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Vol.7 No.2previous AASP15 (106-107-108-109-110-111)-AA112-113 NT71

Academic Articles
Regular Paper Vol.7 No.2 (2015) p.172 - p.178
 

Non-Destructive Evaluation of Multiple-site Small Cracks in Low Cycle Fatigue of Austenitic Stainless Steel by Four-point Probe DC Potential Difference Method

 
Shio NAKANISHI1, Takayuki SUZUKI2, Yuji NAKASONE1
 

1 Tokyo University of Science, 6-3-1 Niijuku, Katsushika-ku, Tokyo 125-8585, Japan
2 National Institute of Advanced Industrial Science and Technology, 1-2-1 Namiki, Tsukuba-shi, Ibaraki 305-8564, Japan

 
Abstract

This study has investigated multiple-site small cracks in the low cycle fatigue of SUS316L at 873K in air by using the four-point probe DC potential difference method. Small probes with 1-mm spacing between the electrodes were used in order to evaluate small cracks of some hundred micrometers. Morphology of the cracks was evaluated by standard deviation of potential difference σV which detected by the probes and by the crack density by laser microscopy. As a result, it was shown that σV monotonically increased with increasing number of strain cycles and fatigue process was classified into four stages. Furthermore, statistical analysis showed that the cracks initiated at random sites in early stage. However, the randomness was diminished and σV increased significantly with growth and coalescence of the cracks. These results revealed that standard deviation of normalized potential difference could evaluate initiation, growth and coalescence of multiple-site small cracks in each stage.

 
Keywords
Low cycle fatigue, Austenitic stainless steel, Multiple-site small cracks, Crack growth and coalescence, Four-point probe DC potential difference method, Statistical analysis
 
Full Paper: PDF EJAM Vol.7No.2 pp.172-178 "Non-Destructive Evaluation of Multiple-site Small Cracks in Low Cycle Fatigue of Austenitic Stainless Steel by Four-point Probe DC Potential Difference Method"
Article Information
Article history:
Received 2 December 2014
Accepted 3 July 2015