Abstract
On this paper we describe the methods for estimating the depth of lager slit flaws which appear on surface and bottom such as longer lack of penetration in root and longer crack which appears on surface and bottom and so on. We analyzed the informations from the depth scan and picked up such seven methods for estimating the depth of that slit flaws as D_<max> method. D_x method, D_e method, D_s method, X_<max> method, X_e method, and X_s method. In testing we used such a probe that the beam angle 45 degrees, the frequency 2 Mhz and the crystal size 20mm×22mm. The general method for estimating the flaw size by the scanning distance (we called D_e method) was not effective to estimate the depth of that slit flaws. X_<max> method which is by using the relations between X_<max> and the depth of flaws was not so effective, too, by that probe. X_<max> varies with the depth of flaws to lager depth by using other angle beams except 45 degrees. So the X_<max> method may be effective to estimate the depth of that slit flaws. X_<max> is the distance from flaws to the probe index in the maximum echo height. We recommend the method by the maximum echo height (we called D_<max> method) for estimating the depth of that slit flaws, in spite of the limitation of estimating the depth. We examined the D_<max> method theoritically.
