Effect of Strain Rate and Plastic Pre-strain on the Ductility of Structural Steels.

Ductile fracture processes in structural steels under high strain rates have been investigated by tensile test. Under high strain rate loading, the ductility of the steels decreases. The reasons for this decrease is discussed from the analysis of ductile fracture process, as especially of void nucleation strain and void growth strain up to fracture. A three-dimensional void coalescence model for the high strain rate loading was obtained by modifying Thomason's static three-dimensional void coalescence model. The model was used to predict the void growth strain and evaluate the effect of strain rate on void coalescence. The influence of plastic pre-strain on ductility under high strain rate loading was also investigated.