今日更新:International Journal of Solids and Structures 1 篇,Mechanics of Materials 1 篇,International Journal of Plasticity 1 篇,Thin-Walled Structures 1 篇
Meso-scale size effects of material heterogeneities on crack propagation in brittle solids: Perspectives from phase-field simulations
Liuchi Li, Jack Rao, Todd C. Hufnagel, K.T. Ramesh
doi:10.1016/j.ijsolstr.2024.112795
材料异质性对脆性固体裂纹扩展的中尺度尺寸效应:相场模拟的视角
Brittle solids are often toughened by adding a second-phase material. This practice often results in composites with material heterogeneities on the meso scale: large compared to the scale of the fracture process zone but small compared to that of the application. The specific configuration (both geometrical and mechanical) of this mesoscale heterogeneity is generally recognized as important in controlling crack propagation behavior and, subsequently, the (effective) toughness of the composite. Here, we systematically investigate how dynamic brittle fracture navigates through a linear array of mesoscale inclusions. Using a variational phase-field (PF) approach, we compute the apparent crack speed and fracture energy dissipation rate to compare crack propagation (and the resulting toughening) under Mode-I loading for various configurations of inclusions. We identify an interplay between the size of inclusion and that of the K-dominant zone in the presence of elastic heterogeneity: matching these two sizes gives rise to the best toughening outcome for a given area fraction of inclusions. We discuss mechanisms that rationalize this observation and the importance of the length scale parameter used in PF models in interpreting simulation results. Our work sheds physical insight into the interaction between size effects and material properties, thereby opening a venue for the rational design of functional (architected) composites for dynamic fracture applications.
脆性固体通常通过添加第二相材料来增韧。这种做法通常会导致复合材料具有中观尺度的材料异质性:与断裂过程区域的尺度相比较大,但与应用的尺度相比较小。人们普遍认为这种中尺度异质性的具体结构(包括几何结构和机械结构)对于控制裂纹扩展行为以及复合材料的(有效)韧性非常重要。在此,我们系统地研究了动态脆性断裂是如何穿过中尺度夹杂物的线性阵列的。利用变分相场 (PF) 方法,我们计算了表观裂纹速度和断裂能量耗散率,以比较各种夹杂物配置在模式 I 加载下的裂纹扩展(以及由此产生的韧性)。我们发现,在存在弹性异质性的情况下,夹杂物的尺寸与 K 主导区的尺寸之间存在相互作用:对于给定面积分数的夹杂物,匹配这两种尺寸可获得最佳增韧结果。我们讨论了使这一观察结果合理化的机制,以及 PF 模型中使用的长度尺度参数对解释模拟结果的重要性。我们的研究揭示了尺寸效应与材料特性之间相互作用的物理原理,从而为动态断裂应用中功能(结构)复合材料的合理设计开辟了道路。
Macroscopic elasticity of the hat aperiodic tiling
Romain Rieger, Alexandre Danescu
doi:10.1016/j.mechmat.2024.104988
帽子非周期性平铺的宏观弹性
In this paper, we explore the macroscopic elastic behavior of the aperiodic but hyperuniform ein stein (single tile) tiling, as recently reported in Smith et al. (2023a, 2023b). The first step involves assigning mechanical properties to the geometric pattern. The simplest approach includes near-neighbor type (NN) interactions (springs) along the edges of the geometric pattern. To eliminate zero modes, we also incorporate angular interactions using the simplest quadratic approximation—the Kirkwood-Keating three-body potential. We compute the macroscopic elastic response on circular domains for various realizations across an increasing sequence of length scales. As the domain radius increases, the set average at a fixed length scale of the obtained macroscopic Hooke tensor approaches the hyperplane of two-dimensional isotropic Hooke tensors. In a closer-to-experiment scenario, we also discuss a second mechanical setting where edges of all polygons in the considered domain are treated as one-dimensional continua (straight beams). These continua are endowed with both extension/compression, shear and bending energy within the framework of the Timoshenko theory. The macroscopic response of the hat tiling aligns with that of an isotropic elastic continuum.
