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A study on fretting friction evolution and fretting fatigue crack initiation for a spherical contact
KTH, Superseded Departments, Solid Mechanics.ORCID iD: 0000-0001-6896-1834
KTH, Superseded Departments, Solid Mechanics.
2004 (English)In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 26, no 10, 1037-1052 p.Article in journal (Refereed) Published
Abstract [en]

A new design for fretting experiments is presented. The normal and tangential contact loads as well as the specimen bulk stress are separately controlled. The separate control of load systems enables more accurate simulations of the fretting situations in component interfaces. Also, the influence of the salient parameters can be investigated individually. The initial test series comprised a spherical indenter and constant normal load and bulk stress. The evolution of the slip zone coefficient of friction at a spherical fretting contact was evaluated in four different ways. For two of these methods new equations were derived. The importance of a correct coefficient of friction and the advantages of each evaluation method are discussed. The experimental results were evaluated with respect to fretting fatigue crack initiation. Five multi-axial fatigue criteria were evaluated and ranked with respect to their ability to predict fretting fatigue initiation properties. The endurance limits of all criteria were too high as compared to the experimental fretting fatigue endurance level. A qualitative explanation for the discrepancy was found in the surface profile of the slip zone.

Place, publisher, year, edition, pages
2004. Vol. 26, no 10, 1037-1052 p.
Keyword [en]
fretting fatigue; fretting experiment; friction evolution; multiaxial fatigue; fatigue initiation
National Category
Engineering and Technology
URN: urn:nbn:se:kth:diva-6421DOI: 10.1016/j.ijfatigue.2004.03.010ISI: 000223223300002ScopusID: 2-s2.0-3042815179OAI: diva2:11126
QC 20100827 QC 20110922Available from: 2006-11-23 Created: 2006-11-23 Last updated: 2011-09-22Bibliographically approved
In thesis
1. Life prediction and mechanisms for the initiation and growth of short cracks under fretting fatigue loading
Open this publication in new window or tab >>Life prediction and mechanisms for the initiation and growth of short cracks under fretting fatigue loading
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Fretting fatigue is a damage process that may arise in engineering applications where small cyclic relative displacements develop inside contacts leading to detrimental effects on the material fatigue properties. Fretting is located in regions not easily accessible, which makes it a dangerous phenomenon. It is therefore important to be able to make reliable predictions of the fretting fatigue lives.

The work presented in this thesis has its focus on different aspects related to fretting fatigue in the titanium alloy Ti-17. A fretting experiment was developed which allowed for separate control of the three main fretting loads. Initially, the evolution of the coefficient of friction inside the slip region was investigated experimentally and analytically. Subsequently, 28 fretting tests were performed in which large fatigue cracks developed.

The fretting tests were firstly evaluated with respect to fatigue crack initiation through five multiaxial fatigue criteria. The criteria predicted a too high fretting fatigue limit. A possible clue to the discrepancy was found in the fretting induced surface roughness with the asperity-pit interactions.

The fatigue growth of the large fretting cracks was numerically modelled through a parametric crack growth procedure. The predicted lives were compared to the experimental outcome. The numerical simulations showed that linear elastic fracture mechanics was an appropriate tool for the prediction of fretting fatigue propagation lives in the long crack regime.

Fatigue cracks spend most of their propagation life in the small crack regime. The possibility of modelling the small crack behaviour is therefore very important from the engineering point of view. The fatigue growth of through thickness short cracks was studied experimentally and numerically in the four-point bend configuration. It was found that linear elastic fracture mechanics and closure-free material growth data furnished conservative estimates for cracks longer than 50 μm.

One method to improve fretting fatigue life is to shot peen the contact surfaces. Experimental results on fretting life with or without shot peening were simulated. The fatigue life enhancement in shot peened specimens could be explained by slower crack growth in the surface material layer with residual compressive stresses.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. 29 p.
Trita-HFL. Report / Royal Institute of Technology, Solid mechanics, ISSN 1654-1472 ; 0423
Fretting fatigue; Fretting experiment; Friction evolution; Fatigue crack initiation; Fatigue crack growth; Short crack; Non-destructive testing; Acoustic emission; Potential drop; Shot peening; Stress relaxation; Crack closure; Finite element method; Titanium alloy.
National Category
Mechanical Engineering
urn:nbn:se:kth:diva-4185 (URN)
Public defence
2006-12-06, F3, Lindstedtsvägen 28, KTH - Stockholm, 10:00

QC 20100827

Available from: 2006-11-23 Created: 2006-11-23 Last updated: 2013-01-14Bibliographically approved

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