Investigation on transient electrically-assisted stress relaxation of QP980 advanced high strength steel

• The paper employs the electric pulses to promote the relaxation of residual stress.
• At 373 K, the residual stress decreases with increasing electric parameters, and the athermal effect of the electric pulses is observed.
• A model of electrically-assisted stress relaxation and a springback angle prediction model considering electric pulses are proposed and verified.

Advanced high strength steels have been increasingly used in auto body manufacturing industry to reduce weight and increase safety. However springback often occurs after stamping and seriously affects the forming accuracy, which is one of the bottle necks of its application. Targeting to control the springback, a novel method which employs the electric pulses to promote the relaxation of residual stress is investigated. In order to achieve this goal, electrically-assisted stress relaxation tests were carried out which shows that at a relative lower temperature, 373 K, the residual stress decreases with increasing electric parameters, and the athermal effect of the electric pulses is observed. A model of electrically-assisted stress relaxation is proposed. By combining the proposed stress relaxation model and the perfect plastic material model, a springback angle prediction model considering electric pulses is also proposed. The proposed models are verified with experimental results.