Simulation and analysis of the effect of tensile stress on defect quantification of ferromagnetic materials based on ECPT

Aiming at the problem of low defect quantification accuracy caused by the neglect of the effect of tensile stress on the permeability of ferromagnetic materials in the process of defect detection of ferromagnetic pressure equipment by eddy current pulsed thermography (ECPT), this paper combines the force-magnetic coupling relationship, electromagnetic induction law and Joule's law to simulatively investigate the influence of elastic tensile stress on defect quantification in different directions and depths by ECPT. The results show that the maximum permeability of the defects with different orientations increases with the elastic tensile stress growing. The maximum permeability at defect increases with the depth of the horizontal direction of defect. Meanwhile, it is not sensitive to the change of the depth of the vertical direction of defect. In the process of ECPT defect quantification, the slope of the horizontal defect depth quantification curve based on the temperature difference increases with the stress. The standard deviation of the horizontal defect quantification fitting curve is lower than 0. 3 ℃ and the coefficient of determination is higher than 95%. As a result, the fitting effect is good. The vertical defect depth quantification curve based on temperature difference characteristics is less affected by stress.