Dynamic Constitutive Equations of Auto-body Steel Sheets with the Variation of Temperature (I)-Dynamic Material Characteristics with the Variation of Temperature

Abstract

This paper is concerned with the thermo-mechanical behavior of steel sheet for an auto-body including temperature dependent strain rate sensitivity. In order to identify the temperature-dependent strain rate sensitivity of SPRC35R, SPRC45E and TRIP60, uniaxial tensile tests are performed with the variation of the strain rates from 0.001/sec to 200/sec and the variation of environmental temperatures from – 40℃ to 200℃. The thermo-mechanical response at the quasi-static state is obtained from the static tensile test and that at the intermediate strain rate is obtained from the high speed tensile test. Experimental results show that the variation of the flow stress and fracture elongation becomes sensitive to the temperature as the strain rate increases. It is observed that the dynamic strain aging occurs with TRIP60 at the temperature above 150℃. Results also indicate that the flow stress and fracture elongation of SPRC35R are more dependent on the changes of strain rates and temperature than those of SPRC45E and TRIP60.