 会随着转化能 γtr、试样厚度 B、平面沾污弹性模量 E′、拉伸应力 σdr、特征时间 t∗ 和比断裂能 γ0 的增加而增加。因此，这项工作的成果扩展了 CL 理论在油气、核能、汽车和航空航天领域各种工业产品的设计和寿命预测中的适用性。Journal of the Mechanics and Physics of SolidsDynamic high-order buckling and spontaneous recovery of active epithelial tissuesWang Huan, Liu Yong-Quan, Hang Jiu-Tao, Xu Guang-Kui, Feng Xi-Qiaodoi:10.1016/j.jmps.2023.105496活性上皮组织的动态高阶屈曲和自发恢复Active epithelial tissues can adapt to quasi-static compressive forces through buckling instability, but their responses to dynamic forces at shorter timescales remain elusive. We firstly establish a cytoarchitectural model that can accurately capture the experimentally observed high-order buckling and postbuckling (e.g., spontaneous flattening and stress recovery) behaviors of epithelia under fast compression. It is found that the stress evolution of epithelia can be divided into three stages: loading, phase transition, and stress recovery. In the loading stage, we observe the high-order instability with a buckling mode highly correlated with the strain rate, and derive its analytical relation, showing that the rate-dependent buckling mode is quantitatively determined by the viscoelastic and geometrical characteristics of epithelia. In the phase transition and stress recovery stages, we demonstrate that the postbuckling process is governed by the active tension generated by the actomyosin network. Furthermore, by proposing a minimal model, we obtain the explicit solutions of the flattening time and stress recovery extent as functions of the applied strain or strain rate, which are in quantitative agreement with our simulations and relevant experiments. In addition, depending on the stress evolution route, we construct a universal phase diagram for the morphology evolution of the epithelia in a wide range of strain and strain rate. This study elucidates the dominative roles of the activity and rheological characteristics of active soft materials in their dynamic mechanical behaviors, offering an approach for studying the complex morphology evolution.活跃的上皮组织可以通过屈曲不稳定性来适应准静态压缩力，但它们对较短时标的动态力的反应仍然难以捉摸。我们首先建立了一个细胞结构模型，该模型能准确捕捉实验观察到的上皮组织在快速压缩下的高阶屈曲和屈曲后行为（如自发扁平化和应力恢复）。研究发现，上皮的应力演变可分为三个阶段：加载、相变和应力恢复。在加载阶段，我们观察到了与应变速率高度相关的屈曲模式的高阶不稳定性，并推导出了其分析关系，表明与速率相关的屈曲模式是由上皮的粘弹性和几何特性定量决定的。在相变和应力恢复阶段，我们证明了屈曲后过程是由肌动蛋白网络产生的主动张力控制的。此外，通过提出一个最小模型，我们得到了扁平化时间和应力恢复程度作为施加应变或应变率函数的显式解，这与我们的模拟和相关实验在数量上是一致的。此外，根据应力演化路径，我们还构建了一个通用相图，用于描述上皮在宽应变和应变率范围内的形态演化。这项研究阐明了活性软材料的活性和流变特性在其动态力学行为中的主导作用，为研究复杂的形态演变提供了一种方法。Mechanics of MaterialsA multi-scale approach to predict shrinkage and creep of cementitious composite in a hygro-thermo-chemo-mechanical framework-theoretical formulation and numerical validationPal Biswajit, Ramaswamy Ananthdoi:10.1016/j.mechmat.2023.104866在湿热-化学-力学框架下预测水泥基复合材料收缩和蠕变的多尺度方法--理论表述和数值验证Prediction of time-dependent deformation such as shrinkage and creep are of utmost interest in terms of long-term serviceability of a concrete structure. However, owing to highly heterogeneous nature of concrete, existing macroscopic prediction models lack in terms of its general applicability. Hence, in this study, a multi-scale description is used to simulate the shrinkage and creep of concrete where the heterogeneity and associated physical-chemical processes are modeled in a mathematical framework. A hierarchical homogenisation technique is used to link across different scales. Model predicated shrinkage and creep are then validated with the corresponding experimental data. Model prediction is also compared with few national codes and popular macroscopic models to highlights the associated gaps in these models that can be overcome with the present developed multi-scale approach.