Influence of strain rate on ductile versus brittle fracture for ductile cast iron EN-GJS-500-14 in V-notch three-point bending tests

Abstract

Three point bending tests on V-notched specimens machined from a component cast in EN-GJS 500-14 nodular iron solid solution strengthened by silicon have been carried out. The 3P bending tests were performed at different stroke speeds (10-3 ~ 102 mm/s). The resulting strain rates at the V notch varied in the range of 1·10-4 ~ 5,8 s-1. The fracture surface of 3P bending tests was quantified in terms of ductile and brittle fracture using Scanning Electron Microscope (SEM). EN-GJS 500-14 has an increased brittle behavior with increasing strain rate. Predominately ductile fracture was observed for the strain rates 1·10-4~4·10-2S-1. . At the strain rate of about 1 s-1 more significant change in ductile to brittle fracture is seen. The 3P bending tests at -15°C showed predominately brittle fracture for the strain rates investigated 3,6·10-2 ~ 2,3 s-1.