Non‐destructive evaluation of fatigue damage and fatigue crack initiation in type 316 stainless steel by positron annihilation line‐shape and lifetime analyses. Issue 7 (23rd December 2016)

• Record Type: Journal Article
• Authors: Uematsu, Y; Kakiuchi, T; Hattori, K; Uesugi, N; Nakao, F
• Is Part Of: Fatigue & fracture of engineering materials & structures. Volume 40:Issue 7(2017:Jul.)
• Page Start: 1143
• Page End: 1153
• Publication Date: 2016-12-23
• Subjects: fatigue crack initiation -- fatigue damage -- non‐destructive testing -- positron annihilation lifetime spectroscopy -- positron annihilation line‐shape analysis -- stainless steel; Materials -- Fatigue -- Periodicals; Fracture mechanics -- Periodicals; 620.1123
• DOI: 10.1111/ffe.12572
• Languages: English
• ISSNs: 8756-758X

Abstract

Abstract: Rotating bending fatigue tests were conducted using type 316 stainless steel. The fatigue tests were periodically terminated, and fatigue damage and fatigue crack initiation were non‐destructively and sequentially evaluated by positron annihilation line‐shape and lifetime analyses. The counter‐jig and anticoincidence methods were used for positron annihilation line‐shape and lifetime analyses, respectively, to enhance the analytical precision. The fatigue crack lengths were monitored by a plastic replication technique, and related to the parameters in both analyses. S ‐parameter obtained in the line‐shape analysis increased with increasing fatigue damage, while it was difficult to detect fatigue crack initiation and subsequent small fatigue crack growth. That was because the precision of line‐shape analysis was limited. On the other hand, both fatigue damage and fatigue crack initiation were successfully detected by lifetime analysis. Positron annihilation lifetime also increased with increasing fatigue damage, and lifetime was longer at the notch root with fatigue crack than at the smooth section without crack. It was considered that the precision of lifetime analysis was high enough to detect high dislocation density areas at the fatigue crack tips.