Tensile stress effect on crack depth quantification in ferromagnetic materials using ECPT

Abstract

As one of the fast-developed NDT&E (nondestructive testing and evaluation) techniques, eddy current pulsed thermography (ECPT) is extensively used for crack detection and quantification in ferromagnetic pressure components. However, in the practical inspection, the stress has significant influences on the permeability while that haven’t been concerned. To improve the detection accuracy of crack measurement, this paper focuses on making clear the tensile stress effect on the crack depth quantification in ferromagnetic materials by ECPT. A theoretical analysis, including the ECPT theory, the stress equivalent field theory and the μ-Hσ curve, has been conducted and verified by experiments. The results show that the direction and magnitude of the stress have strong influences on the thermal features. And the tensile stress can increase the linear slope of crack depth quantitative curve. Further, probability of detection (POD) curves prove that the tensile stress enhances the detection capability of shallow cracks by ECPT.