Using open-ended rectangular waveguide probe for detection and sizing of fatigue cracks in metals - Electronics Letters

Introduction: There are several electromagnetic techniques that can be used for detecting surface-breaking cracks in metals, including potential drop, AC field measurement and eddy current methods. Each method possesses its own advantages and limitations in a specific application. In recent years, the use of microwaves has shown an increasing potential and success as a new technique for non-destructive detection and evaluation of defects in metals. In this technique, the metal surface is scanned by an open-ended waveguide probe while its standing-wave characteristics are monitored using a slotted waveguide and a diode detector. The crack detection and sizing in this technique has been successfully demonstrated in the case of a long crack [1]. The growth of fatigue in metals is a stochastic process, and starts by creating short-breaking cracks of semi-elliptical shape. In this Letter we outline the principles of using open-ended waveguide probes for the detection of cracks in metals, examine signals associated with elliptical cracks and discuss the method developed to invert crack signals to crack dimensions.