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

The crack-tip opening displacement (CTOD) of four classes of steel wit h different yielding strength and hardening ability have been measured by indirect and direct methods to investigate the changes of CTOD wit h load and material properties. In general the values of CTOD obtained from the indirect method are larger than those obtained from direct m ethods. The differences increase with the decrease of CTOD and with th e 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 dis cussed. Based on the suggested deformation mechanism in this paper, so me appropriate proposals on the methods of measuring CTOD are given al so.