Simulations of Assembly/Disassembly (A/D) processes covers a large range of objectives, i.e. A/D sequencing, path finding, ergonomic analysis. This paper deals with a simulation framework for A/D analysis based on a new simulation preparation process allowing to address up to two types of shape representations (B-Rep NURBS and polyhedral), thus handling efficiently the configurations where 3D shape representations of assemblies play a key role. The simulation preparation process is illustrated by some specific steps allowing the automatic identification of the contacts for a 3D product model. Their corresponding list is after then described. During the identification process, three major stages of the framework are detailed: model tessellation, surface merging and contacts identification.