Rate-dependent 1D Compression in Crushable Granular Media

Abstract

The behaviour of granular substances in relation to strain rate, particularly under quasi-static load conditions, varies and is not uniformly definable. This ambiguity is attributed to several contributing factors, such as the form, size, and susceptibility to fragmentation of the particles. This rate-dependent response of granular substances is crucial in many sectors where both particle fragmentation and the rate of loading are involved. The objective of this study is to computationally examine these rate effects at the grain scale, and to correlate these findings with the macroscopic response during the fragmentation process. Numerical simulations of one-dimensional (1D) compression imply that quasi-static loading, which typically results in a rate-independent reaction, could result in rate-dependent characteristics during particle fragmentation. The stress response and the fragmentation events are controlled by the changes in the distribution of contact forces within the granular structure at different loading velocities. A slower strain rate compression tends to result in a uniform distribution of contact forces between the particles, which subsequently reduces the strength through particle reorientation and reorganisation. In contrast, a faster strain rate encourages localized fragmentation within a smaller set of particles, leading to observable strain hardening.