Experimental & numerical study of sidewall curl in advanced high strength steels
Sidewall curl is a type of springback deformation resulting from successive bending-unbending when a sheet metal is drawn over a die radius or through a drawbead. In this study, the sidewall curl in stamped AHSS parts (TRIP780 and DP980) was predicted using four models from LS-DYNA material library: 24, 36, 37, 125 and a UMAT in ABAQUS based on the Yoshida-Uemori model. Various material characterization tests were analyzed to identify the input parameters. Plane-strain channel sections were drawn in a specialized die with adjustable drawbeads and various die entry radii and compared with simulation results. By increasing drawbead penetration, the springback angle decreased but the sidewall curl increased in the channel sections. For simulations in LS-DYNA, MAT37 with increased integration points predicted the most accurate results. The YU model in ABAQUS showed less than 8% error compared to the predicted sidewall curl for channel sections with shallow drawbeads.