Mechanism of Fatigue Crack Closure in Steel Under High-Density Pulsed Current

Abstract

This study is aimed at clarifying the mechanism of effectively healing fatigue cracks in steel; austenitic stainless steel, SUS304; and hot work tool steel, SKD61, using high-density pulsed current. The results show that the current concentration occurred at the crack tip for SUS304, and crack closure was observed near the fatigue crack tip. On the other hand, crack closure was observed at the notch tip in SKD61. The fatigue crack closure phenomena were verified by finite element analysis, revealing that contact pressure was applied behind the crack tip owing to local bending deformation associated with residual stress near the crack tip. For effective crack healing, it is necessary to bond the interface leveraging compressive stress and Joule heat generated at the crack tip during current application.