Eddy Current Sensor with a Novel Probe for Crack.pdfVIP

Eddy Current Sensor with a Novel Probe for Crack Position Detection Peng Xu Department of Electrical and Electronic Engineering, Saga University, Japan Katsunori Shida Department of Electrical and Electronic Engineering, Saga University, Japan Abstract—An eddy current testing probe is researched to detect crack. The probe is composed of double uneven step distributing planar coils. When a crack in test metallic surface is in measurable range beneath probe, its position can be detected directly and quickly in non-scanning detection mode. This static crack detection can reduce measurement work and advance test efficiency greatly compared with the traditional dynamic crack detection by scanning. Experimental results show that the difference inductance of two probe coils is approximately linear with crack position in measurable range. By doing curve fitting for the dependence of difference inductance on crack position based on the least squares principle, an expression of crack position estimation is finally deduced and its estimating error is studied. Index Terms—ECT probe, planar coil, crack detection, inverse problem I. INTRODUCTION Eddy current testing (ECT) is one of several non-destructive testing (NDT) methods that use the principle of electromagnetism as the basis for conducting examinations. As a NDT tool the ECT can perform in a variety of inspections, and the crack detection of metallic structural frames is an important application of ECT. Nowadays the crack detection is requested to not only detect the existence of a crack but also obtain more detail information including its position, shape, length, direction, and material parameters [1] [2]. The crack position is usually detected by using ECT probe to scan the test metallic surface point by point. Obviously the scanning detection is the dynamic detection that performs a mass of measurement work. So we research an ECT probe which can detect crack in the non-scanning detect