Zhai Chongpu, Albayrak Nahuel, Engqvist Jonas, Hall Stephen A, Wright Jonathan, Majkut Marta, Herbold Eric B, Hurley Ryan C
State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi'an Jiaotong University, Xi'an, China and Department of Mechanical Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA.
Hopkins Extreme Materials Institute, Johns Hopkins University, Baltimore, Maryland 21218, USA.
Phys Rev E. 2022 Jan;105(1-1):014904. doi: 10.1103/PhysRevE.105.014904.
Quantifying the ways in which local particle rearrangements contribute to macroscopic plasticity is one of the fundamental pursuits of granular mechanics and soft matter physics. Here we examine local rearrangements that occur naturally during the deformation of three samples of 3D granular materials subjected to distinct boundary conditions by employing in situ x-ray measurements of particle-resolved structure and stress. We focus on five distinct rearrangement measures, their statistics, interrelationships, contributions to macroscopic deformation, repeatability, and dependence on local structure and stress. Our most significant findings are that local rearrangements (1) are correlated on a scale of three to four particle diameters, (2) exhibit volumetric strain-shear strain and nonaffine displacement-rotation coupling, (3) exhibit correlations that suggest either rearrangement repeatability or that rearrangements span multiple steps of incremental sample strain, and (4) show little dependence on local stress but correlate with quantities describing local structure, such as porosity. Our results are presented in the context of relevant plasticity theories and are consistent with recent findings suggesting that local structure may play at least as important of a role as local stress in determining the nature of local rearrangements.
量化局部颗粒重排对宏观塑性的贡献方式是颗粒力学和软物质物理学的基本研究方向之一。在此，我们通过对颗粒分辨结构和应力进行原位X射线测量，研究了在不同边界条件下三种三维颗粒材料样品变形过程中自然发生的局部重排。我们关注五种不同的重排度量、它们的统计特性、相互关系、对宏观变形的贡献、可重复性以及对局部结构和应力的依赖性。我们最显著的发现是，局部重排：（1）在三到四个颗粒直径的尺度上具有相关性；（2）表现出体积应变 - 剪切应变以及非仿射位移 - 旋转耦合；（3）表现出的相关性表明重排具有可重复性，或者重排跨越了样品应变增量的多个步骤；（4）对局部应力的依赖性很小，但与描述局部结构的量（如孔隙率）相关。我们的结果是在相关塑性理论的背景下呈现的，并且与最近的研究结果一致，这些研究结果表明在确定局部重排的性质方面，局部结构可能至少与局部应力起着同样重要的作用。
