Abstract: The dynamic properties of DCB model under step loading were calculated by using the vibration model of the beam. The fundamental frequency, the pin displacement, the external work, potential and kinetic energy, the dynamic stresss intensity factor and dynamic energy release rate were formulated approximately. Furthermore, a simple and available expression to determine the initial dynamic fracture toughness by using the DCB model is obtaind.

Key words: step load, DCB model, dynamic stress intensity factor