New Insight Into Crack-Healing Mechanism via Electropulsing Treatment

Abstract

A combination of experiment and numerical simulation was employed to study the healing mechanism of fatigue crack via a novel route of electropulsing treatment (EPT) named dual-step EPT processing. By applying cyclic loads, similar cracks were generated in 316L stainless steel samples. Then, cracked specimens were subjected to electropulsing treatment under different conditions in order to find the optimum EPT condition to effectively heal the crack. The geometry of the fatigue crack before and after EPT was investigated in 3D by Micro-CT. SEM-EBSD was used to evaluate the microstructure of the healed region. To understand the dominant mechanism of crack healing by EPT, the temperature and stress/strain fields were evaluated by the finite element method (FEM) considering non-uniform Joule heating. The results demonstrate that complete crack healing requires a balanced combination of melting and compressive stress as well as increased peak current density regarding the reduced crack length. The simulations also suggest that Joule heating alone is sufficient to induce the observed melting in the examined samples. The fatigue crack after EPT was found to be effectively healed, as indicated by the similar crack growth rate compared with the samples without electropulsing treatment. In addition, a refined microstructure can be achieved after EPT.