抄録
Charpy-V notched specimens were prepared and the strain rate dependency of bending transition properties of ductile cast irons were investigated. Impact bending tests at loading velocities up to 10m/s (nominal strain rate for the specimens up to 103/s) were performed with hydraulic impact loading machine. The experimental results demonstrate that the ductile-brittle transition curve rises to higher temperature side with the increase in the strain rate. This transition curve rises higher in the as cast material with higher pearlite content in the matrix, than those of ferritic material. The bending yield stress and the maximum stress were found to increase with increasing strain rate and deceasing temperature. The transition temperature and the behavior can not be simply estimated by strain rate-temperature parameter, R-value. Sstrain rate dependency on the brittle fracture behavior exists, and it seems to relate with the crack arrester effect of graphite nodule against brittle crack propagation.
