Experiments on relationship between sensitivity of image quality indicator and defect size of welds

Slit-type defects, which are similar in shapes to such weld defects as incomplete penetration and lack of fusion, have been produced. Radiographs were produced by changing the direction of radiation from parallel direction to the defect plane to 30 degrees angle. These radiographs were examined to measure the relation between the finest detectable diameter of wire-type image quality indicator and the minimum detectable dimensions of slit-type defects. Observations on the distributions of image width of slit-type defects and transmission thickness indicate that the cross section of the finest detectable wire is almost equal to the minimum detectable cross section of slit-type defects, and the finest detectable wire diameter is almost equal to the average transmission thickness of slit-type defect