In this work, Discrete Elements Method simulations are carried out to investigate the effective stiffness of an assembly of frictional, elastic spheres under anisotropic loading. Strain probes, following both forward and backward paths, are performed at several anisotropic levels and the corresponding stress is measured. For very small strain perturbations, we retrieve the linear elastic regime where the same response is measured when incremental loading and unloading are applied. Differently, for a greater magnitude of the incremental strain a different stress is measured, depending on the direction of the perturbation. In the case of unloading probes, the behavior stays elastic until non-linearity is reached.Under forward perturbations, the aggregate shows an intermediate inelastic stiffness, in which the main contribution comes from the normal contact forces. That is, when forward incremental probes are applied the behavior of anisotropic aggregates is an incremental frictionless behavior. In this regime we show that contacts roll or slide so the incremental tangential contact forces are zero.

Graphical Abstract

中文翻译：

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各向异性粒状材料的DEM模拟：弹性和非弹性行为

在这项工作中，进行了离散元素方法仿真，以研究各向异性载荷下摩擦弹性球体组件的有效刚度。在多个各向异性水平上执行沿着前向路径和后向路径的应变探针，并测量相应的应力。对于很小的应变扰动，我们获取线性弹性状态，其中在施加增量加载和卸载时测量的响应相同。不同地，对于更大的增量应变，根据扰动的方向测量不同的应力。在卸载探针的情况下，行为保持弹性直到达到非线性为止。在前向扰动下，聚集体显示出中间的非弹性刚度，其中主要贡献来自法向接触力。即，当应用前向增量探针时，各向异性聚集体的行为是增量无摩擦行为。在这种情况下，我们表明接触滚动或滑动，因此切向接触力增量为零。

图形概要