Development of ultrasonic methods for the testing of welds in thin sheets

Various ultrasonic methods were developed for the nondestructive testing of welds in thin sheets. The conventional ultrasonic methods are not suitable for such welds because of interference problems and difficulties in signal separation. A novel method, hitherto not reported in literature, was developed for the testing of a spot weld using Lamb waves. As spot weld is one of the most common welding forms, finding methods for its testing is of major importance. Up to now such welds have been tested by radiographic methods. Ultrasonic tests have many advantages over radiographic tests, in sensitivity, costs, health of workers etc. In radiographic methods it is impossiOle to conduct quantitative analysis of the weld size. The testing of welds on cylindrical surfaces ultrasonically required the modification of special methods. Tests of welds in thin-walled cylinders were made by using the immersion technique. All the methods used are based on theoretical background and literature survey. The sensitivity of the various methods was examined to derive the optimal conditions. For tests with surface waves, probes were designed and built, enabling the obtainment of Lamb waves. Immersion tank was designed and built for immersion tests. (Author)