题目：Bridging the Micro-Macro Response of Granular Materials: 3D Experiments and Non-local Numerics.
报告人：Dr. Joshua Albert Dijksman
单位：荷兰瓦格宁根大学 (Wageningen University & Research Center, Netherlands)
摘要：If you walk on sand, it supports your weight. How do the disordered forces between particles in sand organize, to keep you from sinking? This simple question is surprisingly difficult to answer. Experimentally, it is challenging to measure microscopic forces between deeply buried grains in three dimensions. In my talk, I will describe experiments in which we have succeeded in measuring forces inside a granular packing subject to controlled deformations. I will detail how one can connect the measured micro-scale forces to the macro-scale packing force response with an averaging, mean field calculation. This calculation explains how the combination of packing structure and contact deformations produce the unexpected non-linear mechanical response of the packing, and reveals a surprising microscopic particle deformation enhancement mechanism. Numerically, the non-linear packing response is also difficult to reproduce with standard methods; I will also briefly discuss our new discrete element method for dense granular packings that in fact can reproduce many of the observed microscopic and macroscopic observations from our experiments.