今日更新：Journal of the Mechanics and Physics of Solids 1 篇，International Journal of Plasticity 1 篇，Thin-Walled Structures 1 篇Journal of the Mechanics and Physics of SolidsTime-dependent constitutive behaviors of a dynamically crosslinked glycerogel governed by bond kinetics and chain diffusionJi Lin, Md. Tariful Islam Mredha, Rumesh Rangana Manimel Wadu, Chuanqian Shi, Rui Xiao, Insu Jeon, Jin Qiandoi:10.1016/j.jmps.2024.105951由键动力学和链扩散控制的动态交联甘油凝胶的时间相关本构行为Soft materials featuring dynamic networks represent a burgeoning frontier in materials science, offering multifaceted applications spanning soft robotics, biomaterials, and flexible electronics. Unraveling the time-dependent constitutive behavior of these materials, rooted in dynamic networks, stands as a pivotal pursuit for engineering advancements. Herein, we fabricate a tough and extreme-temperature-tolerant glycerogel with a polymer network crosslinked by metal-coordination crosslinkers and conduct a thorough analysis of its intricate mechanical responses across monotonic loading, relaxation, creep, and cyclic tests. We then develop a physically grounded constitutive model integrating the dynamics of crosslinker association/dissociation and polymer chain diffusion, furnishing a holistic framework to elucidate their interplay. We employ a statistical description, using density functions of chains in terms of end-to-end vectors, to characterize network reconfiguration. The evolution of chain density under external load, mediated by crosslinker kinetics and chain diffusion in a viscous medium, leads to intriguing variations in elastic energy and stress responses. Through meticulous experimental validation and numerical simulations, we demonstrate the efficacy of the model in forecasting the mechanical behavior of dynamic polymer networks under diverse loading scenarios, encompassing strain rate effects, stress relaxation, Mullins effect, and self-recovery phenomena. Our findings provide valuable insights into the design and optimization of dynamic network-based materials for diverse applications in biomedical and engineering fields.具有动态网络特征的软材料代表了材料科学的新兴前沿，提供了涵盖软机器人、生物材料和柔性电子的多方面应用。揭示这些材料的时间依赖本构行为，根植于动态网络，是工程进步的关键追求。在此，我们制造了一种坚韧和耐极端温度的甘油凝胶，其聚合物网络由金属配位交联剂交联，并通过单调加载、松弛、蠕变和循环测试对其复杂的力学响应进行了彻底的分析。然后，我们开发了一个基于物理的本构模型，该模型集成了交联剂结合/解离和聚合物链扩散的动力学，提供了一个整体框架来阐明它们的相互作用。我们采用统计描述，使用链的密度函数在端到端矢量，以表征网络重构。外载荷下链密度的演变，由交联剂动力学和链在粘性介质中的扩散介导，导致弹性能量和应力响应的有趣变化。通过细致的实验验证和数值模拟，我们证明了该模型在预测动态聚合物网络在不同加载场景下的力学行为方面的有效性，包括应变率效应、应力松弛、Mullins效应和自恢复现象。我们的发现为动态网络材料的设计和优化在生物医学和工程领域的各种应用提供了有价值的见解。International Journal of PlasticityA novel cobweb-like sub-grain structured Al-Cu-Mg alloy with high strength-plasticity synergyYufeng Song, Qin Zhang, Heng Li, Xudong Yuan, Yuqiang Chen, Dingding Lu, Wenhui Liudoi:10.1016/j.ijplas.2024.104178 一种具有高强塑性协同作用的网状亚晶Al-Cu-Mg合金Al-Cu-Mg alloys, as the most widely used lightweight structural materials, have been recognized as promising candidates in the transportation field for a low-carbon economy. However, the tensile strength and plasticity of alloys cannot be simultaneously improved to satisfy the requirements of continuously upgraded transportation vehicles. In this work, inspired by high-tensile strength and high plasticity of cobweb structure, a novel cobweb-like sub-grain structure was developed in Al-Cu-Mg alloys by a successive solution, high-strain-rate rolling (4.4 s-1), cryogenic treatment (–196°C) and aging process (SRCA). Notably, the tensile strength and plasticity of this alloy were superior to those reported in the current study. An ultrahigh Vickers hardness and tensile strength value of 206.2 Hv and 619.6 MPa, which were 39.8% and 31.8% higher than those of traditional T6 heat-treated Al-Cu-Mg alloys, were obtained after SRCA. Meanwhile, an increase in the elongation of this alloy from 4.31% to 8.23% (increase of 90.9%) was also achieved. More importantly, the high strength-plasticity (“double high”) Al-Cu-Mg alloy was attributed to a cobweb-like sub-grain structure, which was proposed for the first time by utilizing reverse thinking to enhance plasticity through elevating dislocations, due to the formation of high-density dislocations from high-strain-rate