今日更新:International Journal of Solids and Structures 1 篇,International Journal of Plasticity 1 篇,Thin-Walled Structures 2 篇
A comprehensive investigation of the lattice structure mechanical properties based on schwarz primitive triply periodic minimal surface: Elastic modulus, yield strength, and maximum bearing force in the elastic region
Amin Dadashi, Gholamhossein Rahimi
doi:10.1016/j.ijsolstr.2024.112776
基于施瓦茨基元三周期极小面的晶格结构力学特性综合研究:弹性区域的弹性模量、屈服强度和最大承载力
Due to ongoing investigations, the potential for using triply periodic minimal surface (TPMS) lattice structures in various industries has been increased. The analytical relationships that determine the mechanical properties of these structures make cost-effective designs achievable for designers. In this study, a comprehensive investigation that includes analytical, numerical, and experimental approaches to determine the mechanical properties of the Primitive triply periodic minimal surface (P-TPMS) lattice structure under unidirectional loading was performed. The innovation of this paper is the derivation of analytical relationships of mechanical properties, including elastic modulus, yield strength, and maximum load-bearing force in the elastic region in terms of geometrical parameters of Primitive unit cell and properties of the constituent materials. These mechanical properties were obtained using the energy method and Euler-Bernoulli beam theory for relative densities in the range of 0.24–0.76. Relative density was determined based on the geometric parameter of the surface size (m). In addition, the lattice structures were fabricated additively manufactured, and compressive test experiments were conducted. The mechanical properties of P-TPMS lattice structures vary dramatically with varying surface size values, according to the study's findings. The P-TPMS lattice structure's elastic modulus and yield strength at m=0.35 are more than 11 and 32 times larger, respectively than the yield stress and elastic modulus at m=0.65. The unit cell's length has no bearing on the elastic modulus or yield strength.
随着研究的不断深入,三重周期性最小表面(TPMS)晶格结构在各行各业的应用潜力不断增加。确定这些结构机械性能的分析关系使得设计人员可以进行经济有效的设计。本研究通过分析、数值和实验等方法对原始三周期极小面(P-TPMS)晶格结构在单向载荷下的力学性能进行了全面研究。本文的创新之处在于根据原始单元格的几何参数和组成材料的特性,推导出机械特性的分析关系,包括弹性模量、屈服强度和弹性区域的最大承载力。这些力学性能是在相对密度为 0.24-0.76 的范围内,利用能量法和欧拉-伯努利梁理论获得的。相对密度是根据表面尺寸(m)的几何参数确定的。此外,还采用添加法制造了晶格结构,并进行了抗压测试实验。研究结果表明,随着表面尺寸值的变化,P-TPMS 晶格结构的机械性能也会发生显著变化。m=0.35 时,P-TPMS 晶格结构的弹性模量和屈服强度分别比 m=0.65 时的屈服应力和弹性模量大 11 倍和 32 倍以上。单元格的长度对弹性模量和屈服强度没有影响。
Exceptional ductility through interface-constrained grain growth for the ultrafine-scale Ni/Ni-W layered composites
Fei Liang, Zhe-Xuan Wang, Mei-Yue Li, Bin Zhang, Xue-Mei Luo, Xiao-Fei Zhu, Guang-Ping Zhang
doi:10.1016/j.ijplas.2024.103959
通过界面约束晶粒生长实现超细镍/镍-钨层状复合材料的优异延展性
Enhancing the strength of metallic laminates through decreasing the constituent layer thickness from micrometer to nanometer scale is usually accompanied by the degradation of ductility because plastic instability characterized by fatal shear bands inevitably occurs in the early stage of deformation. To overcome the strength-ductility trade-off dilemma, we designed a kind of metallic layered composites (LCs) consisting of nano-grained Ni (grain size: 21-37 nm) and ultrafine nano-grained Ni-W (grain size: 8 nm) constituent layers with layer thickness ranging from microns to tens of nanometers. We found that the strength and ductility of Ni/Ni-W LCs can be simultaneously enhanced by decreasing the layer thickness. Interface-constrained grain growth in the Ni layers with an initial layer thickness of less than 1 μm enhances strain hardening ability. Thus, strain delocalization characterized by the formation of rectangular strain zones instead of crossed micro shear bands appears in the LCs. Based on the above mechanism, we obtained the optimum ratio of the layer thickness to the grain size for the nano-grained Ni layers as about 15:1, which corresponds to Ni0.25/Ni-W0.025 LCs with the highest tensile strength (1.9 GPa) and elongation to failure (5.5%). These findings may provide a new path for the design principle of metallic LCs with multi-level microstructural and geometrical scales.
