ABSTRACT
A discrete element analysis is a dynamic or transient analysis that considers the dynamic interaction of a system of interacting particles. A particulate DEM model creates an ideal system of rigid particles that can move, connected by rigid springs that simulate the contact interactions. (The contact spring formulations are outlined in Chapter 3). As particles move away from each other contacts are broken and some of the springs will be removed; at the same time additional springs will be introduced as new contacts are formed. The continuous removal and introduction of contact springs results in a change in the overall system stiness. A reduction in stiness will also occur if a contact starts to slide. Therefore the analysis is non-linear. This non-linearity could be described as a geometrical non-linearity as it arises owing to a change in the local packing geometry of the particles. As will be discussed in Chapter 3, the contact constitutive model used to describe the force displacement response at the contacts is often non-linear, and this adds a material non-linearity to the system. These two particle-scale sources of non-linearity combine to give an overall non-linear macro-scale material response. At larger strains where sliding occurs the geometric non-linearity caused by gross movements at the contacts and \buckling" mechanisms that can develop in local groups of particles will dominate the response,
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while the in uence of the non-linear response at the contacts will be more evident at small strain levels, before the onset of sliding.
