Surface residual stresses, surface topography and the fatigue behavior of Ti-6AI-4V

Leverant, G. R.; Langer, B.S.; Yuen, A.; Hopkins, Sharla

doi:10.1007/bf02817635

Cited by 65 publications

(25 citation statements)

References 7 publications

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“…In particular, this process cannot be expected to prevent dislocation movement in the surface layer of coated parts by either a local increase of the yield strength in the outer surface (mechanical hardening) or by introducing favorable compressive residual stresses. On the contrary, these effects are typically induced onto substrates processed by mechanical treatments, such as shot peening, even if they often concurrently cause a deterioration in aesthetic aspect and the finishing of exposed surface, as well as causing several problems connected with setting the most appropriate operating parameters, not to mention high plant, operating, and running costs [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Al2O3 thin coating of AA 6082 T6 components using a fast regime fluidized bed

2006

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Fluidized bed processing is a relatively novel method for coating metal substrates. A detailed study was carried out into surface property and in micro-structure changes induced by fluidized bed processing. In particular, fluidized bed processing of AA 6082 T6 aluminum alloy components using alumina Al 2 O 3 powder was investigated. Firstly, the build up of Al 2 O 3 films was studied and characterized in terms of coating thickness and adhesion. It was found that trends of deposited Al 2 O 3 were consistent with fluidized bed processing time. Secondly, the effect of fluidized bed treatment on surface properties of processed components was examined. Surface morphology was significantly affected and its evolution according to processing time was accounted for. Both compressive residual stresses and increased dislocation density were induced by treatment of external layers of samples, and significant hardening was also detected. Lastly, the ability of fluidized bed processing was tested on Fad hoc' fatigue samples. Rupture of fluidized bed treated samples as well as untreated samples was also discussed. At any rate, the fatigue behavior of processed components significantly improved. This quite new and unprecedented result is ascribed to the compressive residual stresses and work hardening induced by FB treatment in the outermost surface layers of the aluminum alloy. D

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Section: Introductionmentioning

confidence: 99%

Al2O3 thin coating of AA 6082 T6 components using a fast regime fluidized bed

2006

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“…Increasing relaxation with higher temperature has been demonstrated by Potter and Millard (1977) in 7075-T6 aluminum alloy without cycling and by Leverant et al (1978) in Ti-6A1-4V subjected to bending.…”

Section: Residual Stresses In Fatiguementioning

confidence: 98%

“…To demonstrate the influence of the latter quantity Esquivel and Evans (1968) has shown that the degree of relaxation increases with increasing stress gradient in shot peened 4130 steel and both Esquivel and Evans (1968) and Hayashi and Doi (1971) have found that the greatest relaxation takes place on the surface. Leverant et al (1978) have shown that not only is the strain amplitude important, but also cycling awout a mean strain significantly affects the relaxation. A mean strain of -.3 percent was found to induce greater relaxation in shot peened Ti-6AI-4V than a mean strain of +.3 percent.…”

Section: Residual Stresses In Fatiguementioning

confidence: 99%

“…The relaxation rate is most rapid in the early part of fatigue life (Morrow et al, 1960;Koves, 1965;Esquivel, 1968;Ericsson et al, 1971;Seppi, 1976;and Leverant et al, 1978). Quantitative relations based on a linear proportionality between residual stress and the logarithm of the number of cycles have been empirically established (Kodama, 1971(Kodama, , 1972Potter and coworkers, 1972;Wohlfahrt, 1973;Radhakrishnan and Prasad,1976).…”

Section: Residual Stresses In Fatiguementioning

confidence: 99%

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The Measurement of Residual Stresses by X-Ray Diffraction Techniques

James¹,

Cohen²

1978

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“…The latter being a more influential factor in notch fatigue [2,23] than smooth fatigue. The SP-induced surface roughness, which has also been given an important consideration in several studies [7,8,26], can have a competing influence on the positive effects of the compressive stress and the cold work level, especially under thermal-mechanical conditions where the RS profile may significantly relax.…”

Section: Introductionmentioning

confidence: 99%

Nominal Versus Local Shot-Peening Effects on Fatigue Lifetime in Ti-6Al-2Sn-4Zr-6Mo at Elevated Temperature (Preprint)

Jha¹,

John²,

Larsen³

2008

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The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Services, Directorate for Information AFRL-RX-WP-TP-2008-4342 DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release; distribution unlimited. SUPPLEMENTARY NOTESPAO case number 88ABW-2008-0104, cleared 09 September 2008. This is a work of the U.S. Government and is not subject to copyright protection in the United States. Paper contains color. ABSTRACTA study of the elevated temperature fatigue lifetime variability in the shot-peened condition of the a+b titanium alloy, -Ti-6Al-2Sn-4Zr-6Mo, is presented. It is shown that failures separate into two distributions: (i) governed by the nominal residual stress profile, promoting subsurface crack initiation and longer lifetimes, and (ii) the life-limiting behavior that is controlled by localized material-shot-peening interaction. In the residual-stress-free condition, failures occurred predominantly by surface crack initiation at the microstructural scale, on the order of 10 um, by crystallographic facet formation in one of a few a particles and/or colonies. This mechanism was mitigated under the nominal shot-peening residual stress profile, producing failures initiating from the subsurface region by crystallographic faceting spread over a significantly larger area (equivalent diameter of about 100-200 um) thank in the absence of residual stress. SUBJECT TERMSFatigue variability, lifetime distribution, shot-peening, residual stress, Ti-6Al-2Sn-4Zr-6Mo AbstractA study of the elevated temperature (260°C) fatigue lifetime variability in the shot-peened condition of the α+β titanium alloy, Ti-6Al-2Sn-4Zr-6Mo, is presented. It is shown that failures separate into two distributions: (i) governed by the nominal residual stress profile, promoting subsurface crack initiation and longer lifetimes, and (ii) the life-limiting behavior that is controlled by localized material -shot-peening interaction. In the residual-stress-free condition, failures occurred predominantly by surface crack initiation at the microstructural scale, on the order of 10 μm, by crystallographic facet formation in one or a few α particles and/or colonies.This mechanism was mitigated under the nominal shot-peening residual stress profile, producing failures initiating from the subsurface region by crystallographic faceting spread over a significantly larger area (equivalent diameter of about 100-200 μm) than in the absence of residual stress. Although the microstructure-scale surface crack-initiation was suppressed, the life-limiting failures under shot-peening continued to occur by ...

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Surface residual stresses, surface topography and the fatigue behavior of Ti-6AI-4V

Cited by 65 publications

References 7 publications

Al2O3 thin coating of AA 6082 T6 components using a fast regime fluidized bed

Al2O3 thin coating of AA 6082 T6 components using a fast regime fluidized bed

The Measurement of Residual Stresses by X-Ray Diffraction Techniques

Nominal Versus Local Shot-Peening Effects on Fatigue Lifetime in Ti-6Al-2Sn-4Zr-6Mo at Elevated Temperature (Preprint)

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