通过将组成层的厚度从微米级减小到纳米级来提高金属层压材料的强度,通常会伴随着延展性的降低,因为在变形早期不可避免地会出现以致命剪切带为特征的塑性不稳定性。为了克服强度-延展性权衡的难题,我们设计了一种由纳米级镍(晶粒尺寸:21-37 纳米)和超细纳米级镍-钨(晶粒尺寸:8 纳米)组成的金属层状复合材料(LCs),层厚从微米到数十纳米不等。我们发现,通过减小层厚度,Ni/Ni-W LCs 的强度和延展性可同时得到提高。初始层厚小于 1 μm 的镍层中的界面约束晶粒生长可增强应变硬化能力。因此,低密度层中出现了以形成矩形应变区而不是交叉微剪切带为特征的应变分散。根据上述机理,我们得到了纳米晶粒镍层的最佳层厚与晶粒大小比约为 15:1,对应于具有最高拉伸强度(1.9 GPa)和破坏伸长率(5.5%)的 Ni0.25/Ni-W0.025 LCs。这些发现可能会为具有多级微结构和几何尺度的金属 LCs 的设计原理提供一条新的途径。
WELDED BEAM-TO-COLUMN STEEL JOINTS: ASSESSMENT OF EUROPEAN DESIGN RULES
Jorge Conde, Fernando Freire, Filip Ljubinković, Martin Vild, Luís Simões da Silva
doi:10.1016/j.tws.2024.111844
梁与柱的焊接钢接头:欧洲设计规则评估
Properly validated high-quality Finite Element (FE) models with experimental tests permit an accurate description of the load-deformation path and stress state of steel joints and are nowadays accepted as “experimental results”. Changes to the design of welded joints in Eurocode 3 are currently proposed that affect the resistance and stiffness of the components associated with the column web panel. This paper presents an assessment of the design formulations included in the current Eurocode 3, part 1-8, and its forthcoming update in terms of stiffness and moment resistance, compared against a large parametric study of strong-axis beam-column welded joints for open sections carried out using validated sophisticated FE models. The results show that both the old and new Eurocode formulations provide a large scatter and no big differences between both methods. Additionally, the presence of axial force in the column shows a clear increase in the ratio between design resistance vs numerical resistance that, particularly in the case of transversally stiffened joints, may be unconservative.
经过适当验证的高质量有限元 (FE) 模型与实验测试可以准确描述钢接头的载荷变形路径和应力状态,如今已被公认为 "实验结果"。目前,欧洲规范 3 对焊接接头的设计提出了修改建议,这将影响与柱腹板相关部件的阻力和刚度。本文介绍了对现行 Eurocode 3 第 1-8 部分及其即将更新的刚度和抗弯矩设计方案的评估,并与使用经过验证的复杂 FE 模型对开放截面的强轴梁-柱焊接接头进行的大型参数研究进行了比较。研究结果表明,新旧欧洲规范的计算方法存在较大差异,两种方法之间没有明显区别。此外,柱中轴向力的存在明显增加了设计阻力与数值阻力之间的比率,特别是在横向加固接头的情况下,这可能是不可靠的。
Experimental and numerical investigation of through-diaphragm in H-shaped steel beam to CFST column connections
YongHyun Cho, Fangying Wang, SooYeon Seo, KangSeok Lee, TaeSoo Kim
doi:10.1016/j.tws.2024.111852
H 型钢梁与 CFST 柱连接中贯穿隔膜的实验和数值研究
This research proposes a cruciform through-diaphragm (CTD) for an H-shaped steel beam to concrete-filled steel tubular (CFST) column and investigates its seismic performance experimentally and numerically. The proposed connection consists of through-plates passing through the aligned slots in the panel zone and end plates directly welded to an H-shaped steel beam. This connection eliminates welding inside the steel tube for installation of the diaphragm, while providing a reliable load path from the steel beam to the CFST column. The experimental program examined the connection hysteretic behaviors, including the moment-rotation response, ductility, initial stiffness, and energy dissipation capacity. The proposed connection shows stable hysteric behavior and good energy dissipation up to a story drift up to 4% and satisfies the AISC seismic provisions criteria for special moment connection. A finite element (FE) model was established and verified against the experimental results. The effects of concrete infill, steel tube column thickness, axial load ratio, and through-plate thickness on the hysteretic behavior of the proposed connection were investigated through parametric analysis of 24 FE models. This study provides the information on the optimized design parameters that ensures the stable seismic performance of the proposed connection that could be used in structural engineering practice.
本研究提出了一种用于 H 型钢梁与混凝土填充钢管(CFST)柱的十字形贯穿隔膜(CTD),并对其抗震性能进行了实验和数值研究。拟议的连接由穿过面板区对齐槽的通板和直接焊接到 H 型钢梁上的端板组成。这种连接方式省去了在钢管内焊接安装隔膜的工序,同时提供了从钢梁到 CFST 柱的可靠载荷路径。实验程序检查了连接的滞后行为,包括力矩旋转响应、延展性、初始刚度和耗能能力。拟议的连接显示出稳定的滞回行为和良好的消能能力,可承受高达 4% 的楼层漂移,并满足 AISC 抗震规定中关于特殊弯矩连接的标准。建立了一个有限元(FE)模型,并根据实验结果进行了验证。通过对 24 个有限元模型进行参数分析,研究了混凝土填充、钢管柱厚度、轴向荷载比和通板厚度对拟议连接滞回行为的影响。这项研究提供了优化设计参数的信息,以确保所提连接具有稳定的抗震性能,可用于结构工程实践。