Abstract
In digital mock-up (DMU), the realistic modelling of assemblies with geometrical and dimensional defects is among the main goals of several research works. This modelling allows the prediction of the mechanical and functional behaviour of mechanisms at the early stages of the product life cycle. However, the assumption of rigid body is adopted in most of the CAD tools and several physical factors such as the deformations due to mechanical and thermal loads are neglected. Then, the integration and the interaction between mechanical design tools as well as engineering calculation and analysis tools are required. In this regard, this paper proposes an interactive CAD model for the tolerance analysis of mechanical assemblies by considering both manufacturing defects and thermo-mechanical deformations of parts. The dimensional and geometrical tolerances are taken into account by determination of the assembly configurations with defects based on the worst case approach and the small displacements torsor parameters. A finite element model is applied to simulate the deformations of non- rigid parts resulting from thermo-mechanical loads. A novel method based on the use of the Levenberg Marquart algorithm is applied in this work to reconstruct the B-spline surfaces corresponding to deformed faces of non-rigid parts. The final CAD model of realistic components is obtained from the above reconstructed surfaces. The mating constraints between couples of rigid and non-rigid parts are updated at the end to obtain all the realistic configurations of the assembly and to control the functional requirement. The industrial case study shows that the presented tolerancing model is an interactive decision support tool for engineers and designers in DMU.