Microwave Detection of Stress-Induced Fatigue Cracks in Steel and Potential of Crack Opening Determination Using a New Phase Sensitive Approach Based on a Waveguide Magic Tee

Abstract

Detection and evaluation of surface cracks in metals is an important facet of nondestructive testing and evaluation (NDTE namely, dominant mode, higher-order mode and open-ended coaxial lines [1–4]. Evaluation of crack properties (crack width, depth, load estimation or other useful information) is the next step in fully determining the threat that a crack may pose to a structure. Surface crack detection, using open-ended rectangular waveguides is primarily based on changes in the phase of the reflection coefficient at the waveguide aperture when a crack is scanned. Therefore, a phase sensitive system may be used for this purpose. The use of a magic tee based approach has the advantage of quick and interactive phase adjustments-adjustments are made immediately by the turn of a knob. In this way optimization is an easy and effective process.