Effect of machined surface texture on fretting crack nucleation under radial loading in conformal contact

• Published in: Tribology international Vol. 153; p. 106575
• Main Authors: Gu, Huiqing, Jiao, Li, Yan, Pei, Liang, Jiabin, Qiu, Tianyang, Liu, Zhibing, Wang, Xibin
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.01.2021; Elsevier BV
• Subjects: Compacted layer; Conformal contact; Contact angle; Contact force; Crack initiation; Crack propagation; Fatigue cracks; Fatigue failure; Fatigue life; Fatigue tests; Fracture mechanics; Kurtosis; Machined surface texture; Milling (machining); Nucleation; Partially stabilized zirconia; Radial fretting; Skewness; Slip; Surface layers; Texture; Titanium alloys; Titanium base alloys; Zirconium dioxide; Compacted layer; Radial fretting; Conformal contact; Machined surface texture
• ISSN: 0301-679X; 1879-2464
• DOI: 10.1016/j.triboint.2020.106575

This paper presented the influence of machined surface texture on fretting cracks behaviors of Titanium alloy Ti–6Al–4V under radial loading in conformal contact. The contacted holes of specimen were machined with combined helical and flank milling before fretting fatigue tests, and a special fretting fatigue test apparatus was proposed to focus on conformal contact fretting fatigue (CCFF) test under radial loading. The test results showed that all the specimens failed at the contact area where characterizes an inner obtuse angle between the material flow direction (or cutting direction) and the direction of the tangential component of the contact force. The area with higher surface skewness and kurtosis values was also prone to nucleate fretting fatigue crack. These results suggested that the corresponding machining conditions in hole-making and surface strengthen processes should be adjusted to guide the production of surface texture properties, in terms of obtaining desirable lower skewness and kurtosis features to relieve nucleation of fretting cracks. Additionally, the debris in conformal contact tended to aggregate towards the partial slip zone (PSZ) due to the conformal geometry and form a compacted layer in the gross slip zone (GSZ) subjected to radial loading. These characteristics exacerbated and alleviated fretting damage in the PSZ and GSZ, respectively. In this research, a set of suitable milling parameters for the hole flank milling process in terms of prolonging fretting fatigue life were also defined. [Display omitted] •A test apparatus for conformal contact fretting fatigue under radial load was proposed.•Obtuse angle between material flow direction and the direction of the tangential component of the contact force was apt to nucleate crack.•Higher surface skewness and kurtosis value was prone to nucleate fretting crack.•The compacted debris layer in the gross slip zone alleviated fretting damage.