Magnetic memory testing towards fatigue crack propagation of Q235 steel for remanufacturing

A crack propagation trial was performed on a Q235 steel M(T) sample to investigate the modifications in magnetic memory signals throughout the crack propagation procedure of ferromagnetic substances. Various detection lines were employed to gather and scrutinize magnetic memory signals under two-stage fatigue loading. The interrelation between the gradient value Kmax, the peak-to-peak value SP−Py, the stress intensity factor Ka, the extension of the sample 𝜀, crack length a, and the cyclic N was established. The findings indicate that the Hp(y) curves present a varied peak at the crack tip and in the notch, whereas the Hp(x) curve is linear. The magnetic signals display similar changes during two-stage fatigue loading, but the post-break state deviates. The fatigue process’s SP−Py shows three phases of fluctuation, escalation, and decline. Throughout the period of fatigue crack growth, Kmax and 𝜀 rise exponentially, Ka ascends linearly, and a shows linear changes. The characteristics of magnetic memory signals can measure harm after varying service periods and offer robust foundations for remanufacturing.