Normal load effects in fretting fatigue of titanium and aluminum alloys

Fretting-wear and fretting-fatigue loadings can both result in wear (material loss) and in crack nucleation and propagation (fatigue process). This paper deals with cracking induced by small amplitude displacements in the case of aeronautic aluminium alloys. The two sets of fretting maps are introduced: running condition fretting map is composed of partial slip (sticking), mixed fretting and gross sliding regime; material response fretting map is associated with two macro-degradation modes. Crack nucleation and propagation are analysed for every fretting regime. The mixed fretting regime appeared most detrimental with regards to fatigue cracking. Slip amplitude and normal load main effects discussed for fretting wear can be used to justify the fatigue limit decrease often obtained for fretting fatigue experiments.

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Fretting Fatigue Design of Subsea Connectors: A Generalised Approach to Testing

Volume 2A: Structures, Safety, and Reliability ◽

10.1115/omae2020-18608 ◽

2020 ◽

Author(s):

H. Andresen ◽

D. A. Hills ◽

Anders Wormsen ◽

K. A. Macdonald

Keyword(s):

Crack Nucleation ◽

Normal Load ◽

Asymptotic Methods ◽

Fretting Fatigue ◽

Test Design ◽

Frictional Contacts ◽

Fatigue Design ◽

Geometrical Features ◽

Fatigue Data ◽

Constant Normal Load

Abstract In this paper fretting fatigue is addressed as a potential design consideration for wellhead connectors. The study of near-edge relative motion for frictional contacts under constant normal load is described using analytical, numerical and asymptotic methods. Based on published fretting fatigue experimental data an argument is drawn for a generalised fretting fatigue test design. We do this by reducing the parameters responsible for crack nucleation to the smallest number possible and thereby revealing the fretting fatigue strength as a material property independent of geometrical features. Easy to apply recipes are described and thoughts on a potential apparatus are shared with the reader. Commercial potential lies in the wide-ranging applicability of experimental results across many prototypes and loadings once an appropriate amount of fretting fatigue data has been generated for the material in question.

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System Wear Life Estimation Under Uncertainty

Volume 13: Design, Reliability, Safety, and Risk ◽

10.1115/imece2018-87015 ◽

2018 ◽

Author(s):

Mohammad Pourmostafaei ◽

Mohammad Pourgol-Mohammad ◽

Mojtaba Yazdani ◽

Hossein Salimi

Keyword(s):

Experimental Data ◽

Sliding Wear ◽

Normal Load ◽

Material Loss ◽

Life Estimation ◽

Wear Life ◽

Pin On Disc ◽

Load Effects ◽

Sliding Distance ◽

Degradation Evaluation

In this paper, a new model is proposed for system degradation evaluation under sliding wear failure mechanism. This model estimates the material loss by progression of sliding distance. This model is generated by considering physical and geometrical aspects of system under wear mechanism. Several sets of experimental data are used for validation of the presented model. These experimental data are related to pin-on-disc test of Tungsten Carbide pins. These sets of data include initially conformal and non-conformal contacts. One set of data of pin-on-disc test by ASTM-G99 standard is used for additional validation of the model and for investigation of normal load effects on the parameters of presented model. Finally, uncertainty analysis is done by Monte-Carlo simulation to determine the variations of the predicted wear caused material loss.

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Analyses of Contact Pressure and Stress Amplitude Effects on Fretting Fatigue Life

Journal of Engineering Materials and Technology ◽

10.1115/1.1288211 ◽

2000 ◽

Vol 123 (1) ◽

pp. 85-93 ◽

Cited By ~ 44

Author(s):

K. Iyer ◽

S. Mall

Keyword(s):

Finite Element ◽

Fatigue Life ◽

Contact Pressure ◽

Stress Amplitude ◽

Normal Load ◽

Contact Region ◽

Local Stress ◽

Fretting Fatigue ◽

Element Analysis ◽

Stress Ratios

Elastic-plastic finite element analyses of a cylinder-on-plate configuration, studied experimentally, were performed to provide an explanation for the decrease in fretting fatigue life with increasing contact pressure. Three values of normal load, namely 1338 N, 2230 N, and 3567 N, and three stress ratios (0.1, 0.5, and 0.7) were considered. Based on a previously determined dependency between contact pressure and friction coefficient, the effect of coefficient of friction was also evaluated. The deformation remained elastic under all conditions examined. Cyclic, interfacial stresses, and slips were analyzed in detail. The amplification of remotely applied cyclic stress in the contact region is shown to provide a rationale for the effect of contact pressure and stress amplitude on life. Comparisons with previous experiments indicate that the local stress range computed from finite element analysis may be sufficient for predicting fretting fatigue life. Further, the results suggest that the slip amplitude and shear traction may be neglected for this purpose.

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Fretting-Fatigue Analysis of Shot-Peened Al 7075-T651 Test Specimens

Metals ◽

10.3390/met9050586 ◽

2019 ◽

Vol 9 (5) ◽

pp. 586 ◽

Cited By ~ 2

Author(s):

Vicente Martín ◽

Jesús Vázquez ◽

Carlos Navarro ◽

Jaime Domínguez

Keyword(s):

Fatigue Life ◽

Residual Stresses ◽

Shot Peening ◽

Normal Load ◽

Fretting Fatigue ◽

Fatigue Tests ◽

Material Surface ◽

Tangential Load ◽

Bulk Stress ◽

Al 7075

Shot peening is a mechanical treatment that induces several changes in the material: surface roughness, increased hardness close to the surface, and, the most important, compressive residual stresses. This paper analyzes the effect of this treatment on alloy Al 7075-T651 in the case of fretting fatigue with cylindrical contact through the results of 114 fretting fatigue tests. There are three independent loads applied in this type of test: a constant normal load N, pressing the contact pad against the specimen; a cyclic bulk stress σ in the specimen; and a cyclic tangential load Q through the contact. Four specimens at each of 23 different combinations of these three parameters were tested—two specimens without any treatment and two treated with shot peening. The fatigue lives, contact surface, fracture surface, and residual stresses and hardness were studied. Improvement in fatigue life ranged from 3 to 22, depending on fatigue life. The relaxation of residual-stress distribution related to the number of applied cycles was also measured. Finally, another group of specimens treated with shot peening was polished and tested, obtaining similar lives as in the tests with specimens that were shot-peened but not polished.

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