Yield strength tracking of UOE pipe considering various thickness-to-diameter ratios

Abstract

Abundant literature was dedicated to the numerical tracking of the yield strength of cold formed pipes throughout their forming process. However, the flattening process conducted on straps sampled from the formed pipe for tensile test as well as the residual stress developed after each stage were not considered in most studies. Therefore, a simulation-based finite element analysis program was developed to replicate the UOE forming of steel pipes and track the yield strength throughout the forming process and final flattening considering the residual stress. The accuracy of the simulation was validated through comparison with experimental data for API 5L X70 steel pipe. In this study, the program is employed to examine the causes leading to the change in the yield strength at each forming stage. In addition, the effect of the thickness-to-diameter ratio (t/D) on the yield strength is evaluated. The consideration of the residual stress in the simulation enabled to find the existence of a critical range for t/D beyond which further improvement of the yield strength cannot be achieved.