A DISCUSSION ON THE RELATIONSHIP BETWEEN THE IMPACT TOUGHNESS AND THE FRACTURE TOUGHNESS

The impact value (AK) measured with classic impact experiment of mechanical properties is a normal index from the five important basic mechanical properties for engineering, but it still has no definite physical meaning. By use of the advanced impact experimental machine, the load-deflection signals under impact loading have been measured. According to the load-deflection curve of 30CrMnSiA steel obtained by this method, the AK value could be divided into the elastic deformation work, the plastic deformation work, the crack forming work, the work of crack propagation and the work of unstable crack propagation. Therefore, we can obtain the expression for the continuous changing of stress and strain under impact load. In this experiment, specimens with three different breaches, U type, V type and linear grooving, are used and the dynamic fracture toughness value (KDIC) of 30CrMnSiA steel is treated and calculated which follows the measuring method of material static fracture toughness, as ASTM E399. The e