In this work the dynamic fracture toughnesses, $J_1d$ and $CTOD_1d$ were determined by multi-specimen method for SCM4 which behaviors ductile fracture in room temperature.
The experimental results showed that the variation of $J_1d$ and $CTOD_1d$ with respect to initial crack ratio and impact velocity was small. Also, it is found that the dynamic fracture toughnesses, $J_1d$ and $CTOD_1d$ are larger than the static fracture toughnesses, $J_{1c}$ and $CTOD_{1c}$, respectively. This shows similar result Rolfe insists that the absorbed energy in impact CVN tests is larger than the one in slow bend CVN tests at the upper shelf region.
