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Influence of residual stresses from shot peening on fretting fatigue crack growth
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).ORCID iD: 0000-0001-6896-1834
2007 (English)In: Fatigue & Fracture of Engineering Materials & Structures, ISSN 8756-758X, E-ISSN 1460-2695, Vol. 30, no 10, 947-963 p.Article in journal (Refereed) Published
Abstract [en]

One method to improve fretting fatigue life is to shot peen the contact surfaces. Experimental fretting life results from specimens in a Titanium alloy with and without shot peened surfaces were evaluated numerically. The residual stresses were measured at different depths below the fretting scar and compared to the corresponding residual stress profile of an unfretted surface. Thus, the amount of stress relaxation during fretting tests was estimated. Elastic-plastic finite element computations showed that stress relaxation was locally more significant than that captured in the measurements. Three different numerical fatigue crack growth models were compared. The best agreement between experimental and numerical fatigue lives for both peened and unpeened specimens was achieved with a parametric fatigue growth procedure that took into consideration the growth behaviour along the whole front of a semi-elliptical surface crack. Furthermore, the improved fretting fatigue life from shot peening was explained by slower crack growth rates in the shallow surface layer with compressive residual stresses from shot peening. The successful life analyses hinged on three important issues: an accurate residual stress profile, a sufficiently small start crack and a valid crack growth model.

Place, publisher, year, edition, pages
2007. Vol. 30, no 10, 947-963 p.
Keyword [en]
fatigue crack growth, finite element method, fretting fatigue, peening, residual stress relaxation
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-6424DOI: 10.1111/j.1460-2695.2007.01165.xISI: 000249428500005Scopus ID: 2-s2.0-34548702218OAI: oai:DiVA.org:kth-6424DiVA: diva2:11129
Note
QC 20100827Available from: 2006-11-23 Created: 2006-11-23 Last updated: 2017-12-14Bibliographically 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.
Series
Trita-HFL. Report / Royal Institute of Technology, Solid mechanics, ISSN 1654-1472 ; 0423
Keyword
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
Identifiers
urn:nbn:se:kth:diva-4185 (URN)
Public defence
2006-12-06, F3, Lindstedtsvägen 28, KTH - Stockholm, 10:00
Opponent
Supervisors
Note

QC 20100827

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

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Alfredsson, Bo

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