今日更新:International Journal of Solids and Structures 1 篇,Journal of the Mechanics and Physics of Solids 1 篇,International Journal of Plasticity 1 篇,Thin-Walled Structures 3 篇
Developing a scalable analytical framework for predicting the contact behavior of elastic rings against rigid surfaces
Zhipeng Liu, Jaehyung Ju
doi:10.1016/j.ijsolstr.2024.112967
开发可扩展的分析框架,用于预测弹性环与刚性表面的接触行为
An elastic ring interacting with rigid surfaces is a fundamental engineering challenge with vast practical implications in various disciplines. However, the exploration of closed-form solutions for this issue has been limited, and existing studies often present complex, numerically unstable solution methods influenced by specific boundary conditions. Furthermore, the lack of scalable design principles for the ring-in-contact scenario has hindered its broader application across different geometries and materials. This study introduces a streamlined analytical and numerical approach to predict the contact behavior of orthotropic rings against centrosymmetric rigid surfaces, encompassing both flat and curved surfaces. Our approach, which simplifies the closed-form solution for extensible Timoshenko curved beams coupled with a contact algorithm that prevents penetration, yields robust and accurate predictions of nonlinear contact behaviors in elastic rings, including deformation patterns, contact angles, stresses, and stiffness. Additionally, we present a design map that serves as a scalable guideline for engineering elastic rings in contact, facilitating the choice of geometry and materials, such as ring radius, thickness, and elastic moduli. This research enhances the theoretical underpinnings of elasticity concerning ring contact and expands the engineering viewpoint on designing elastic rings in various contact scenarios.
弹性环与刚性表面相互作用是一项基本的工程挑战,对各学科具有广泛的实际影响。然而,对这一问题的闭式求解方法的探索还很有限,现有的研究往往提出了受特定边界条件影响的复杂、数值不稳定的求解方法。此外,接触环缺乏可扩展的设计原则,阻碍了其在不同几何形状和材料中的广泛应用。本研究介绍了一种简化的分析和数值方法,用于预测各向同性环与中心对称刚性表面(包括平面和曲面)的接触行为。我们的方法简化了可伸展季莫申科曲线梁的闭式解法,并结合了防止穿透的接触算法,可对弹性环的非线性接触行为进行稳健而准确的预测,包括变形模式、接触角、应力和刚度。此外,我们还提出了一个设计图,作为工程设计接触弹性环的可扩展指南,便于选择几何形状和材料,如环半径、厚度和弹性模量。这项研究加强了弹性环接触的理论基础,并拓展了在各种接触情况下设计弹性环的工程视角。
Quantifying 3D time-resolved kinematics and kinetics during rapid granular compaction, Part I: Quasistatic and dynamic deformation regimes
Sohanjit Ghosh, Mohmad M. Thakur, Ryan C. Hurley
doi:10.1016/j.jmps.2024.105765
量化快速颗粒压实过程中的三维时间分辨运动学和动力学,第一部分:准静态和动态变形机制
Impacts in granular materials occur over a velocity range of a few hundred m/s in manufacturing processes to several km/s during asteroid impacts. Different energy dissipation mechanisms are activated during impacts based on the kinetic energy of the impactor and the properties of the granular material. Material response during impact can be classified into two broad regimes – quasi-static and dynamic – characterized by the nature of grain and pore deformation and the deformation morphology of grain interfaces. In the quasi-static regime, all energy from the impactor is utilized in pore (or void) collapse, while in the dynamic regime, excess energy after pore closure leads to material melting or jetting and often to non-planar grain interfaces. To understand the transition between the quasi-static and dynamic regimes, in-situ measurements of temperature, local stresses, and porosity at the grain scale are critical but often not possible due to short timescales and inherent heterogeneity of granular materials. In this work, we use X-ray phase contrast imaging (XPCI) to visualize grain-scale deformation during rapid granular compaction and observe phenomena such as plastic flow-induced pore collapse, compaction wave propagation, and the morphology of the grain-grain interfaces. Alongside these experiments, we develop and validate a mesoscale numerical model that incorporates each sample’s microstructure and captures realistic plasticity and thermal effects. Using this validated model, we quantify the temperatures, pressures, and porosity as granular materials are compacted in both quasi-static and dynamic deformation regimes. By comparing our results with existing theoretical models, we find that the continuum definitions of quasi-static and dynamic regimes needs to be updated for a realistic heterogeneous granular media. Specifically, the two regimes can coexist in the same assembly of grains at different time instants due to spatial heterogeneity and rapid dissipation of impact energy away from the point of impact. Finally, we quantify the energies associated with different dissipation mechanisms for individual grains using coupled numerical and analytical techniques. Our methodology allows us to obtain full 3D kinematics and kinetics of rapidly compacted granular materials at both the mesoscale and the grain scale.
