Modeling of geometry effects in fretting fatigue

Bartha, Bence B.; Nicholas, T.; Farris, T. N.

doi:10.1016/j.triboint.2006.02.003

Cited by 13 publications

(11 citation statements)

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“…For simple geometries such as cylinder-on-flat contacts and assuming linear elastic material behavior and a constant COF, these responses can be determined analytically [22,23]. For more complex twodimensional contact configurations including flat with blending radii and surfaces with roughness, semi-analytical approaches can be used provided the material remains nearly linear elastic (e.g., [24]) or the finite element method is used when the geometry and loading representing the attachment is complex and when nonlinear material models need to be considered. The difficulty with using the finite element method is the need for extreme mesh refinement or submodeling at the fretting hot-spot location.…”

Section: Predicting Fretting Crack Formationmentioning

confidence: 99%

The Fretting Fatigue Behavior of Ti-6Al-4V

Neu

2008

KEM

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Abstract. This paper reviews the understanding of fretting fatigue with an emphasis on the behavior of Ti-6Al-4V. Advances in life prediction and assessment approaches are highlighted. The role of microstructure on fretting fatigue and its use to detect fretting fatigue damage can now be considered in assessment strategies. Various palliatives are used to enhance the fretting fatigue resistance. These include treatments to introduce compressive residual stress and surface coatings that reduce friction and/or protect the underlying structural material. IntroductionThis paper reviews the tremendous progress over the past decade to understand and predict the fretting fatigue behavior of Ti-6Al-4V, a common alloy used in applications requiring high specific strength. Fretting fatigue is of particular concern for dovetail attachments between the blades and disks in compressors of aerospace gas turbines, spline couplings of shafts, and mechanical joints in orthopedic implants. In the past decade there has been considerable focus on the fretting fatigue behavior of the duplex microstructure consisting of 60 vol. % equiaxed primary α (hcp structure) and 40 vol. % secondary lamellar α+β domains about 10 to 15 µm in size composed of alternating lathes of α and bcc-structured β. This was the baseline microstructure used for several projects carried out under the Air Force High Cycle Fatigue (HCF) program from 1995 to 2005 [1,2]. Unless noted otherwise, the majority of the data reported in this review was generated on this or similar microstructure. The microstructure has an initial random texture with yield strength 930 MPa, ultimate tensile strength 978 MPa, and cyclic yield strength of 797 MPa [1].The fretting fatigue process can be divided into two parts. The first is the formation of fretting cracks and the second is the growth of fretting fatigue cracks. The drivers for each of these processes are different. Both processes must occur to realize a catastrophic fretting fatigue failure. If fretting cracks do not form, fretting fatigue will not occur. But even if fretting cracks form, a catastrophic fretting fatigue failure will not occur if these cracks do not grow outside of the fretting fatigue process volume (FFPV) associated with the formation of the crack. Hence, the fretting fatigue limit is associated with the threshold limit for propagating the fretting cracks. In most fretting fatigue experiments and in applications, the drivers for fretting crack formation and crack growth outside of the FFPV cannot be easily separated, so there is an apparent coupling between the two. However, experiments involving the independent control of the drivers for fretting crack formation and crack growth (e.g., [3,4]) suggest that these two processes can be separated for the purposes of material response and prediction analyses. This is extremely helpful in understanding how different palliatives mitigate the fretting drivers. Some palliatives are aimed at fretting crack formation while others at reducing the fretting fatigue crack...

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Section: Predicting Fretting Crack Formationmentioning

confidence: 99%

The Fretting Fatigue Behavior of Ti-6Al-4V

Neu

2008

KEM

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“…The second system, called "fixture B", uses a flat dogbone specimen contacted on both sides with cylindrical or short flat pads with blending radii at the edges of contact, as shown in Fig. 2 [6]. This fixture is typical of many reported in the literature [7].…”

Section: Fretting Fixturesmentioning

confidence: 99%

“…The experimental results for this work have been previously documented [4,6,9]. Conditions (shown in Table 1) were selected from available data to facilitate comparison of the experimental results and analysis that was performed using those conditions.…”

Section: Experiments and Analysismentioning

confidence: 99%

“…The inputs to CAPRI were the pad geometry; the total normal force, P; and tangential force, Q; bulk stress, σ bulk ; and material properties including Young's modulus, E; Poisson's ratio, ν; and coefficient of friction, μ. The subsurface stresses were calculated using Fast Fourier Transform (FFT) techniques that accounted for the effect of specimen thickness on the stress gradient [6]. Additional details of this work including the study of the influence of size and thickness can be found in Bartha [13].…”

Section: Experiments and Analysismentioning

confidence: 99%

“…The subsurface stresses were calculated using Fast Fourier Transform (FFT) techniques that accounted for the effect of specimen thickness on the stress gradient [6]. Additional details of this work including the study of the influence of size and thickness can be found in Bartha [13]. The surface and subsurface stress fields were then used to correlate with S-N and fracture mechanics models respectively.…”

Section: Experiments and Analysismentioning

confidence: 99%

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Fatigue Loading and Life Prediction in Three Fretting Fatigue Fixtures

et al. 2008

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Three fixtures for conducting laboratory fretting fatigue tests are described and their respective testing methods and the results of the analysis are compared. Each of these fixtures has been used to investigate the effects of various parameters of interest in fretting fatigue. These fixtures include a unique apparatus in which all load applied to the specimen is transferred to the fretting pads, an apparatus similar to many found in the literature where partial load transfer occurs across the pads, and a simplified dovetail fixture in which the clamping load, P, and the shear load, Q, are varied in phase. Select test conditions from prior experiments performed on identical material and resulting in similar lives ranging from one to ten million cycles from these fixtures are identified. The various testing conditions were used to compute the unique stress field for each case. The resulting contact stresses were used to calculate crack initiation based criteria, and to calculate stress intensity factors. The three fixtures were shown to be able to accommodate a range of loads, fretting pad contours, and specimen geometries that produced a variety of stress fields. A crack-initiation-based criterion was shown to predict the failure lives of thinner specimens accurately. The stress intensity factor calculations showed the possibility of a crack arresting for a stress field that decays rapidly and the possibility of a local minimum for K as a function of depth. The fixtures are shown to be complementary in generating data for development of robust fretting fatigue models that use these criteria.

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