Evaluation of Fatigue Damage in 304 Stainless Steel by Measuring Residual Magnetic Field

Abstract

To demonstrate the feasibility of the passive magnetic NDT method for damage assessment of 304austenitic stainless steel, the residual magnetic field change of the 304 stainless steel specimensunder fatigue loads was investigated. The measurement was carried out using a fluxgate sensor and the magnetic characteristics were extracted for analysis of fatigue state. Then, the XRD test was carried out to investigate the mechanism of magnetic field changes and verify the reliability of the proposed method. The results show that the variation of the maximum gradient is consistent with theprocess of fatigue crack growth, which indicates that the fatigue damage can be estimated by residual magnetic field measuring. In future stage, how to distinguish the magnetic field changes derivedfrom martensite transformation or stress magnetization effect will be investigated.