Study for Crack Detection Technique on Black Color Ceramics using FID

A non-destructive testing technique for a crack existing randomly on a ferrite surface has been developed. Wher the sample is immersed into the volatile solvent, the solvent penetrates into the crack. The surface of sampl? becomes dry quickly, however the solvent remains in the crack and evaporates slowly. The crack is detected independently its position by detecting the evaporating gas from the crack. A FID (flame ionization detector) iE used to detect the extremely thin solvent gas. The optimum treatments from immersion treatment to sealing treatment are studied using several samples with the crack width from 0.003 mm to 0.06 mm. A lot of cracks ar? tested using the experimental apparatus. Experimental results show that a linear relationship is established between crack width and S/N ratio, and the detectable crack length varies inversely with the crack width, fot example in case the surface area is 250 mm2, the minimum detectable length with crack width 0.05 mm is 0.3 mm and that with 0.003 mm is 1.4 mm.