DEM crack propagation using a FEM-DEM bridging coupling

Abstract

<p><span dir="ltr" role="presentation">The behavior of seismic faults depends on the response of the discrete microconstituents trapped in </span><span dir="ltr" role="presentation">the region between continuum masses, which is usually termed “gouge”. The gouge is a particle region </span><span dir="ltr" role="presentation">composed of amorphous grains. Conversely, the regions surrounding the gouge can be conceptualized </span><span dir="ltr" role="presentation">as continua. The study of such system dynamics (slip) requires the understanding of several scales, </span><span dir="ltr" role="presentation">from particle size to meter scale and above, to properly account for loading conditions.</span> <span dir="ltr" role="presentation">Our final </span><span dir="ltr" role="presentation">objective in this study is to assess to what extent we can understand friction by leveraging an analogy </span><span dir="ltr" role="presentation">to fracture. Dynamic friction between sliding surfaces resembles a dynamic mode-II crack, but this </span><span dir="ltr" role="presentation">equivalence is brought into question when granularity at the interface is considered. Based on the </span><span dir="ltr" role="presentation">theory of linear-elastic fracture mechanics (LEFM), a stress concentration should be observed at the </span><span dir="ltr" role="presentation">rupture front if indeed friction can be modeled with the toolkit of LEFM.</span></p> <p><span dir="ltr" role="presentation">Simulating this system numerically remains a challenge, as, in order to capture proper physics, both </span><span dir="ltr" role="presentation">the continuum and discrete aspects of the system must be harmoniously incorporated and coupled into </span><span dir="ltr" role="presentation">a single model. An energy-based coupling strategy between the Finite Element Method (FEM), used </span><span dir="ltr" role="presentation">to resolve the continuum portions, and the Discrete Element Method (DEM), to model the granularity </span><span dir="ltr" role="presentation">of the interface, is used [2]. In this exploratory study, we begin by modeling a medium with strong </span><span dir="ltr" role="presentation">inter-granular cohesion [1]. <span id="divtagdefaultwrapper" dir="ltr">The use of the coupling ensures a large enough effective domain to control nicely the crack propagation.  The linear-elastic properties of both DEM and FEM portions are therefore matched to avoid wave reflections. </span></span><span dir="ltr" role="presentation"> Both mode-I and mode-II cracks are considered.</span></p>