Abstract: The impact response of Charpy pre-cracked specimen under dynamic loading was analysed by use of elastic-plastic dynamic finite element method. Analysis results showed that the effects of inertia force on J-integral around crack tip can be ignored in the loading rate range of general impact test machine. In practice, therefore, so long as appropriate mathematic treatment was used to carry out the load-time curve, dynamic J-integral can calculated according to the J-integral formula for quasistatic loading. In addition, the experiments proved that the crack onset point of Charpy pre-cracked specimen can be satisfactorily detected by using strain gage pasted on the crack tip under impact loading.

Key words: Crack tip, Finite element method, Impact response