Prediction of residual stress on cold-formed curvature plates by elastoplastic material model

To meet the demand of automatic production, the multisquare punch forming has been improved to process complex curved plates. However, the improved forming equipment improves the processing quality to the maximum extent, and springback and residual stresses are inevitable phenomena in the cold bending process. Residual stress is an important factor that causes fatigue crack and stress corrosion crack. And the residual stress in machining will seriously affect the fatigue life of cold-pressed parts. Therefore, it is necessary to quantitatively and qualitatively analyze the residual stress caused by the cold forming equipment. Through theoretical derivation and finite element simulation methods, the residual stress distribution for thick plates in the cold forming process was analyzed and compared in this article. Meanwhile, the variation law of residual stress peak with thickness and forming radius was further discussed. The results show that the residual stress distributions obtained by the two theoretical models are in good agreement with the numerical results. The maximum error of peak residual stress is about 10%, which verifies the reliability of theoretical formulas.