Shape optimisation of parts in dynamic mechanical systems with respect to fatigue

Abstract

Computer aided engineering has gained increasing significance in product development processes and research in recent years. Simulation techniques and CAE methods are becoming more and more significant as strategic success factors. While the finite element method and multibody system simulation are state-of-the-art in many fields of application, structural optimisation methods are not so widely used. Although much progress in development has been achieved in recent years, their successful application is often still time-consuming and sometimes not even possible. Further research work and development is necessary to improve both the capabilities of structural optimisation methods and their usability. The research work presented in this paper is a contribution towards producing an integrated structural optimisation process, introducing a new shape optimisation approach. The new process allows an integrated investigation of dynamically loaded parts in complex mechanical systems and a straightforward optimisation with respect to fatigue. Coupling effects between optimisation operations and system dynamics are fully covered. Finite element analysis (FEA), multibody system simulation (MBS), fatigue analysis and shape optimisation are tied together into a fully automated process. The whole optimisation loop, which is an iterative procedure, incorporates all these analysis steps and is implemented in a straightforward, batch-oriented manner using well-known standard software. Since the whole process involves several different analysis types, the resulting setup is rather complex and the reader may not be familiar with all the terms arising within the context. Therefore, some essential aspects of each of the stages involved in the process are explained, to provide the reader with important concepts. An academic example is discussed in depth, to illustrate and clearly outline the potential of this method. The results clearly show the importance of covering fatigue aspects in shape optimisation problems of parts in dynamic systems. In particular, the interaction between the dynamic properties of the part and the overall system, as well as its implications on the optimisation process are demonstrated. Finally, a more complex application, namely the optimisation of a passenger car suspension arm, is presented. This example demonstrates the applicability and feasibility of the optimisation process for real world problems.

Keywords:

• Shape optimisation
• Fatigue analysis
• Multibody systems