Yield Stress and Flow Stress of Iron and Steel under Dynamic Loading

The dynamic tensile tests of pure iron and low carbon steel at a strain rate of 30/sec were performed at room temperature and −78°C. The results of measurements of the yield and the flow stress were analyzed on the basis of the Petch equation and discussed with emphasis on the effects of the impurity amount and of the amount of prestrain on the strain rate and the temperature dependence of frictional stress. It was found that the strain rate and temperature dependence of frictional stress was neither influenced by the presence of interstitial elements nor affected by the amount of prestrain. Therefore it was concluded that the strongly thermally activated motion of the dislocations is the process of surmounting the lattice intrinsic potential barrier such as the Peierls potential, which was confirmed by the small value of the activation volume.