PURPOSE: To detect the shape and dimensions of a crack on the surface at a high accuacy by determining the surface length of the crack from the range of 2σ and the depth thereof from the area ratio thereof and the ratio of potential difference through approximation of the distribution of the potential difference ratio to the normal distribution.
CONSTITUTION: Direct current runs between A-A' from a D.C. power source (c) to measure a potential difference at upper and lower positions sandwitching a crack (a) between terminals 1-1', 2-2', 3-3'... and the results are inputted into a crack shape analyzer (f) through a micro voltometer (e) to compute the shape of the crack. In the analysis of the crack shape, the ratio V/V0 is obtained between a potential difference V0 without crack and a potential difference V after a crack develops to prepare a distribution of the potential difference ratio from which the shape and dimensions of the crack are determined. In approximation of the distribution of the potential difference ratio to the normal distribution, the surface length of the crack corresponds to the position of 2σ (σ: standard deviation). To determine the depth of the cracking, an equation of the cracking area S is established from a relationship of the ratio betwen the area S of the cracking and the total sectional area S0 thereof with the ratio of potential difference and calculated by substituting the surface length thereof previously obtained.
HAYASHI MAKOTO
SATOU YOSHIMI
SHIMIZU TASUKU
