FEM-DEM Dialogue for Tribological Understanding
In many mechanisms, global dynamics resulting from operating conditions act as external solicitations for bodies in contact. As a consequence, dynamic instabilities occur in the contact and lead to particle detachments, usually called 3rd body and wear flow. Obviously, once detached, these particles play an important role in the evolution of the local friction coefficient and thus the local contact dynamics. As the contact is a confined area, experimental investigations have mostly been unsuccessful to locally describe both contact dynamics and material flows. To balance this lack, two numerical methods can be used to solve independently each part of the problem. From a global point of view, local contact dynamics is considered as a local condition for the two 1st bodies described as continuous media. From a local point of view, the discontinuity of the interface should be taken into account to describe material flows, considering effect of two bodies as boundary conditions. To model continuous aspects, a semi-implicit dynamic Finite Element (FE) method is used taking into account the elasto-plastic behaviour of the two bodies in contact. To model discontinuous effects, a non conventional Discrete Element (DE) method is used, called the Non Smooth Contact Dynamic (NSCD) method coupled with Cohesive Zone Models (CZM) to describe the behaviour of the 3rd body particles. To give a reliable description of the behaviour of bodies in contact, a coupling of scales is required on both local conditions and boundary conditions which are respectively inputs coming from DE and FE methods. The aim of the present paper is to gather these two complementary approaches by creating a numerical dialogue between DE and FE methods acting respectively at the 3rd and 1st bodies scales. After a brief description of each numerical model, the dialogue methodology will be detailed and applied to a reference example where dynamic instabilities occur in the contact. A comparison between results obtained with “classical” FE simulation and “coupled” FE-DE simulations is presented. As a conclusion, this numerical dialogue is a first step toward a better taking into account of the 3rd body behaviour in continuum model and its consequences on local contact dynamics.