Influence of Surface Groove Morphology on Formability Prediction of Q-P-T Steel

In order to determine the reasonable groove angle and groove depth ratio in groove models of forming limit diagram (FLD) theory, the novel quenching-partitioning-tempering (Q-P-T) steel was investigated. Some tensile samples with different groove angles (45°, 60°, 90°) and groove depth ratios (5%, 10%, 15%, 25%) were prepared, and their uniaxial tests were also performed. After that, different constitutive models were used to fit the tensile curves, and the strain limit values under uniaxial tension were calculated by using Swift-Hill equation and compared to the empirical data. The results indicate that the most suitable situation for predicting FLD was determined at the groove depth ratio being 5% and the groove angle being equal to or smaller than 45°. The calculation method of strain limit values under uniaxial tension is the base of those of strain limit values under other loading modes composing whole FLD.