rolling and rearrangement effect of dislocations from cryogenic treatment. Furthermore, the strength-plasticity mechanism was verified using in-situ tensile electron back scatter diffraction (EBSD), molecular dynamics (MD) simulations, and crystal plasticity (CP) models. The results indicated that the cobweb-like sub-grain structure, resembling countless walls, formed barriers that hindered dislocation migration towards high-angle grain boundaries (HAGBs) and absorbed them, thereby reducing the occurrence of stress concentration zones, i.e., the dislocation absorption and stress-strain sharing mechanisms. Additionally, the strengthening mechanism was associated with synergistic strengthening by multiscale microstructures, including micron-sized grains, micron-sized high-density dislocation lattices, and nanosized Al2CuMg phases, which were activated by successive deformation processes. Consequently, the concept of biomimetic structure design, which may serve as an effective method for achieving structural materials with high strength-plasticity synergy, can be extended to transportation fields, such as railway tracks and body structure design.铝铜镁合金作为应用最广泛的轻质结构材料，在低碳经济的交通运输领域具有广阔的应用前景。然而，合金的抗拉强度和塑性不能同时提高，以满足不断升级的运输车辆的要求。本研究以蛛网组织的高抗拉强度和高塑性为灵感，通过连续固溶、高应变速率轧制（4.4 s-1）、低温处理（-196°C）和时效处理（SRCA），在Al-Cu-Mg合金中形成了一种新型的蛛网状亚晶组织。值得注意的是，该合金的抗拉强度和塑性优于目前报道的。经SRCA处理的Al-Cu-Mg合金的维氏硬度和抗拉强度分别为206.2 Hv和619.6 MPa，分别比传统的T6热处理Al-Cu-Mg合金高39.8%和31.8%。同时，合金的伸长率也从4.31%提高到8.23%，提高了90.9%。更重要的是，Al-Cu-Mg合金的高强度塑性（“双高”）归因于蛛网状亚晶结构，这是首次利用逆向思维通过提高位错来提高塑性，这是由于高应变速率轧制形成高密度位错和低温处理产生的位错重排效应。此外，利用原位拉伸电子背散射衍射（EBSD）、分子动力学（MD）模拟和晶体塑性（CP）模型验证了强度-塑性机理。结果表明：网状亚晶结构如同无数壁，形成屏障，阻碍位错向高角晶界迁移并吸收它们，从而减少了应力集中区的发生，即位错吸收和应力-应变分担机制。此外，强化机制与多尺度微观结构的协同强化有关，包括微米尺寸的晶粒、微米尺寸的高密度位错晶格和纳米尺寸的Al2CuMg相，这些微观结构在连续变形过程中被激活。因此，仿生结构设计的概念可以扩展到交通运输领域，如铁路轨道和车身结构设计，作为实现结构材料高强度-塑性协同的有效方法。Thin-Walled StructuresExperimental and analytical investigation on the shear behaviour of a demountable interlocking connection applied in precast floor diaphragmsPeng CHEN, Jiachen GUO, Tak-Ming CHANdoi:10.1016/j.tws.2024.112696应用于预制楼板隔板的可拆卸联锁连接抗剪性能的试验与分析研究Traditional web connections in precast floor diaphragms adopt cast-in-situ or field welding techniques, which pose significant challenges for the disassembly and reuse of floor slabs. This paper introduces an innovative demountable interlocking web connection that relies on neither traditional welding nor bolting methods, with greatly improved assembly and disassembly efficiencies. Besides, multiple shear connectors can be installed in one go to reduce installation time compared with bolted connection. To assess the in-plane interaction behaviour between shear connectors and embedded steel plates, as well as to evaluate the reusability of this new web connection, a comprehensive experimental investigation was conducted through monotonic loading tests. Results indicated that the proposed web connection exhibited excellent force transmission capabilities, and effectively transferred shear forces through the deformation of the shear connectors. By using faceplates made of high-strength steel, the shear damage was efficiently limited to the connectors, which can be easily demounted and reinstalled to allow the slab to be reused. Additionally, the results also showed that increasing the number of shear keys did not impair the normalised shear resistance per connector but could greatly improve the installation efficiency. Finite element analysis was carried out to further investigate the parameters that influence the connection performance of the proposed web connection. Design recommendations were proposed based on parametric results to predict the in-plane shear resistance of this innovative demountable interlocking web connection.传统的预制楼板腹板连接采用现浇或现场焊接技术，这对楼板的拆卸和再利用构成了重大挑战。本文介绍了一种新型的可拆卸联锁腹板连接，它既不依赖传统的焊接方法，也不依赖传统的螺栓连接方法，大大提高了装配和拆卸效率。此外，与螺栓连接相比，多个剪切连接件可一次安装，缩短了安装时间。为了评估剪切连接件与预埋钢板之间的平面内相互作用行为，以及评估这种新型腹板连接的可重用性，通过单调加载试验进行了全面的试验研究。结果表明：所提出的腹板连接具有良好的传力能力，可通过剪力连接件的变形有效传递剪力。通过使用由高强度钢制成的面板，有效地将剪切损伤限制在连接器上，连接器可以很容易地拆卸和重新安装，从而使面板可以重复使用。此外，结果还表明，增加剪切键的数量不会影响每个连接器的正态抗剪能力，但可以大大提高安装效率。通过有限元分析，进一步研究了影响网络连接性能的参数。基于参数化结果提出了设计建议，以预测这种创新的可拆卸联锁腹板连接的面内抗剪能力。来源：复合材料力学仿真Composites FEM
