Very high cycle fatigue of TC4 titanium alloy under variable stress ratio: Failure mechanism and life prediction. (November 2017)

• Record Type: Journal Article
• Authors: Li, Wei; Zhao, Hongqiao; Nehila, Abdelhak; Zhang, Zhenyu; Sakai, Tatsuo
• Is Part Of: International journal of fatigue. Volume 104(2017)
• Page Start: 342
• Page End: 354
• Publication Date: 2017-11
• Subjects: Very high cycle fatigue -- Granular bright facets -- Nucleation and growth -- Theory and modeling -- TC4 titanium alloy; Materials -- Fatigue -- Periodicals; Materials -- Fatigue; Periodicals; 620.1122
• DOI: 10.1016/j.ijfatigue.2017.08.004
• Languages: English
• ISSNs: 0142-1123

Abstract

Graphical abstract: (a) Duplex S–N curves associated with surface and interior failures under R = −0.3, 0.1, 0.3 and 0.5, and only related to surface failure under R = −1; (b) Surface crack nucleation area; (c) Facets with slip lines at the surface crack nucleation area for R > 0; (d) Interior failure associated with GBF and fisheye in the VHCF regime; (e) Facets with slip lines at the GBF area. Highlights: The interior failure mechanism involving facets → GBF → fish-eye → final failure was elucidated. An energy-based crack nucleation life model associated with failure mechanism was established. A VHCF life prediction approach involving crack nucleation and growth behavior was developed. Abstract: Axial loading tests with variable stress ratio were performed to investigate the very high cycle fatigue property of TC4 titanium alloy, and a life prediction approach associated with failure mechanism was proposed. The interior failure process is characterized as: (1) occurrence of slip lines or bands on partial α grains, (2) nucleation of micro-cracks within some α grains, (3) coalescence of micro-cracks and formation of granular bright facets, (4) stable macro-crack growth within fisheye (5) unstable crack growth outside fisheye and (6) momentary fracture. The validity of approach is confirmed by the good agreement between predicted and experimental results.