颗粒材料的撞击速度范围从制造过程中的几百米/秒到小行星撞击时的几千米/秒。根据撞击器的动能和颗粒材料的特性,撞击过程中会启动不同的能量消散机制。撞击过程中的材料响应可分为准静态和动态两大类,其特征在于颗粒和孔隙变形的性质以及颗粒界面的变形形态。在准静态条件下,来自冲击器的所有能量都被孔隙(或空隙)塌陷所利用,而在动态条件下,孔隙闭合后的多余能量会导致材料熔化或喷射,通常会导致晶粒界面不平整。要了解准静态和动态状态之间的转变,对温度、局部应力和晶粒尺度的孔隙率进行现场测量至关重要,但由于时间尺度短和颗粒材料固有的异质性,这往往是不可能的。在这项工作中,我们利用 X 射线相衬成像 (XPCI) 对快速颗粒压实过程中的颗粒尺度变形进行可视化,并观察塑性流动引起的孔隙塌陷、压实波传播和颗粒-颗粒界面形态等现象。在进行这些实验的同时,我们还开发并验证了一个中尺度数值模型,该模型结合了每个样品的微观结构,并捕捉到了真实的塑性和热效应。利用这个经过验证的模型,我们对颗粒材料在准静态和动态变形状态下压实时的温度、压力和孔隙率进行了量化。通过将我们的结果与现有的理论模型进行比较,我们发现准静态和动态状态的连续定义需要针对现实的异质颗粒介质进行更新。具体来说,由于空间异质性和撞击能量在远离撞击点时的快速消散,这两种状态可以在不同的时间时刻共存于同一个颗粒集 合体中。最后,我们利用数值和分析耦合技术量化了与单个晶粒的不同耗散机制相关的能量。我们的方法使我们能够在中尺度和颗粒尺度上获得快速压实颗粒材料的全三维运动学和动力学。
Operative slip systems and their critical resolved shear stresses in η-Fe2Al5 investigated by micropillar compression at room temperature
Zhenghao Chen, Tsukasa Horie, Xiaofeng Wang, Haruyuki Inui
doi:10.1016/j.ijplas.2024.104057
室温下通过微柱压缩研究η-Fe2Al5中的工作滑移系统及其临界解析剪应力
The plastic deformation behavior of single crystals of orthorhombic η-Fe2Al5 has been investigated by micropillar compression at room temperature as a function of crystal orientation and specimen size. Plastic flow is observed even at room temperature by the operation of six slip systems; (001)<010>, (001)<110>, (001)<130>, {2 2 ¯ 3}<110>, {311}< 1 ¯ 03> and {301}< 1 ¯ 03>. The CRSS values for the five identified slip systems are very high all in the range of 1.1∼1.5 GPa and do not vary much with specimen size. In the middle of the stereographic projection, the (001)<010>, (001)<110>, (001)<130> and {2 2 ¯ 3}[110] slip systems operate according to the relative Schmid factors with the similar CRSS values in the range of 1.08∼1.23 GPa. In orientations close to [001], the {311}< 1 ¯ 03> slip system as well as the {301}< 1 ¯ 03> slip system operate with a much higher CRSS values around 1.5 GPa, producing wavy slip traces due to the occurrence of frequent cross-slip among these slip planes. In orientations close to the [100]-[110]-[010] symmetry line, on the other hand, premature failure occurs without the operation of any slip systems, although, the Schmidt factor-wise, the {311}< 1 ¯ 03> and {301}< 1 ¯ 03> slip systems could operate. The selection of slip systems, their CRSS values and the possible dislocation dissociation modes are discussed based on the overlapped atomic volume that occurs during shear along the slip direction on the slip plane, taking into account the partial occupancies of Al atoms in the linear atomic chain along the orthorhombic c-axis direction.
