Constract of Defect Sensitivity of Artificial Grooves and Holes in ET for Tubes

It is quite a important problem for design organizations and use units to choose grooves or holes as artificial discontinuities in ET for tubes. In this paper, first, through theoretical analysis, the sensitivity contrastive analysis is made between a groove and a hole, the size of the groove is 3.0 mm (length)× 0.075 mm (width)×0.050 mm (depth), the diameter of the through hole is 0.3 mm. The theoretical analysis indicates that: when the frequency is higher than a certain value, the sensitivity of the groove is higher than the hole; when the frequency equals the value, the sensitivity of the two equals; when the frequency is lower than the value, the sensitivity of the groove is lower than the hole. And finally, several experiments using the external through coil, internal through coil and pen probe have been done, and it is confirmed that the results of the theoretical analysis are right.