Examination of discontinuties in welds by steroradiography

Stereoradiography, unlike normal incidence radiography or ultrasonic inspection, permits direct three dimensional observation of internal flaws. Stereoradiography entails obtaining an x-ray exposure at two known positions of the specimen with respect to the x-ray tube and viewing the stereo-pair through a stereo-viewer (stereoscope). By accurately measuring the parallax differences resulting from the specimen (or x-ray tube) shift, one may calculate the weld flaw's depth below the plate surface using photogrammetric principles. An accurate and efficient technique for obtaining stereoradiographs was developed in this investigation. To evaluate this technique, ten pores in a defective weldment were measured at three different times. The results were compared to determine how well an observer could reproduce his measurements. The weld was sectioned, and the actual pore depths were measured directly. The results were compared to the stereoradiographically measured depths to determine the accuracy of the technique. It was found that stereoradiography could measure depth below a surface to within 0.04 in. of the actual pore depth. Also, the average stereoradiographically measured depths were reproducible within 0.04 in. In both cases, these errors are insignificantly small for engineering purposes