Three-dimension flaw detection for the welded seams of pressure vessels

This article deals with the three-dimensional analysis of internal flaws occurring in the welded seams of pressure vessels so as to determine the real location of the defects. For this purpose stereoscopic twin radiographs were used. Owing to the fact that radiographs are taken with films in circular form whereas the films have to be assessed in the flat condition, it is necessary to establish the relevant analytic relation between the circular and the flat film. To this end some equations were first established for the image points of the assumed flat film and that of the circular film, leading to the relevant formulae for ascertaining the spacial point location of the defect in the welded seam. Defects of different locations bring about different photocouple-points. The real location of the defect can be determined through its coordinates, Z_A, X_A and Y_A obtained through film observation and calculation.