收缩和徐变等随时间变化的变形预测对混凝土结构的长期适用性至关重要。然而，由于混凝土具有高度异质性，现有的宏观预测模型缺乏普遍适用性。因此，本研究采用多尺度描述来模拟混凝土的收缩和徐变，并在数学框架内对异质性和相关的物理化学过程进行建模。分层均质化技术用于连接不同尺度。然后用相应的实验数据对模型预测的收缩和徐变进行验证。此外，还将模型预测与一些国家规范和流行的宏观模型进行了比较，以突出这些模型中的相关差距，而目前开发的多尺度方法可以克服这些差距。International Journal of PlasticityHeterogeneous metallic glass composites with a unique combination of strength, plasticity and conductivityBao Weizong, Bao Longke, Chen Jie, Li Junzhi, Xiang Tao, Yu Bohua, Cai Zeyun, Xie Guoqiangdoi:10.1016/j.ijplas.2023.103810 集强度、塑性和导电性于一身的异质金属玻璃复合材料Metallic glass-reinforced Cu-based composites offer a promising avenue for overcoming the trade-off between high strength and high electrical conductivity in materials. In this investigation, heterogeneous CuZrAl metallic glass-reinforced CuCrZr alloy composites are prepared through spark plasma sintering and a one-step hot pressing. The microstructural evolution of the composites during the preparation process and its correlation with mechanical and electrical properties are revealed. Grain refinement and dislocation accumulation in the CuCrZr alloy matrix resulted in strength gain and a trade-off in electrical conductivity. However, precipitation of the Cr-rich phase compensates for the loss of conductivity. Directional strengthening and toughening of the composites are achieved by inducing deformation of the CuZrAl metallic glass reinforcement in the undercooled liquid region to attain its ordered arrangement. Furthermore, the electrical and mechanical properties of the crystalline phase Cu10Zr7 at the edge of metallic glass are predicted and investigated using first-principles calculations, with a focus on its impact on the performance of composites. A novel Cu-based metallic glass composites fabricated using an efficient processing approach offers valuable insights into material selection for electrical conductor applications.金属玻璃增强铜基复合材料为克服材料中高强度和高导电性之间的权衡问题提供了一种前景广阔的途径。本研究通过火花等离子烧结和一步热压制备了异质 CuZrAl 金属玻璃增强 CuCrZr 合金复合材料。研究揭示了复合材料在制备过程中的微观结构演变及其与机械和电气性能的相关性。CuCrZr 合金基体中的晶粒细化和位错累积导致了强度的提高和导电性能的折衷。然而，富铬相的析出弥补了导电性的损失。通过在过冷液体区域诱导 CuZrAl 金属玻璃增强体变形，使其达到有序排列，从而实现了复合材料的定向增强和增韧。此外，还利用第一原理计算方法预测和研究了金属玻璃边缘结晶相 Cu10Zr7 的电气和机械特性，重点关注其对复合材料性能的影响。采用高效加工方法制造的新型铜基金属玻璃复合材料为电导体应用的材料选择提供了宝贵的见解。From mechanical behavior and elastocaloric effect to microscopic mechanisms of gradient-structured NiTi alloy: A phase-field studyZhang Qi, Chen Junyu, Fang Gangdoi:10.1016/j.ijplas.2023.103809 从梯度结构镍钛合金的机械行为和弹性效应到微观机制：相场研究The introduction of gradient structure has been recently reported as a practical way to tailor the mechanical behavior of NiTi while improving its elastocaloric effect simultaneously. In this research, a thermo-mechanically weakly coupled phase-field model considering crystal plasticity is employed to investigate the microscopic mechanisms of the elastocaloric effect related to the gradient structure, especially from the point of view of the two-way interaction between stress and martensite variants. A set of polycrystalline systems are established to accomplish the gradual transition from a fine-grained specimen to a coarse-grained one by the grain-size gradient. The gradually changed