Most parts of auto-body are produced through the sheet metal forming process, and during this process they have change of thickness and residual stress and strain remain. In this paper, to specify dynamic material properties considering this pre-strain effect, materials SPCEN, SPRC45E and SPRC35R were selected and were imposed 5, 10% pre-strains. After that using the high speed material testing machine, materials were tested at given strain rates of between 0.003 and 50 s-1. It was found from experimental results that in case of SPCEN and SPRC35R, the yield stress and ultimate stress were increased due to pre-strain effect at strain of over 10 s-1 but SPRC45E was not affected by pre-strain effect.
Pre-strain effect; Strainrates; High speed material testing machine