Experimental and finite element robustness studies of a bumper system subjected to an offset impact loading

Abstract

A product of high quality is a product that performs well, not only in exactly the situations it was designed to handle but also in slightly different situations that arise in the usage of the product. As a specific example, the performance of a bumper system should not depend on small fluctuations in the manufacturing process or on small variations in the impact event. In this work, the robustness of an existing vehicle bumper system subjected to a crash load has been evaluated both experimentally and numerically. In the latter case, different widely used approaches to numerically assess the robustness have been utilised. A reliable numerical robustness study provides the designer with a valuable tool for improving a design, and an evaluation of these methods in this context is therefore of interest. It is concluded that for the example under study, both the Monte Carlo method and the metamodel-based Monte Carlo methods work well. Furthermore, for moderate dispersions levels, i.e. a small design space with no bifurcation in the deformation pattern, a linear response approximation is shown to have a sufficient accuracy to be used in the metamodel-based robustness analysis. The performed numerical robustness studies also point out that the performance of a nominal simulation, i.e. a simulation conducted with mean values for all variables, does not in general predict the mean performance of the finite element model. Finally, some possible design improvements for the bumper system under study are also identified.

Keywords:

• experimental robustness
• numerical robustness
• Monte Carlo
• metamodel
• sensitivity analysis

Acknowledgements

This work has been carried out with financial support from the ROBDES project, funded by the Research Council of Norway, Hydro Aluminium Structures, Volvo Car Corporation, Scania, SSAB Tunnplå t and Gestamp Hardtech. Special thanks for Volvo Car Corporation for providing the bumper systems and Gestamp Hardtech for allocating test resources. We would also like to thank Robert Westerlund for his work with the experiments.