Improving Crash Analysis Through the Estimation of Residual Strains Brought About by Forming Metal

This paper describes a method that can be used to estimate the residual strains from the forming of sheet metal without running forming simulations. For a first-order crash analysis, using estimated residual strains rather than the strains reported from several forming simulations increases the speed of the design process. The method estimates residual forming strains from the part geometry itself and assumes that the part was formed from a planar sheet of metal. The importance of considering the forming history of a part is demonstrated by comparing crash analysis results with and without the consideration of these residual strains. Along with this, physical test results will be compared of a part as formed and an identical part which was heat treated to relieve some of the cold working strains. Once the importance of considering forming history has been established, an alternative method of estimating residual strains will be examined. Crash analysis results using forming simulation residual stresses and strains will be compared to analysis results using estimated strains from the alternative method. Finally the scope of application of this strain estimation method will be discussed.