Crack Length Quantification Based on Planar Eddy-Current Sensor Array and Two-Dimensional Image

Abstract

Eddy-current (EC) testing is an effective electromagnetic non-destructive testing (NDT) technique. Planar eddy-current sensor arrays have several advantages such as good coherence, fast response speed, and high sensitivity, which can be used for micro-damage inspection of crucial parts in mechanical equipments and aerospace aviation. The main purpose of this research is to detect the defect in a metallic material surface and identify the length of a crack using planar eddy-current sensor arrays in different directions. The principle and characteristics of planar eddy-current sensor arrays are introduced, and a crack length quantification algorithm in different directions is investigated. A damage quantitative detection system is established based on a field programmable gate array and ARM processor. The system is utilized to inspect the micro defect in a metallic material, which is carved to micro crack with size of 7 mm (length)×0.1 mm (width)×1 mm (depth). The experimental data show that the sensor arrays can be used for the length measurement repeatedly, and that the uncertainty of the length measurement is below ±0.2 mm.