Influence of Object Physical Properties Instability on Edge Current Method Sensitivity

Abstract

The article contains results of a study of the eddy current transducer signal parameters from artificial defects against the background of the influence of stray parameters simulated on specially manufactured samples exposed to various external influences. The authors studied the added voltage change of eddy current prob depending on factors affecting the electromagnetic properties of steels. The results of the study were the determination of optimal excitation parameters and threshold values for discrimination levels of phase, amplitude and dynamic parameters when detuning from stray factors. The authors modeled stray parameters of eddy current testing in the form of temperature effects, effects of chemical reagents and plastic deformation of the surface layer. The researchers assessed the distribution of the temperature field, the time of chemical reactions and the composition of the reagents, as well as the geometric parameters of the deformable surface layer of the samples and their effect on eddy current prob added voltage. For the research, artificial defects were made in the form of thin cuts with an opening width of 0.2 mm, located in the stray parameter zone. The geometric dimensions of artificial defects were determined by the requirements for the amplitude of the transducer signals, which should not exceed the change in amplitude under the influence of a stray parameter on the time base, relative to the zero-value installed in the sample area not subject to the influence of external factors. The obtained results of the hodograph analysis when scanning with a clamp-on eddy current transducer made it possible to propose recommendations for detuning from stray parameters of various nature. This was done in order to increase the detectability of defects on objects with significant heterogeneity of the surface structure in the eddy current testing zones.