Evaluating the contraction value of ferromagnetic material at early fatigue loading stage using magnetic flux leakage signature

Abstract

This work focuses on the investigation to evaluate a material parameter, namely a contraction value ψ, at failure in estimating the fatigue life of ferromagnetic steel based on magnetic metal memory method. It begins with specimen preparation made from mild carbon steel and it was machined as specified in the ASTM E467-01 standard. These cyclic tests were performed using the 25-kN servo-hydraulic machine with the applied axial loading levels were at 60% UTS and 70% UTS. The magnetic flux leakage was then measured at every hour of the load applied, and the nature of change of magnetic leakage intensity Hp over the surface of the specimen. A further analysis on the collected signals or pattern was carried out based on the Hp distribution and its gradient at dHp/dx, and both parameters were later being used to estimate total loading time before specimen failure. A further analysis on the collected signals or pattern was carried out based on the Hp distribution and its gradient at dHp/dx, and both parameters were later being used to estimate total loading time before specimen failure. At every hour of loading cycles, the fatigue life of the specimen is estimated using the specific calculation of this MMM approach.