通过微柱压缩研究了室温下正交η-Fe2Al5 单晶体的塑性变形行为与晶体取向和试样尺寸的关系。即使在室温下,通过六种滑移系统的操作也能观察到塑性流动:(001)<010>, (001)<110>, (001)<130>, {2 2 ¯ 3}<110>, {311}< 1 ¯ 03> 和 {301}< 1 ¯ 03>。五个已识别滑移系统的 CRSS 值都非常高,在 1.1∼1.5 GPa 范围内,且随试样尺寸变化不大。在立体投影的中间位置,(001)<010>、(001)<110>、(001)<130>和{2 2 ¯3}[110]滑移系统根据相对施密德因子运行,CRSS 值在 1.08∼1.23 GPa 范围内相似。在靠近[001]的方向上,{311}< 1 ¯ 03>滑移系统和{301}< 1 ¯ 03>滑移系统的CRSS值在1.5 GPa左右,由于这些滑移面之间经常发生交叉滑移,因此会产生波浪形滑移痕迹。另一方面,在靠近[100]-[110]-[010]对称线的方向上,虽然从施密特因子来看,{311}< 1 ¯ 03>和{301}< 1 ¯ 03>滑移系统可以工作,但在没有任何滑移系统工作的情况下会发生过早失效。根据沿滑移面上的滑移方向剪切时发生的重叠原子体积,并考虑到沿正菱形 c 轴方向线性原子链中铝原子的部分占有率,讨论了滑移系统的选择、其 CRSS 值和可能的位错解离模式。
Functionally graded foam materials for head impact protection
Shunfeng Li, Q.M. Li, Kwong Ming Tse, Tong Pang
doi:10.1016/j.tws.2024.112193
用于头部撞击保护的功能分级泡沫材料
Head injuries commonly result from impact accidents, underscoring the urgent requirement for enhanced helmet protection. Functionally graded foam (FGF) materials present promising avenues for augmenting the design of impact-attenuating liners in helmets, thereby mitigating head injuries. This study aims to investigate the performance of the FGF materials in protecting against head frontal impact and provide an effective optimization methodology to support the efficient and reliable design of the FGF materials. The foam finite element model was developed and coupled with a highly biofidelic head model to simulate the FGF-head frontal impact scenarios. A parametric study based on the coupled FGF-head model was conducted to explore the effects of the configuration parameters on the protection performance of the FGF materials. The study demonstrated that the negative-gradient FGF materials provide better head impact protection than the uniform density foam (UDF) and positive-gradient FGF materials, despite the potential disadvantage in energy absorption. A discrete optimization method based on the FGF-head model was developed and illustrated to efficiently achieve an optimized design for FGF protectability, thereby reducing the risk of head injuries. The optimized design reduced the Head Injury Criterion (HIC) value by 40.4% compared to the conventional UDF design, from 1660 to 990. Therefore, this study provides a further understanding and a new optimization insight into designing FGF materials to improve head impact protection.
撞击事故通常会导致头部受伤,因此迫切需要加强头盔保护。功能分级泡沫(FGF)材料为增强头盔内撞击衰减衬垫的设计,从而减轻头部伤害提供了广阔的前景。本研究旨在探讨泡沫塑料在保护头部免受正面撞击方面的性能,并提供有效的优化方法来支持泡沫塑料的高效可靠设计。该研究开发了泡沫有限元模型,并将其与高生物保真度的头部模型相结合,以模拟 FGF-头部正面撞击情景。在耦合 FGF 头部模型的基础上进行了参数研究,以探索配置参数对 FGF 材料防护性能的影响。研究表明,与均匀密度泡沫(UDF)和正梯度 FGF 材料相比,负梯度 FGF 材料在能量吸收方面具有潜在的劣势,但却能提供更好的头部撞击保护。基于 FGF-头部模型开发并说明了一种离散优化方法,可有效实现 FGF 保护性的优化设计,从而降低头部受伤的风险。与传统的 UDF 设计相比,优化设计将头部伤害标准(HIC)值降低了 40.4%,从 1660 降至 990。因此,这项研究为设计 FGF 材料以改善头部撞击保护提供了进一步的理解和新的优化见解。
Compressive behaviour and capacities of S690 high strength steel welded π-shaped and cruciform section stub columns
Qianzhi Chen, Lulu Zhang, Ou Zhao
doi:10.1016/j.tws.2024.112194
S690 高强度钢焊接π形和十字形截面支柱的抗压性能和承载能力
This paper reports experimental and numerical investigations into the cross-sectional behaviour and resistances of S690 high strength steel welded π-shaped and cruciform section stub columns under compression. An experimental investigation was firstly carried out on five S690 high strength steel welded π-shaped sections and five S690 high strength steel welded cruciform sections (covering both non-slender and slender sections) and included material tensile coupon tests, initial local geometric imperfection measurements and twenty stub column tests. The experimental investigation was supplemented by a numerical modelling investigation, where finite element models were firstly developed to simulate test structural responses and subsequently adopted to conduct parametric studies to generate further numerical data. On the basis of the obtained experimental and numerical data, the relevant design rules for high strength steel welded sections under compression, as set out in the European code, American specification and Australian standard, were assessed. The assessment results indicated that (i) the European code and American specification led to overall accurate and consistent cross-section compression resistance predictions for S690 high strength steel welded π-shaped sections, but provided slightly conservative and scattered resistance predictions for their cruciform section counterparts, and (ii) the Australian standard was accurate and consistent when used for non-slender S690 high strength steel welded π-shaped sections, but the design resistances were conservative and scattered for slender S690 high strength steel welded π-shaped sections as well as non-slender and slender S690 high strength steel welded cruciform sections.
