THE EXPERIMENTAL INVESTIGATION OF DEFORMATION AND OPENING DISPLACEMENT AT A CRACK-TIP

The crack-tip opening displacement (CTOD) of four classes of steel with different yielding strength and hardening ability have been measured by indirect and direct methods to investigate the changes of CTOD with load and material properties. In general the values of CTOD obtained from the indirect method are larger than those obtained from direct methods. The differences increase with the decrease of CTOD and with the increase of yielding strength, as is the result of non-plastic hinge deformation mechanism around the crack tip. According to the results of experiments the deformation mechanisms around the crack tip are discussed. Based on the suggested deformation mechanism in this paper, some appropriate proposals on the methods of measuring CTOD are given also.