Thermomechanical relaxation of residual stress in shot peened nickel base superalloy

Cao, Weicheng; Khadhraoui, M.; Brenier, B.; Guédou, Jean-Yves; Castex, L.

doi:10.1179/026708394790163546

Cited by 9 publications

(17 citation statements)

References 1 publication

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“…Numerical models to predict these initial residual stress profiles have been developed 16,17 but are much less common than experimental measurements. Tufft 18 has proposed a simple functional form that she claims can empirically describe the initial profile of SP residual stresses for many materials, if experimental data are available to which the equation can be fitted.…”

Section: Peening and Related Surface Treatmentsmentioning

confidence: 99%

A literature survey on the stability and significance of residual stresses during fatigue

McClung

2007

Fatigue Fract Eng Mat Struct

303

181

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A B S T R A C T Many manufacturing processes can induce residual stresses in components. These residual stresses influence the mean stress during cyclic loading and so can influence the fatigue life. However, the initial residual stresses induced during manufacturing may not remain stable during the fatigue life. This paper provides a broad and extensive literature survey addressing the stability of surface and near-surface residual stress fields during fatigue, including redistribution and relaxation due to static mechanical load, repeated cyclic loads, thermal exposure and crack extension. The implications of the initial and evolving residual stress state for fatigue behaviour and life prediction are addressed, with special attention to fatigue crack growth. This survey is not a critical analysis; no detailed attempt is made to evaluate the relative merits of the different explanations and models proposed, to propose new explanations or models or to provide quantitative conclusions. Primary attention is given to the residual stresses resulting from four major classes of manufacturing operations: shot peening and related surface treatments, cold expansion of holes, welding and machining. A = function of material and temperature C = empirical constant CX = cold expansion DOD = Department of Defence DR = deep rolling EP = electropolished FAA = Federal Aviation Administration FCG = fatigue crack growth FE = finite element FTI = Fatigue Technology, Inc. GBP = glass bead peening GP = gravity peening JSSG = Joint Service Specification Guide k = Boltzmann's constant LBP = low plasticity burnishing LCF = low-cycle fatigue LSP = laser shock peening m = empirical constant Correspondence: R. C. McClung. Fatigue Fract Engng Mater Struct 30, 173-205 173 174 R. C. McCLUNG Q = effective activation energy for residual stress relaxation R = stress ratio S-N = Stress-Life SP = shot peening SR = stress relieved t = time T = Temperature USAF = United States Air Force WP = water peening σ RS = residual stress 3D = three-dimensional

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Section: Peening and Related Surface Treatmentsmentioning

confidence: 99%

A literature survey on the stability and significance of residual stresses during fatigue

McClung

2007

Fatigue Fract Eng Mat Struct

303

181

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“…The stored energy is proportional to local variations in the lattice distortion, which can be observed using diffraction methods by studying the extent of peak broadening. Cao et al [12] described the process of thermal relaxation as a microplastic deformation, by which elastic strains are converted into plastic ones. In effect, the eigenstrain, i.e., the misfit between the stress-free shapes of the surface layers and the bulk caused by the peening process, is relaxed by short-and long-range diffusion phenomena (mobility of defects and dislocations).…”

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confidence: 99%

“…Cao et al [12] studied the relaxation of stress under isothermal fatigue for shot-peened ASTROLOY plates, subjected to different numbers of stress-controlled cycles (below the macroscopic yield limit, with R ϭ 0) at 650 °C. Building on the work by Kodama, [15] they identified two distinct stages for the relaxation.…”

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confidence: 99%

“…This process may be accelerated in regions of high stored energy and can take place by the annihilation or rearrangement of thermally mobile defects (vacancies and dislocations) present in the work-hardened surface region. [12] The annihilation gives rise to the reduction of the stored energy of the lattice. The stored energy is proportional to local variations in the lattice distortion, which can be observed using diffraction methods by studying the extent of peak broadening.…”

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confidence: 99%

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Stress relaxation of shot-peened UDIMET 720Li under solely elevated-temperature exposure and under isothermal fatigue

Kim

Evans

Shackleton

et al. 2005

Metall Mater Trans A

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The aim of this experimental study was to quantify the changes that occur to the residual-stress state and the near-surface work-hardened zone as a function of depth in a shot-peened UDIMET 720Li Ni superalloy following solely thermal exposure and in combination with strain-controlled fatigue loading at two strain amplitudes. Residual-stress measurements were performed using the sin 2 method on a laboratory X-ray diffractometer as a function of depth by successive electrochemical removal of material. It was found that the as-peened variation in diffraction-peak width (X-ray) with depth correlated well with the recorded hardness profile. A hardness increase in excess of 50 pct was recorded close to the surface. Regarding solely thermal exposure, it was found that the near-surface compressive stresses were relieved to some extent at all temperatures (350 °C to 725 °C) after short-term exposure, being reduced by up to 50 pct at the highest temperatures (650 °C to 725 °C). The isothermally fatigued samples strained at 0.6 pct amplitude displayed similar stress-relaxation behavior to the thermally loaded samples, indicating that at such small strains, stress relaxation is controlled predominantly by thermal relaxation processes. In contrast, stress relaxation following strain-controlled fatigue at 1.2 pct strain is governed by a combination of thermal and mechanical processes. The mechanically induced relaxation component is anisotropic, being significantly greater along the loading axis than transverse to it. Unsurprisingly, with increasing temperature, the thermal contribution to stress relaxation becomes increasingly important and the degree of in-plane anisotropy of stress relaxation lessens.

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“…In the whole study, residual stresses were normalized by the intrinsic fatigue strength of the studied material. These results were compared with the results of the shot‐peening software that has been developed by the MécaSurf Laboratory 4 , 7 . This analytical model is based on a Zarka structure analysis method and a four‐parameter elastoplastic constitutive equation 8 .…”

Section: Investigated Material Treatments and Structuresmentioning

confidence: 99%

Cyclic modelling of the mechanical state produced by shot‐peening

Lillamand

Barrallier

Lalanne³

et al. 2001

Fatigue Fract Eng Mat Struct

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During low cycle fatigue of shot‐peened parts, the competition between the compressive residual stresses and the hardening damage, both of which are produced by cumulated plastic strains, is of major importance for lifetime improvement. In order to take into account these effects in life prediction, the shot‐peening treatment must be considered as a first step in the service life of the studied part. The predicted residual stresses provided by the existing shot‐peening models are not sufficient when taking account of the induced mechanical state. The proposed methodology in this paper describes the shot‐peening process by a new cyclic approach where the Chaboche constitutive equations, commonly used in the aircraft industry, show the best promise. A reversed method is employed to quantify, after shot‐peening, the complete mechanical state in line with commonly used life‐prediction algorithms. Computations are carried out for a shot‐peened TiAl6V4 titanium alloy as used in the low pressure stage compressor of turbo‐engine discs.

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Thermomechanical relaxation of residual stress in shot peened nickel base superalloy

Cited by 9 publications

References 1 publication

A literature survey on the stability and significance of residual stresses during fatigue

A literature survey on the stability and significance of residual stresses during fatigue

Stress relaxation of shot-peened UDIMET 720Li under solely elevated-temperature exposure and under isothermal fatigue

Cyclic modelling of the mechanical state produced by shot‐peening

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