Abstract: 510L steel is chosen to study how magnetic memory signals change during ferromagnetic material’s crack propagation process. To establish the relationship between the gradient Kmax of magnetic memory signals of the crack tip and its stress intensity factor KI, the magnetic memory signals in different regions on the test pieces are collected and analyzed, the stress intensity factors of crack tips are calculated, and the fatigue fracture surfaces are analyzed. The results show that the observed magnetic memory signal at the macro kerf of the test sample M(T) has larger amplitude than that at the zone of stress concentration of the crack tip. Both Kmax and KI increase exponentially when the fatigue cyclic accumulates. It proves that Kmax can be used to quantify the cumulative fatigue damage from the viewpoint of fracture mechanics. The features of magnetic memory signal, ΔHp(y) and Kmax, can quantify the damages of 510L steel after different service periods, and provide solid references for the remanufacturing.

Key words: Fatigue crack propagation, Magnetic memory testing, Remanufacturing, Stress intensity factor