Quantitative evaluation of cumulative plastic damage for ferromagnetic steel under low cycle fatigue based on magnetic memory method

Abstract

Cumulative plastic damage caused during the low cycle fatigue (LCF) regime may seriously undermine the safety of the steel members and even lead to serious industrial accidents. Magnetic memory method (MMM), as a novel nondestructive testing technology, has been developed to evaluate the fatigue damage for the ferromagnetic material, but there is the lack of a quantitative description exists for the relationship between magnetic memory signals and cumulative plastic damage yet. In this paper, the strain‐based Jiles–Atherton hysteresis model under cyclic load during the LCF regime was established. Meanwhile, the LCF tests for S355 steel were performed, and the HSF signals on the surface of the specimen were collected under different loading cycles. Finite element (FE) simulations for coupling magnetic memory signals and cumulative plastic strain were carried out by the strain‐based Jiles–Atherton hysteresis model. Comparing with experimental results verifies the feasibility and accuracy of the FE method. The results indicate that the slope of the HSF signals fitting curve, K, as a characteristic parameter, has an exponential decrease as the cumulative plastic damage D increases. A general quantitative expression of the magneto‐damage model was built by discussing the influences of different factors on the K–D relation curves. It can be proved by verification that the magneto‐damage model provides a direct way for the quantitative evaluation of the cumulative plastic damage for the low‐carbon steel under LCF.