Design and analysis of a GMR eddy current probe for NDT

Defect detection in metallic plates represents an important issue in metal industry, because its potential use in quality control process. Eddy current testing is one of the most extensively used nondestructive techniques for inspecting electrically conductive materials. The purpose of this paper is to present an eddy current testing system for surface defect detection in conducting materials using a giant magnetoresistive (GMR) sensor. An alternate magnetic field is produced by a solenoid and eddy currents are generated in the material under test. The GMR sensor was mounted inside the coil and the arrangement was adapted in the axis of a vertical machining center. In order to validating the measurement device, defects were induced by cracks machined in workpieces made of aluminum. Thus, the parts were scanned with the sensor prototype and a method to estimate the width and depth of the induced defects was proposed after analyzing the output voltage signal.