An Evaluation Method for Near Inspection Surface Defect Tested by the TOFD Secondary Wave

The dead zone of inspection surface could not be avoided when using TOFD technique due to the width of lateral wave. In order to solve the problem, the block with given depth of artificial defect, which were respectively inspected by traditional and secondary wave TOFD technique. The result, compared with the different images, was that the defect near the inspection surface was hard to be quantified as well as detected by the former of two TOFD methods. However, the defect could be obviously recognized and accurately measured by the latter method. So the traditional TOFD inspection accompanied with secondary wave TOFD was the better way to avoid the dead zone near the inspection surface.