在本文中,我们探讨了非周期性但超均匀的 ein Stein(单瓦)平铺的宏观弹性行为,最近 Smith 等人(2023a, 2023b)对此进行了报道。第一步是为几何图案分配机械属性。最简单的方法包括沿几何图案边缘的近邻型(NN)相互作用(弹簧)。为了消除零模式,我们还使用最简单的二次近似--Kirkwood-Keating 三体势能--纳入了角度相互作用。我们计算了圆形畴上的宏观弹性响应,其实现方式多种多样,长度尺度序列不断增加。随着畴半径的增加,获得的宏观胡克张量在固定长度尺度上的集 合平均值接近二维各向同性胡克张量的超平面。在更接近实验的情况下,我们还讨论了第二种力学设置,即把考虑域中所有多边形的边缘视为一维连续体(直梁)。在季莫申科理论的框架内,这些连续体被赋予了拉伸/压缩、剪切和弯曲能量。帽形平顶的宏观响应与各向同性弹性连续体的宏观响应一致。
STZ-Clay: A shear-transformation-zone theory based constitutive model for clay
W.L. Li, N. Guo, Z.X. Yang
doi:10.1016/j.ijplas.2024.103958
STZ-粘土:基于剪切-变形区理论的粘土构成模型
The shear-transformation-zone (STZ) theory is a mesoscale-based approach that attributes material macroscopic plastic deformation to the flipping, creation, and annihilation of mesoscopic structures known as STZs. In this study, the potential of the STZ theory in soil constitutive modeling is demonstrated through the development of a model coined STZ-Clay, by extending the conventional STZ theory to incorporate two essential characteristics of clay, i.e., plastic volumetric strain and pressure dependence. The STZ-Clay model assumes that the plastic volumetric strain arises from the creation and annihilation of STZs, while the pressure-dependency is accounted for by the dissipation rate function and evolution law of two internal variables, namely STZ density and orientational bias. Remarkably, the STZ-Clay model achieves a unique critical state under different loading paths and reasonably reproduces the influence of consolidation history on the hardening and dilatancy of clay. Overall, the STZ-Clay model offers a fresh perspective for understanding the yielding mechanism and critical state of clay through the lens of mesostructural evolution.
剪切变形区(STZ)理论是一种基于中观尺度的方法,它将材料的宏观塑性变形归因于被称为 STZ 的中观结构的翻转、创建和湮灭。在本研究中,通过扩展传统的 STZ 理论,将粘土的两个基本特征(即塑性体积应变和压力依赖性)纳入其中,建立了一个被称为 STZ-Clay 的模型,从而证明了 STZ 理论在土壤组成模型中的应用潜力。STZ-Clay 模型假定塑性体积应变来自 STZ 的产生和湮灭,而压力依赖性则由两个内部变量(即 STZ 密度和取向偏差)的耗散率函数和演化规律来解释。值得注意的是,STZ-Clay 模型在不同加载路径下实现了独特的临界状态,并合理地再现了固结历史对粘土硬化和膨胀的影响。总之,STZ-Clay 模型为从介观结构演化的角度理解粘土的屈服机制和临界状态提供了一个全新的视角。
Generalized beam theory for the analysis of thin-walled structures—A state-of-the-art survey
Christian Mittelstedt
doi:10.1016/j.tws.2024.111849
用于薄壁结构分析的广义梁理论--最新研究成果
Thin-walled prismatic metallic members as well as structures made of laminated composite materials are routinely employed in engineering branches such as civil engineering or lightweight construction and design. Due to their thin-walled nature, such structures exhibit a number of specific characteristics that need to be taken into account during analysis and design. One of these special features is the tendency to exhibit an interaction of local, global and distortional deformation patterns which has a major impact on the structural response in the framework of first-order analysis, but also concerning the buckling, postbuckling and vibration behavior of such structures. One analysis method that takes such effects into account in a natural and straightforward way is the so-called Generalized Beam Theory (GBT), and this paper aims at providing an overview of the state of the art in this specific field. In all, 460 references are cited.
薄壁棱柱金属构件以及由层压复合材料制成的结构通常用于土木工程或轻质结构和设计等工程领域。由于其薄壁特性,此类结构表现出许多特殊特征,需要在分析和设计过程中加以考虑。其中一个特点是容易表现出局部、整体和扭曲变形模式的相互作用,这不仅对一阶分析框架内的结构响应有重大影响,而且对此类结构的屈曲、后屈曲和振动行为也有重大影响。所谓的广义梁理论(GBT)是一种以自然和直接的方式考虑到这些影响的分析方法,本文旨在概述这一特定领域的技术现状。本文共引用了 460 篇参考文献。