Demonstration of the applicability of nondestructive microwave testing to the long-range inspection of inner-surface cracks in tubes

Abstract

This study evaluated the applicability of nondestructive microwave testing method for the long-range detection of inner-surface cracks in metallic tubes. Two seamless straight tubes 7 m in length and 23.0 mm in inner diameter were prepared, and artificial circumferential slits penetrating the tube walls were introduced. A probe to propagate microwave inside the tube, designed based on three-dimensional finite element simulations, was attached to an end of the tube, and the reflections of the microwave propagating inside the tube were measured using a network analyzer. The experiments confirmed clear reflections due to the slits situated 6 m away from the probe. Furthermore, imposing a signal processing method to compensate for the dispersion of the microwave clarified the reflections and enabled the slit to be localized quantitatively from the time-of-flight of the reflections.