Distinguishing evaluation of plastic deformation and fatigue damage using pulsed eddy current testing

The vessels and pipes of nuclear power structures are subjected to complex forces. The structures suffer sudden loads that lead to plastic deformation and cyclic loads that result in fatigue damage. In practice, two types of microscopic damage may occur simultaneously. The effect of plastic deformation on material fatigue properties remains unclear, and there is a lack of effective methods to distinguish plastic deformation and fatigue damage. To address these issues, the fatigue life curve of 304 stainless steel is experimentally measured, and the influence of fatigue life due to the presence of plastic deformation under a certain load is investigated. It's identified that preset plastic deformation below 15% will increase the fatigue life of the structure. Additionally, a pulsed eddy current signal processing and reconstruction method based on the empirical modal decomposition (EBD) method is proposed. Finally, the pulsed eddy current signal characteristics of plastic deformation and fatigue damage are analyzed, and a distinguishing evaluation method of fatigue damage with preset plastic deformation is established.