A numerical study on chain-die forming of the AHSS U-channel and contrast with roll forming

Abstract

Advanced high strength steels (AHSS) pose great challenges to sheet metal forming processes in vehicle components manufacturing with their increasing high strength and surface hardness. Chain-die forming is a recently proposed manufacturing method alternative to roll forming, aiming at reducing the redundant strain by enlarging the deformation length through a remarkably large rotation radius. In this work, the performance of AHSS in chain-die forming is investigated by experiment and simulation. The mechanical tests and chain-die forming tests on four AHSS materials are performed. The Chaboche hardening model to describe the Bauschinger effect of the AHSS is established and implemented into the finite element model of chain-die forming process. The evolution of longitudinal strain and springback are elaborated and discussed. Furthermore, a systematic comparison between chain-die forming and roll forming of the U-channel are performed based on the verified FE model. The chain-die forming has obviously smaller and less fluctuate longitudinal strain on the flange, mainly because chain-die forming has a smoother transitional surface. Chain-die forming can alleviate web bow; the flange width of the chain-die formed U-channel presents a monotonic increase trend along the longitudinal direction, while the flange width of the roll-formed shows a fluctuate trend. On the other hand, the springback after chain-die forming is larger than that after roll forming, which implies more compensation is needed to obtain a desired product.