Abstract
The shape of surface crack is estimated using infrared stress analysis system. The length of the surface crack, 2c, is measured directly using this method, but it is difficult to estimate the depth of the surface crack. For this purpose, tests are conducted changing the frequency of the cyclic load from 20 [Hz] to 5 [Hz] in four steps. By the cyclic loading, the ellipsoidal area appears between two crack tips of a surface crack. It means the change of the summation of the normal stress. By multiplying the stress value to the ellipsoidal area the depth of surface crack, a can be evaluated. For 5 [Hz] cyclic loading, it is found that the volume changes systematically with the change of the aspect ratio, a/c, of the surface crack. And for a/c=0.57 specimen, it is observed that this volume changes linearly with the change of 2c value. Based on these experimental results, a basic method to estimate the shape of the surface crack is proposed.
