Effects of microstructure on fretting fatigue crack initiation behavior of Ti-6Al-4V

Mall, S.; Namjoshi, S. A.; Porter, W.J.

doi:10.1016/j.msea.2004.05.019

Cited by 40 publications

(11 citation statements)

References 24 publications

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“…This trend is consistent with fretting crack nucleation predictions that employ microstructure-based modeling [74]. In another study a homogeneous bi-modal microstructure (i.e., the duplex microstructure) was shown to have better fretting fatigue crack nucleation resistance than a heterogeneous lamellar microstructure [75]. This is consistent with plain fatigue trends for crack nucleation and is opposite the long crack growth behavior where a heterogeneous lamellar microstructure tends to provide more resistance to crack growth due to the increased torturous nature of the crack path [76].…”

Section: Effect Of Microstructuresupporting

confidence: 82%

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: Effect Of Microstructuresupporting

confidence: 82%

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

Neu

2008

KEM

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“…The HCF behaviour of the material is dependent on the crack nucleation and growth time. In particular, as demonstrated by Mall et al [67], crack initiation resistance in Ti-6Al-4V is increased with finer and more homogenous microstructures. Fatigue cracks typically nucleate due to irreversible slip in the longest crystallographic slip bands in the microstructure [57].…”

Section: Micro-mechanism Contributionmentioning

confidence: 75%

A Review of the As-Built SLM Ti-6Al-4V Mechanical Properties towards Achieving Fatigue Resistant Designs

Agius

Kourousis

Wallbrink

2018

Metals

155

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Ti-6Al-4V has been widely used in both the biomedical and aerospace industry, due to its high strength, corrosion resistance, high fracture toughness and light weight. Additive manufacturing (AM) is an attractive method of Ti-6Al-4V parts' fabrication, as it provides a low waste alternative for complex geometries. With continued progress being made in SLM technology, the influence of build layers, grain boundaries and defects can be combined to improve further the design process and allow the fabrication of components with improved static and fatigue strength in critical loading directions. To initiate this possibility, the mechanical properties, including monotonic, low and high cycle fatigue and fracture mechanical behaviour, of machined as-built SLM Ti-6Al-4V, have been critically reviewed in order to inform the research community. The corresponding crystallographic phases, defects and layer orientations have been analysed to determine the influence of these features on the mechanical behaviour. This review paper intends to enhance our understanding of how these features can be manipulated and utilised to improve the fatigue resistance of components fabricated from Ti-6Al-4V using the SLM technology.

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“…In addition, this reduction in the crack growth rate was explained by a microstructure-dependent mode of crack growth that involved crystallographic bifurcation (i.e., the larger grain size permits larger bifurcation and thereby decreases crack growth rate). [28] V. CONCLUSIONS…”

Section: Crack Propagationmentioning

confidence: 97%