Tensile flow behavior of ultra low carbon, low carbon and micro alloyed steel sheets for auto application under low to intermediate strain rate

• Tensile characteristics of auto grade steel sheets under low to intermediate strain rates.
• Yield stress increment is higher for low and ultra low carbon steels in intermediate strain rates.
• Strain hardening rate drastically decreases with strain rate for low and ultralow carbon steels.
• A constitutive model to predict the strain rate sensitive flow behavior of all these steel grades.

This paper is concerned with tensile characteristics of auto grade low carbon, ultra low carbon and micro alloyed steel sheets under low to intermediate strain rates ranging from 0.0007 to 250 s−1. Experimental investigation reveals two important aspects of these steels under intermediate strain rate deformation. Firstly, the yield stress increases with strain rate in all these steels. Of course yield stress increment is higher for low carbon and ultra low carbon steel sheets. Secondly, the strain hardening rate drastically decreases with strain rate for low carbon and ultra low carbon steel sheets, whereas it remains steady for micro alloyed steel sheets. Based on these observations, a constitutive model has been proposed which predicts the strain rate sensitive flow behavior of all these grades within the strain rate range of automotive crash event.