Micro-granular Mechanics for Deformation and Failure of Granular Materials

以前的研究表明，通常的应变概念(第一位移梯度)不能很好地描述大偏差加载条件下颗粒材料的破坏前后行为。在这项研究中，将探索使用附加运动学描述符的概念，而不是通常的应变概念。这项工作的总体目标是使用新的运动学描述符来发展微观颗粒力学理论，以便这些理论适用于整个应力-变形行为范围。所采用的方法将基于微观-宏观方法，其中组件的行为与颗粒的性质相关联。实验数据和计算机模拟将成为理论发展的一个组成部分。发展的细颗粒力学理论将在有限元环境中实现。通过比较颗粒材料在不同加载条件下的实测和预测行为，验证了该模型的有效性。这一研究结果将为连续介质力学中材料局部化和分叉的理论框架提供洞察。在局部化破坏区域起主要作用的材料的固有长度将直接与细观结构相关。这一独特的特征显著地将该理论与基于现象学的模型区分开来。所导出的理论不仅对细观颗粒力学领域，而且对剪切问题的有限元分析领域都具有极大的价值。

***9813299ChangPrevious studies have shown that the usual concept of strain (firstgradient of displacement) cannot adequately describe the near- andpost-failure behavior of granular material under large deviatoric loadingcondition. In this research, the concept of using additional kinematicdescriptors other than the usual concept of strain will be explored. Theoverall objective of the work is to develop micro-granular mechanicaltheories using new kinematic descriptors so that the theories areapplicable to the entire range of stress-deformation behavior.The approach employed will be based on a micro-macro approach in which thebehavior of an assembly is linked to the properties of particles.Experimental data and computer simulation will form an integral part in thedevelopment of the theory. The developed micro-granular mechanical theorywill be implemented to a finite element environment. The model will bevalidated by comparing measured and predicted behavior of granularmaterials under different loading conditions.The result of this research will provide insight into the theoreticalframework of material localization and bifurcation in continuum mechanics.The intrinsic length of material, which plays a major role in localizedfailure zones, will be directly related to the micro-structure. Thisunique feature significantly distinguishes this theory fromphenomenologically based models. The derived theories are expected to beextremely valuable not only to the field of micro-granular mechanics butalso to the field of finite element methods in the analysis of shearproblems.***