Fretting fatigue of a NiCrMoV low pressure turbine shaft steel — the effect of different contact pad materials and of variable slip amplitude

Spink, G. M.

doi:10.1016/0043-1648(90)90152-z

Cited by 33 publications

(7 citation statements)

References 14 publications

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“…It has been reported that, if the tangential stress near the contact edge is higher, the surface damage would be more significant [17] and then a fretting crack easily nucleates [5]. The relative slip amplitude increases with increasing the pad rigidity, as shown in Fig.…”

Section: Effect Of Rigidity Of Contact Pad On Ff Strengthmentioning

confidence: 86%

“…The combination of vibratory load and centripetal force on the blade causes a fretting motion on the contact surfaces of the dovetail joint between the blade and the disc in turbine engines. Fretting acts as a stress concentrator and then a flaw generator that leads to premature crack nucleation, when compared with fatigue process without fretting contact [5]. One of the typical features of fretting fatigue is that crack nucleation and early crack propagation are significantly accelerated by fretting action [6].…”

Section: Introductionmentioning

confidence: 98%

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Effect of contact pad rigidity and fretting fatigue design curve

Mutoh

Jayaprakash

Asai

et al. 2010

Trans Indian Inst Met

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In fretting fatigue the nucleation and early propagation of fatigue crack depends on the state of stress near the contact edge. Contact pad rigidity is one of the factors that influence the stress state near the contact edge, there by influencing fretting fatigue strength. In the present study the effect of contact pad rigidity on fretting fatigue strength of turbine steels (Ni-Cr-Mo-V steel specimen with 12 Cr steel contact pads) were investigated. To study the effect of contact pad rigidity, contact pads with different pad foot height were used. FEA was performed to evaluate the stress distribution near the contact edge. The results showed that with increase in contact pad rigidity the fretting fatigue strength decreased. The results obtained were explained based on the stress distribution near the contact edge evaluated by using FEA. By combining the experimental results and FEA, fretting fatigue design curves were proposed. relationship between rigidity of contact pad and fretting fatigue strength is also clarified and then fretting fatigue design based on rigidity of contact pad can be developed. These design curves helps in real industrial applications to avoid FF failures.In the present study the effect of contact pad rigidity on fretting fatigue strength was investigated by using the contact pads with different foot height and contact length. Finite element analysis (FEA) was also performed to evaluate the stress distribution and the relative slip amplitude at the contact edge. From the results, it is confirmed that the contact pad rigidity influences the stress state at the contact edge (tangential stress and compressive stress) and then plays a dominant role in determining FF strength. Finally, by combining the experimental and FEA results fretting fatigue design curves were proposed, based on the dependence of FF life on both the tangential stress and compressive stress at the contact edge. Experimental procedure 2.1 MaterialThe material used in the present study was Ni-Cr-Mo-V steel, which was commonly used for steam turbine rotors. The contact pads were made of 12 Cr steel, which was commonly used for steam turbine blades. To study the effect of contact pad rigidity, contact pad with four different foot heights were used. The dimensions of the specimen and the contact pads are shown in Figs. 1 and 2, respectively. The chemical composition and mechanical properties of the specimen and the pad materials are shown in Table 1 and 2, respectively.

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Section: Effect Of Rigidity Of Contact Pad On Ff Strengthmentioning

confidence: 86%

Section: Introductionmentioning

confidence: 98%

Effect of contact pad rigidity and fretting fatigue design curve

Mutoh

Jayaprakash

Asai

et al. 2010

Trans Indian Inst Met

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“…Slip amplitude is important in terms of wear analysis and is also used directly in a fretting fatigue criterion. 6 Fretting wear damage has been found to increase with increasing slip amplitude, 7 and the strong effect of slip on fretting fatigue life has been reported. 8 The experimental measurement of slip has proven challenging.…”

Section: Introductionmentioning

confidence: 99%

A comparison of relative displacement fields between numerical predictions and experimental results in fretting contact

Juoksukangas

Lehtovaara

Mäntylä

2016

Proceedings of the Institution of Mechanical Engineers, Part J:

