On the interplay of friction and stress relaxation to improve stretch-flangeability of dual phase (DP600) steel
Dilip K. Banerjee, Kali Prasad, Krishnaswamy Hariharan, Uday Chakkingal
Industrial servo press has successfully demonstrated improved formability when deforming sheet metals. While the time dependent viscous behaviour of material is attributed to the observed formability improvement, much less efforts have been devoted to understand and quantify the underlying mechanisms. In this context, hole expansion test (HET) of a dual phase steel was interrupted at pre-defined punch travel heights to understand the time-dependent effects on stretch-flangeability. The effect of pre-strain, hold time and edge quality on HER improvement was studied. The present study shows that the hole expansion ratio (HER) improves significantly in interrupted HET. This improved HER is due to the combined effects of stress relaxation and friction on deformation behavior. The ductility improvement estimated from uniaxial stress relaxation tests was used to estimate the contribution of stress relaxation and friction respectively in HET. This study shows that friction plays a significant role in improving HER at high pre-strain. It was also demonstrated that frictional effects are largely influenced by edge quality.
CIRP Journal of Manufacturing Science and Technology
, Prasad, K.
, Hariharan, K.
and Chakkingal, U.
On the interplay of friction and stress relaxation to improve stretch-flangeability of dual phase (DP600) steel, CIRP Journal of Manufacturing Science and Technology, [online], https://doi.org/10.1016/j.cirpj.2020.11.014
(Accessed April 22, 2021)