Research on the Detection Mechanism of Crack with Corrosion Using Eddy Current Pulsed Thermography

In the running process of locomotive, many tiny cracks emerge on the wheel tread due to the rolling contact between wheel and rail. On account of being exposed to complex environment, the crack flank will be corroded and filled with a third medium such as corrosion, then contact with each other under cyclic tensile or compressive stress, leading to local closure of the crack region, which affects the physical properties of the crack, showing low electrical conductivity for example. This is a new phenomenon that conventional electromagnetic detection method might not be capable of detecting such defects effectively. This paper aims to detect crack with corrosion on the basis of eddy current pulsed thermography (ECPT), establish a composite crack model to explore the performance of ECPT over low conductivity crack, and the influence of varying electromagnetic properties to ECPT will be studied as well. Crack detection principle was introduced first, and numerical simulations were conducted to detect crack with corrosion, transient and spatial temperature distribution characteristics were extracted during heating and cooling stage, experiments were designed and conducted to verify the accuracy and consistency.