Simulation of springback variation in the U-bending of tailor rolled blanks

Abstract

The springback behaviors of tailor rolled blanks with high-strength steels including CR340, DP590 and Q&P980 together with light aluminum after U-channel forming are investigated. Besides the material selection, the springback characteristics of equal thickness blanks and tailor rolled blanks are compared and analyzed by experimental and simulation methods. The comprehensive springback angles in thin and thick sides of TRBs reach 90.4° and 91.05° for the aluminum, 91.06° and 90.83° for CR340, 90.53° and 90.32° for DP590, 105.08° and 98.49° for Q&P980, respectively. Due to different flexural modulus, the stress is more likely to concentrate in the thin zone, and the stress gap between thin and thick side is rising from 15 to 290 MPa with the material strength increasing. The thickness thinning in thin zone is more noticeable, and the maximum thinning is particular in the straight wall of forming tools. Moreover, the released longitudinal stress is adopted to investigate the degree of springback. It is obvious that more elastic longitudinal stress is released by the material with higher strength, and the changes of longitudinal stress in the transition zone of tailor rolled blanks show the gradient distribution accompanied by thickness variation.