Microwave nondestructive detection method of circumferential defect: Numerical simulation and mode variation effects

Recent studies have shown that microwave nondestructive testing promises to be a suitable method of long pipe inspection. Since pipes are excellent waveguides, this technique is more appropriate for detection of inner defects which are produced inside the pipes. In this connection, circular TM-modes can be applied for circumferential crack detection. In this study, to show defect sensitivity of the other higher modes, a traditional mode-converter which is a transition between rectangular and circular waveguide is simulated by the finite element method analysis. Propagation of three circular TM_01, TM_11and TM_21-modes in the mode converter which is connected to a pipe with a circumferential crack is investigated. The result of simulation indicates that response of the TM_11-mode to the circumferential flaw is better than the other circular TM-modes for typical detection. Obtained results show that this method is an effective way to detect defects inside pipes and can be applied for industrial detections.