Sizing technique for slots and surface cracks in metals

Abstract

After a crack on a metal surface has been detected, determining its width, depth, and length becomes an important practical issue for fracture analysis and repair considerations. Having used a novel microwave technique for surface crack detection, two methods for sizing are introduced, mamely a single frequency and a swept frequency method. The tradeoff between these two techniques is between hardware simplicity and high measurement accuracy, particularly when determining crack depth. The details-of these two techniques are given will several numerical and experimental results. The width of a crack is shown to be measured within ±20 percent. However, the crack depth, the most important parameter in crack sizing, is shown to be measured with an accuracy of better than 1 percent, independent of the accuracy of the width measurement, using the swept frequency technique. Keywords: crack characteristic signal, crack width, metals, microwaves, mondestructive evaluation, surface cracks, swept frequency