Fatigue Life Simulation for Optimized Exhaust Manifold Geometry 2006-01-1249

Modern exhaust systems must withstand severe cyclic mechanical and thermal loads throughout the whole life cycle. Growing demands on designs targeted at reliability and cost optimization require new methods in lifetime prediction.

Presently, highly loaded parts like exhaust manifolds are predominantly designed experimentally by means of lengthy and expensive component tests. Further shortening of development time without quality loss is possible only by increasing the application of computer simulation.

A procedure is presented supporting the component development as soon as it is in an early design stage, its main aim being a reduction of component tests. The numerical model is capable of handling complex thermo-mechanical loading histories by a visco-plastic constitutive model. The local damage processes are modeled based on the growth of micro-cracks, including relaxation and hold-time effects. Said tool is currently evaluated by ArvinMeritor on customer projects with respect to its predictive capabilities. Its utilization will help speed up the development process and also increase further product quality. The comparison of component test results with predictive simulations shows that the test results are comparable with the predictions. This new methodology will be a significant step to virtual development. The present paper will combine the theoretical background with the practical evaluation on real designs.