Experimental Investigations to Evaluate the Validity and Performance of NDT Procedures for In-Service Inspections
During multipass welding, cumulative and repetitive thermal phenomena may lead to development of cracks that can seriously compromise the quality of the welded joint. The use of Non-Destructive Testing methods is needed for the in-service inspection of the welded joint quality. To reliably evaluate the performance of an NDT procedure for in-service inspections, different types of artificial defects are used for this study. They have to be representative enough in comparison with the real service defects. For instance, thermal crack was realistically created by machining in a welded joint achieved by MAG welding deposition of melted SG3 wire on E36-3 steel, this case study being widely met in the crane industry. The approach consists of comparing two different ultrasonic techniques (Normal beam inspection and Angle beam inspection) in order to evaluate their performance in detecting and determining the size of well-known defects. Despite the difficulty in developing and interpreting the on-screen signals, caused by uncertainty in measuring the defect size, better results have been achieved when the angle beam inspection technique has been applied for the in-service inspections.
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