Eddy current testing probe composed of double uneven step distributing planar coils for crack detection

Abstract

A novel eddy current testing probe composed of double uneven step distributing planar coils is researched to be used in crack detection. Because of the novel coil structure, the probe can not only detect the crack existence but also the crack position directly and quickly in measurable range of test metallic surface in non-scanning detection mode. This static crack detection can reduce measurement work and advance test efficiency greatly compared with traditional dynamic crack detection by scanning. The eddy current sensor using this probe can realize the line detection for defects which is improved from the traditional point detection. Experimental results show that in crack detection the difference inductance of double probe coils is approximately linear with crack position in measurable range. Through curve fitting of the dependence of difference inductance on crack position based on the least squares principle, finally a formula of crack position estimation is deduced, and its estimation error is studied. © 2008 The Institute of Electrical Engineers of Japan.