mechanical response and transformation characteristics during the superelastic simulations embody the effectiveness of the grain structure as a regulator of the material properties. The Brayton cycle simulations conducted next revolve around further validation of the proposed model and variant-related interpretation of the effects of the grain structure. Predictions relevant to histories of stress and temperature agree well with the experimental results, and more remarkably, the linear stress-temperature relationship observed during the stress drop of the first hold in the Brayton cycle conforms perfectly to the classical Clausius–Clapeyron relation. Together with martensite reorientation, the propagating martensite phases, where the increasing non-major variants are necessary complements to the major one preferentially aligned with the external stress, are largely responsible for this stress drop. Regarding the elastocaloric effect, the gradient structures achieve very similar cooling capacity but higher cooling efficiency compared to the coarse-grain one, taking advantage of more martensite, particularly the major variant, produced if provided with the same transformable area (excluding the grain boundaries). Besides, a steeper gradient in structures is prone to alter the composition of martensite variants and more non-major variants are demanded to alleviate the developing deformation mismatch among layers with different grain sizes.最近有报道称，引入梯度结构是调整镍钛机械行为并同时改善其弹性效应的一种实用方法。本研究采用考虑晶体塑性的热-机械弱耦合相场模型来研究与梯度结构相关的弹性效应的微观机制，特别是从应力和马氏体变体之间的双向相互作用的角度进行研究。建立了一组多晶系统，通过晶粒尺寸梯度完成从细粒试样到粗粒试样的渐变。超弹性模拟过程中逐渐变化的机械响应和转变特性体现了晶粒结构作为材料特性调节器的有效性。接下来进行的布雷顿循环模拟围绕着进一步验证所提出的模型以及对晶粒结构影响的变异相关解释展开。与应力和温度历史相关的预测与实验结果非常吻合，更值得注意的是，在布雷顿循环第一次保持应力下降期间观察到的线性应力-温度关系完全符合经典的克劳修斯-克拉皮隆关系。与马氏体重新取向一起，传播马氏体相（其中不断增加的非大变体是与外部应力优先对齐的大变体的必要补充）在很大程度上造成了这种应力下降。在弹性热效应方面，梯度结构与粗晶粒结构相比，冷却能力非常接近，但冷却效率更高，因为如果提供相同的可转变区域（不包括晶界），会产生更多的马氏体，尤其是主要变体。此外，较陡的梯度结构容易改变马氏体变体的组成，需要更多的非主要变体来缓解不同晶粒尺寸层之间正在形成的变形不匹配。Thin-Walled StructuresNet section tension capacity of high strength steel single shear bolted connectionsLin Xue-Mei, Yam Michael C.H., Song Yuchen, Chung Kwok-Fai, Ho Ho-Cheung, Han Yaweidoi:10.1016/j.tws.2023.111371高强度钢单剪切螺栓连接的净截面拉伸能力Single shear bolted connections under tension usually exhibit out-of-plane deformation due to the inherent load eccentricity, resulting in significant stress concentration around the bolt holes and a stress gradient through the plate thickness. This effect is particularly pronounced in high-strength steel (HSS) connections due to the relatively lower ductility and tensile-to-yield strength ratio of HSS. However, it remains unclear whether this issue can lead to premature fracture in high strain regions before effective stress redistribution develops across the net section, subsequently reducing the ultimate load capacity of the HSS connections. To examine the above design issue, an experimental and numerical study on single shear bolted connections was conducted and reported in this paper. A total of 25 connections were tested, among which 17 were made of HSS (Q690 and Q960), and 8 were made of Q345 mild steel (MS). Based on a validated finite element (FE) model, a comprehensive numerical analysis was carried out to interpret the structural behaviour of the specimens and explore the influence of various design parameters on the ultimate tension capacity of single shear bolted