Application of Multi-microprobe DC Potential Difference Method to Residual Life Prediction in High-temperature Fatigue of Austenitic Stainless Steel: Effects of Multiple-site Small Cracks' Growth on Potential Difference

Abstract

The present authors have proposed a new DC potential difference method using multi-microprobes and showed that the method can successfully make the residual life estimation for high temperature fatigue of an austenitic stainless steel JIS SUS316L at high temperatures of 765 to 923 K where multiple-site small cracks cause fatigue fracture. In order to clarify the effects of the growth of the multiple-site small cracks on the variation of potential difference values measured, the present paper has performed FEM steady-state current analyses as well as experimental analyses. The results showed that the growth of multiple-site small cracks following the Paris-type fatigue law can bring about the knee point of the diagram of the relationship between the standard deviation σ_V of normalized potential difference V/V₀ and normalized number of fatigue cycles N/N_f which has been proposed by the present authors.