Effect of strain rate on fracture toughness of mild steel

The effect of strain rate on the yield strength and fracture toughness of m ild steel was studied in the strain rate range 10(-5)-10(-2) s(-1). The low er yield strength was found to be independent of strain rate in the range 1 0(-5)-10(-3) s Beyond this strain rate, the lower yield strength was found to vary linearly with logarithm of strain rate up to a value of 10(2) s(1). Fracture toughness was also found to increase with strain rate up to a val ue of 10(-3) s(-1) and subsequently decrease gradually with increasing stra in rate, However, a drastic reduction in fracture toughness was observed at a strain rate of 10(2) s(-1). This reduction was attributed to the change in fracture mode from ductile to cleavage. (C) 2001 IoM Communications Ltd.