Evaluation of dynamic fracture toughness KId by Hopkinson pressure bar loaded instrumented Charpy impact test

A novel method for measuring the dynamic fracture toughness, KId, using a Hopkinson pressure bar loaded instrumented Charpy impact test is presented in this paper. The stress intensity factor dynamic response curve (KI(t)−t) for a fatigue-precracked Charpy specimen is evaluated by means of an approximate formula. The onset time of crack initiation is experimentally detected using the strain gauge method. The value of KId is determined from the critical dynamic stress intensity factor at crack initiation. A KId value for a high-strength steel is obtained using this method at a stress-intensity-factor rate (K̇Id) greater than 106 MPa m/s.