A comparison in terms of accuracy and efficiency between a MBS dynamic formulation with stress analysis and a non-linear FEA code

To perform the mechanical design of a machine through computer-aided techni ques, at least three main different products should be used: a CAD software , to model the parts of the machine; a MBS program, to analyse the kinemati cs and dynamics of the whole system; and a FEA code, to determine the level of stress and strain suffered by each component. If it is true that CAD so ftware is usually well connected with the two other tools, the same does no t happen in what respects to FEA-MBS interfaces. Moreover, since both the l arge-amplitude motion and the elastic deformation are coupled, they cannot be solved separately, and the usual practice consisting of first analysing the machine motion assuming rigid bodies, and then calculating stresses und er the loads previously generated, is just an approximation. In order to pr ovide mechanical designers with a tool which makes easier and shorter the d esign-cycle, this paper presents a comparison between the two options that are currently available to address the mentioned problem: a dynamic MBS for mulation which simultaneously solves motion and performs stress analysis by considering flexible bodies; and a non-linear module of a FEA code, which takes into account large displacements and finite rotations. The comparison is carried out in terms of accuracy and efficiency through four examples. The results lead to the conclusion that, for similar accuracy, the first me thod is largely more efficient. Therefore, the interest of developing MBS c ommercial codes which integrate motion calculation and stress analysis thro ugh the mentioned approach is envisioned, as long as they would provide fas ter solutions. Copyright (C) 2001 John Wiley & Sons, Ltd.