本文报告了对 S690 高强度钢焊接 π 形截面和十字形截面桩柱在受压情况下的截面行为和阻力进行的实验和数值研究。首先对五个 S690 高强度钢焊接 π 形截面和五个 S690 高强度钢焊接十字形截面(包括非细长截面和细长截面)进行了实验研究,包括材料拉伸试样测试、初始局部几何缺陷测量和二十次存根柱测试。实验研究还辅以数值建模研究,首先开发了有限元模型来模拟试验结构响应,随后采用有限元模型进行参数研究,以生成进一步的数值数据。根据获得的实验和数值数据,对欧洲规范、美国规范和澳大利亚标准中规定的受压高强度钢焊接型材的相关设计规则进行了评估。评估结果表明:(i) 欧洲规范和美国规范对 S690 高强度钢焊接 π 形截面的横截面抗压性预测总体上准确且一致,但对十字形截面的抗压性预测略显保守且分散;以及 (ii) 澳大利亚标准对 S690 高强度钢焊接 π 形截面的横截面抗压性预测总体上准确且一致,但对十字形截面的抗压性预测略显保守且分散、(ii) 澳大利亚标准用于非细长 S690 高强度钢焊接 π 型截面时准确一致,但用于细长 S690 高强度钢焊接 π 型截面以及非细长和细长 S690 高强度钢焊接十字型截面时,设计阻力保守且分散。
Numerical investigation and design methods of the local buckling of WAAM stainless steel circular hollow section stub columns
Yanan Huang, Lu Yang, Meiyu Liu, Kelong Xu
doi:10.1016/j.tws.2024.112195
WAAM 不锈钢圆形空心截面支柱局部屈曲的数值研究和设计方法
3D printing is an advanced technology that has been used in biomedical and automotive engineering, and has raised a significant response in civil engineering. Wire and arc additive manufacturing (WAAM), a metal 3D printing technology, has prospective applications in steel construction because it can fabricate large-scale structural members at an acceptable cost and manufacturing efficiency. Fundamental studies are still urgently needed to realise its engineering application. However, due to the irregular geometric features, limited studies on the structural performance of WAAM components, particularly the numerical studies, have been carried out. To this end, a numerical investigation on the local buckling of WAAM stainless steel circular hollow section (CHS) stub columns under axial compression has been conducted and presented herein. The finite element (FE) models were established and validated against the existing experimental research. Parametric studies were subsequently carried out to broaden the cross-sectional resistance data pool using the developed FE models. The applicability of the cross-section design provisions specified in EN 1993-1-4:2006+A2:2020, ANSI/AISC 370-21 and the continuous strength method (CSM) for the design of WAAM CHS was evaluated according to the experimental and FE results. Furthermore, a modified design method with improved accuracy was suggested.
3D打印是一种先进技术,已在生物医学和汽车工程领域得到应用,并在土木工程领域引起了巨大反响。线弧增材制造(WAAM)是一种金属3D打印技术,在钢结构领域具有广阔的应用前景,因为它可以以可接受的成本和制造效率制造大型结构件。要实现其工程应用,仍迫切需要进行基础研究。然而,由于其不规则的几何特征,对 WAAM 构件结构性能的研究,尤其是数值研究十分有限。为此,本文对 WAAM 不锈钢圆形空心截面 (CHS) 存根柱在轴向压缩下的局部屈曲进行了数值研究。根据现有的实验研究建立并验证了有限元 (FE) 模型。随后进行了参数研究,以利用开发的 FE 模型扩大横截面阻力数据池。根据实验和 FE 结果,评估了 EN 1993-1-4:2006+A2:2020、ANSI/AISC 370-21 和连续强度法 (CSM) 中规定的截面设计条款对 WAAM CHS 设计的适用性。此外,还提出了一种精度更高的改进设计方法。