1983 Volume 32 Issue 355 Pages 366-371
The elastic-plastic fracture toughness JIc tests by the stretched zone method were performed to obtain JIc values for machine structural steels. The validity of the JIc values obtained was evaluated, and the effects of the heat treatment conditions and microstructure of steels on the JIc values were investigated by use of streched zone width, SZW.
The results obtained are summarized as follows.
(1) The inclination of the blunting line in SZW versus J curve is hardly affected by the condition of heat treatment for SCM440 steels, while it is affected obviously for S45C steels.
(2) The relation between SZWC and σB varies with the difference of microstructure and with the ratio of ferrite area to pearlite area in ferrite-pearlite steels.
(3) SZWC versus JIc/σfs diagram (in log. scale) can be arranged by two linear lines according to the difference of microstructure.