connections. The findings revealed that, despite the existence of out-of-plane deformation in the steel plate, all connections (either MS or HSS) investigated in this study reached the theoretical net section resistance (the product of the net section area and the ultimate tensile strength). This is because (1) the relatively low ductility and tensile-to-yield strengths ratio of HSS materials are still sufficient to allow an effective stress redistribution across both the transverse net section and the plate thickness, and (2) the biaxial stress state around the bolt holes enhances the tension capacity of the net section. Finally, a statistical evaluation of the combined test and numerical data showed that the existing design equations for predicting the net section tension capacity of HSS (specified in EN 1993-1-12:2007 and prEN 1993-1-1:2020) can be safely applied to the design of HSS single shear bolted connections, even in scenarios where the tensile-to-yield strengths ratio of HSS is as low as 1.06.拉伸状态下的单剪切螺栓连接通常会因固有的负载偏心而产生平面外变形，从而导致螺栓孔周围出现明显的应力集中和板厚的应力梯度。由于高强度钢（HSS）的延展性和拉伸与屈服强度比相对较低，因此这种效应在高强度钢（HSS）连接中尤为明显。然而，目前仍不清楚这一问题是否会导致在净截面上形成有效的应力再分布之前，高应变区域过早断裂，从而降低高速钢连接的极限承载能力。为研究上述设计问题，本文对单剪切螺栓连接进行了实验和数值研究，并在文中进行了报告。共测试了 25 个连接件，其中 17 个由高速钢（Q690 和 Q960）制成，8 个由 Q345 低碳钢（MS）制成。在经过验证的有限元（FE）模型的基础上，进行了全面的数值分析，以解释试样的结构行为，并探讨各种设计参数对单剪切螺栓连接的极限拉伸能力的影响。研究结果表明，尽管钢板存在平面外变形，但本研究中的所有连接（MS 或 HSS）都达到了理论净截面阻力（净截面面积与极限抗拉强度的乘积）。这是因为：(1) 高速钢材料的延展性和抗拉强度与屈服强度之比相对较低，但仍足以在横向净截面和钢板厚度上实现有效的应力再分布；(2) 螺栓孔周围的双轴应力状态增强了净截面的抗拉能力。最后，对综合测试和数值数据的统计评估表明，现有的预测高速钢净截面拉伸能力的设计方程（EN 1993-1-12:2007 和 prEN 1993-1-1:2020）可以安全地应用于高速钢单剪切螺栓连接的设计，即使在高速钢的拉伸强度与屈服强度比低至 1.06 的情况下也是如此。Energy absorption of a bio-inspired cylindrical sandwich structureHa Ngoc San, Lee Ting-Uei, Ma Jiaming, Li Jie, Xie Yi Mindoi:10.1016/j.tws.2023.111378受生物启发的圆柱形夹层结构的能量吸收This research investigates the energy absorption capability of a new bio-inspired cylindrical sandwich structure (BCSS). The sandwich core of the BCSS is designed to mimic the skeletal system of deep-sea glass sponge, which has a square lattice architecture reinforced by diagonal bracings. In this study, energy absorption characteristics are numerically evaluated, with results compared to those of conventional cylindrical sandwich structures with typical lattice and foam cores. It is found that the BCSS has significantly higher energy absorption capacity. In detail, the specific energy absorption of the BCSS is 31.2%, 18.1% and 24.4% higher than those of conventional cylindrical sandwich structures with the kagome, square and foam cores, respectively. Furthermore, a parametric study is performed which reveals that the cell number and the wall thickness of both the core and the skins are key factors determining the energy absorption capacity of the BCSS. Finally, a theoretical derivation is developed to conveniently predict the mean crushing force of the BCSS. This research sheds light on using biomimetic approaches to design an advanced composite structure with high energy absorption efficiency.本研究探讨了一种新型生物启发圆柱夹层结构（BCSS）的能量吸收能力。BCSS 的夹层核心是模仿深海玻璃海绵的骨架系统设计的，它具有由对角支撑加固的方格结构。在这项研究中，对能量吸收特性进行了数值评估，并将结果与具有典型晶格和泡沫夹芯的传统圆柱形夹层结构进行了比较。结果发现，BCSS 的能量吸收能力明显更高。具体而言，BCSS 的比能量吸收能力分别比采用卡格姆、方形和泡沫芯材的传统圆柱形夹层结构高出 31.2%、18.1% 和 24.4%。此外，参数研究表明，芯材和表皮的单元数和壁厚是决定 BCSS 能量吸收能力的关键因素。最后，通过理论推导，可以方便地预测 BCSS 的平均压碎力。这项研究揭示了如何利用仿生方法来设计具有高能量吸收效率的先进复合材料结构。来源：复合材料力学仿真Composites FEM
