Finite element predictions of residual stresses in cold-formed steel sections

Residual stresses in cold-formed sections may play a significant role in determining their behaviour and strength.Laboratory measurements of residual stresses by destructive methods are not only time-consuming but also of limited accuracy.This paper describes a finite element-based method for predicting residual stresses in press-braked thin-walled sections,which overcomes these difficulties.The method offers a powerful tool for exploring the effect of different forming parameters on the magnitude and distribution of residual stresses,so that these forming parameters can be optimized.In this method,the effects of coiling and uncoiling are accounted for analytically,with the resulting residual stresses specified as initial stresses in a subsequent finite element simulation of cold bending.Numerical results from this method are shown to agree closely with laboratory measurements,demonstrating the validity and accuracy of the method.The present method provides residual stress distributions over the cross-section as well as across the thickness,and also explains why residual stresses may differ considerably in otherwise identical sections.