Physical principles of eddy current technique in mondestructive testing of metals

Following a general summary of the widely used nondestructive testing methods, the physical principles and the related instrumentation of the eddy current method, which Is an important application in metal industry, has been investigated in this thesis. The impedance of the test coil, being the most important component of the eddy current test systems, was formulated by a model of vector potential and also by a simulation of two circuits and the results numerically obtained, were compared to the experimental data from the literature. In order to demonstrate the basic functions and the working principles of an eddy current nondestructive test system and also to induce eddy currents in the inspected material for discontinuity detection, a laboratory prototype was constructed. Despite the simplicity of it's circuitry, the prototype exhibits the the basic functions expected from an actual eddy current test system.KEY WORDS : Nondestructive Testing, Eddy currents, Crack Dedector.