Product/Process Tolerancing Modelling and Simulation of Flexible Assemblies - Application to a Screwed Assembly with Location Tolerances

In industry, the modelling of product/process assemblies is based on the theory of Geometrical Product Specification – GPS – and Tolerancing Analysis. This industrial approach follows several international standards to specify the parts and build stack-ups models of tolerances of an assembly. The main hypothesis of these standards is the rigid workpiece principle. However, for large dimensions thin parts and assemblies as example, the effects of gravity and of the forces and/or displacements imposed by active tools, this rigid bodies assumption is not acceptable and “classic rigid stack-ups” can lead to non-representative results on functional requirements. Thus, this paper proposes an approach to take into account the flexibility of the parts and assemblies in the 3D tolerancing stack-ups. Coupling the tolerancing theory, the structural reliability approaches and FEM simulation, an original approach based on the stochastic polynomial chaos development method, the Sobol’s indices and FEM method is developed to build 3D flexible stack-ups and to estimate the main tolerance results. The choice of chaos meta-model is done to be close enough philosophy and form of the linear model of the standard NF E04-008:2013.