Quantitative detection of lamination defect in thin-walled metallic pipe by using circumferential Lamb waves based on wavenumber analysis method

Lamination defect is one of the common defects in the manufacturing process of seamless pipes. In this paper, the quantitative detection of a lamination defect in thin-walled metallic pipe using circumferential Lamb waves is studied. To interpret the received time-domain signals and extract useful information about the lamination defect, wavenumber analysis is performed on these signals. A three-dimensional finite-element model is established using Matiab and ABAQUS commercial software. Owing to the processing technique, an aluminum ring structure with a three-quarters circumference is considered to represent the metallic pipe. The lamination defect constructed in the model is a "zero-volume" crack, which stretches from theta = 180 degrees to 270 degrees and locates in the mid plane of the wall. A five-cycle 0.41-MHz sinusoidal tone-burst signal modulated by a Flaming window is carefully chosen to generate the appropriate excitation wave, in CL0 mode. According to the received signals, the conclusion that the incident CL0 mode interacts with the lamination defect for numbers of times can be obtained. The space-amplitude curve of incident waves is also depicted to reveal the amplitude distribution of incident waves. A fully non-contact experimental platform that adopts an electromagnetic acoustic transducer as a transmitter and a laser ultrasonic inspection system as a receiver is set up to verify the finite-element model. Three different wavenumber analysis methods are performed on the wavefield signals to explain the detect ability of the lamination defect separately through both numerical and experimental studies. It can be concluded that, from the variation of wavenumber, the continuity of structure can be deduced. Not only can the location be calculated with an error of less than 10%, but the profile of the lamination defect can also be imaged. It is also found that very good consistency exists between numerical and experimental results.