The finite cell method for the prediction of machining distortion caused by initial residual stresses in milling

Abstract

Machining distortion caused by residual stresses is one of the major challenges in the production of thin-walled monolithic parts, which are widely used in the aerospace industry. This distortion often results in large deviations in form and position outside the tolerance requirements of the part. Time-consuming and cost-intensive running-in processes or manual reworking are therefore necessary to meet the tolerances of the parts. Current research mainly uses the finite element method (FEM) to predict machining distortion caused by residual stresses. However, the disadvantage of the FEM is the high manual effort required to generate a computational mesh of the in-process workpiece (IPW). Moreover, the FEM demands a very fine mesh, which has to be frequently updated by remeshing, to be in good agreement with the IPW. This leads to high computation times overall. In this paper, a novel machining distortion prediction method based on the Finite Cell Method (FCM) is presented. A major advantage of FCM compared to the established FEM in the context of milling simulation is the decoupling of the computational mesh and the IPW geometry, which allows for analysis updates of the modified IPW due to material removal, without the need for expensive re-meshing. Thus, the time complexity of the simulation can be reduced significantly. The milling process of a thin-walled part made of Ti-6Al-4V was considered to demonstrate the overall simulation approach.