Simulation analysis of magnetic sensor for nondestructive testing by boundary element method

The use of a differential transformer-type magnetic sensor for nondestructive testing was simulated by boundary element analysis, taking the external electric secondary circuit, the eddy currents, and movements into account. The existence of an error caused by the narrow air gap is identified, an element subdivision method is proposed for decreasing the error, and this method is shown to be effective. The analytical results are shown to be in good agreement with the measurement results. It is shown that the output voltage pattern can be used to estimate the shape or size of a flaw