An alterable constitutive law of high-accuracy DEM model of lunar soil

Abstract

The accuracy of discrete element model has great influence on the DEM simulations of lunar soil, especially on the soil-tool interaction simulations. In this paper, the mechanical property of lunar soil is classified into three categories and the particularity of shear strength is newly explained as higher internal friction angle and lower cohesion with respect to Earth soil, and the plasticity performance of lunar soil is emphasized. Two different constitutive laws are established as non-cohesion and apparent-cohesion ones, mainly distinguished by spring tension. Then four common kinds of addition methods of tension are introduced and compared in terms of limiting particles’ motion. The reason why spring tension is the most suitable tension model to simulate the cementing bond is analyzed from the perspective of soil aggregation theory and lunar soil chemical composition. An initial bonding state assumption is proposed, based on which a new alterable constitutive law is established to obtain a high-accuracy DEM model of lunar soil. Finally, the accuracy is verified by both shear strength indices and elastic-plastic behavior under both loose and dense conditions.