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In this paper, a comparison is made between calculated and measured displacements from a complete contact fretting test device. An experimental technique based on digital image correlation was used to measure the local displacement field at the contact interface. The material of the fretting specimen and pads was quenched and tempered steel. The effect of test device compliances and rigid body movement was minimized by measuring displacements very close to the contact interface. The measured displacements were successfully compared to the computed displacements of a corresponding finite element model. The relative slip amplitude in partial slip conditions, slip distribution across the contact, length of the slip region, and accumulated slip distribution, were compared. Relative slip decreases markedly with increasing normal load and friction coefficient. The friction coefficient was calibrated and determined as a function of loading cycles of fretting fatigue tests with two normal loads. The friction coefficient was found to increase at the beginning of tests and stabilize after about 1000 cycles, which is in agreement with general observations.

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“…1,2 The process of crack nucleation and initiation is critical in understanding fretting fatigue behaviour, since fretting fatigue crack generally remains hidden under the contacting bodies until it starts growing away from them, only then it can be monitored with ease. A number of researchers [3][4][5][6][7][8][9] have suggested that relative slip is a key factor, which dominates the crack nucleation and initiation process. Indeed, fretting fatigue crack nucleation life is crucial in high cycle fatigue loading situations experienced by blade-to-disk attachments in gas turbine engines 10,11 since it is a large portion of total fatigue life, that is, approximately 80-90% of total life.…”

Section: Introductionmentioning

confidence: 99%

“…Relative slip amplitude in fretting fatigue tests has been controlled by various techniques; normal contact load and bulk stress, 4 cumulative compliance of fretting test fixture, pad and specimen, 8 pad geometry. 7,9 These methods do not provide the relative slip amplitude as an independent control mode in a fretting fatigue test. To overcome this shortcoming, a dual actuator-based fretting test setup has been utilized in fretting fatigue studies.…”

Section: Introductionmentioning

confidence: 99%

Investigation into relative slip during fretting fatigue under partial slip contact condition

Sabelkin

Mall

2005

Fatigue Fract Eng Mat Struct

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A B S T R A C T A finite element analysis based methodology was developed to compute local relative slip on contact surface from the measured global relative slip away from contact surface. A set of springs was included in finite element model to simulate fretting fatigue test system. Compliance of springs was calibrated by comparing experimental and computed global relative slips. This methodology was then used to investigate local relative slip during fretting fatigue in cylinder-on-flat contact configuration under partial slip contact condition for unpeened and shot-peened titanium alloy, Ti-6Al-4V. Relative slip on contact surface is significantly smaller (about one order) than the measured global relative slip by using a conventional extensometer near the contact surface. Effects of coefficient of friction, rigidity of fretting fatigue system and applied stress to specimen on the global and local relative slips were characterized. Coefficient of friction and contact load have considerable effect on local relative slip, and practically no effect on global relative slip. Gross slip condition can develop at some locations on contact surface in spite of overall partial slip condition. Increase in rigidity of fretting fatigue system increases local relative slip but decreases global relative slip. Finally, fatigue life diagrams based on relative slip on contact surface are established for both unpeened and shot-peened titanium alloy. These show the same characteristics as of the conventional S-N diagram where fatigue life decreases with increase of relative slip. a = half width of contact zone E = Young's modulus E sp = modulus of elasticity of spring E pad = Young's modulus of pad F = applied force l AB = distance between contact point and location of extensometer's upper arm l DC = distance between points C and D M = bending moment acting on pad N = number of cycles N f = fatigue life P = normal contact load Correspondence: S. Mall.

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Fretting fatigue of a NiCrMoV low pressure turbine shaft steel — the effect of different contact pad materials and of variable slip amplitude

Cited by 33 publications

References 14 publications

Effect of contact pad rigidity and fretting fatigue design curve

Effect of contact pad rigidity and fretting fatigue design curve

A comparison of relative displacement fields between numerical predictions and experimental results in fretting contact

Investigation into relative slip during fretting fatigue under partial slip contact condition

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