The amplitude-sensitive eddy current method for investigation of the plastically deformed metal zone beneath the indent obtained by ball indentation

Abstract

The paper presents the analysis of the results of plastic deformation zones obtained by the ball indentation into the surface of a non-magnetic metal plate using the amplitude-sensitive eddy current method. Calculation and experimental methods were used in the research. A two-dimensional finite-element model of an eddy current probe installed above a local plastically deformed zone on the metal plate surface was developed. The finite-element modelling of the electromagnetic field of eddy currents induced in the aluminium plate during multi-frequency excitation was made. It is found that the amplitude-sensitive eddy current method is appropriate not only to estimate the plastic deformation zone propagation depth, but also to detect a zone with the maximum stress values beneath the indent (hydrostatic core zone). An experimental verification of the proposed model was done. The specific zones in the deformed metal beneath the indent were detected by the eddy current method and the hydrostatic core size was evaluated.