Anomalies in Measurement of Residual Stress by X-Ray Diffraction

AbstractResidual stresses are expected to lead to a linear dependence of the interplanar spacing, d, on sin2ψ (where ψ is the sample tilt) and the stress can be obtained from the slope of this line, As a result of the linear dependence a two-tilt method is often employed to obtain the stress. However, when a specimen is subjected to extensive plastic deformation large deviations from a straight line can occur and a two-point method can lead to an erroneous stress determination. The results reported here show that: (1) this is more likely to occur in homogeneous materials than in multiphase materials (2) the oscillations follow closely the variation in peak intensity due to texture (3) the oscillations are caused by microstresses which are due to an "orientation" effect as suggested by Weidemann,A simple, easy-to-use procedure has been developed and tested to correct the data and obtain the correct macrostress.

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Interdiffusion in Co/Ta Multilayer Thin Films

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.237-240.554 ◽

2005 ◽

Vol 237-240 ◽

pp. 554-559 ◽

Cited By ~ 1

Author(s):

Hui Myeong Lee ◽

Byeong Seon Lee ◽

Chan Gyu Lee ◽

Yasunori Hayashi ◽

Bon Heun Koo

Keyword(s):

Structural Relaxation ◽

Multilayer Thin Films ◽

X Ray Diffraction ◽

Stress Release ◽

X Ray ◽

Angle Measurements ◽

Peak Intensity ◽

Straight Line ◽

Initial Stage ◽

Interdiffusion Coefficients

We will discuss the stress release phenomena, structural relaxation and interdiffusion processes during annealing. The [Co(4nm)/Ta(4nm)]38 multilayers were prepared by dc magnetron sputtering on Si substrate. The multilayers were annealed at various temperatures (523 - 673K) in vacuum (under 10-5 torr) furnace. The effective interdiffusion coefficients were determined from the slope of the best straight line fit of the first peak intensity versus annealing time [d ln(I(t)/I(0)) /dt] by X-ray diffraction (XRD) low angle measurements. The drastic decrease of the relative intensity in the initial stage shown due to the structural relaxation was excluded in the calculation of effective interdiffusion coefficients. The temperature dependence of interdiffusion in the range of 523 - 673K is described by D = 3.2×10-19 exp(-0.51±0.11 eV/kT) m2s-1.

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Determination of the Unstressed Lattice Parameter “a0” for (Triaxial) Residual Stress Determination by Xrays

Advances in X-ray Analysis ◽

10.1154/s0376030800014099 ◽

1984 ◽

Vol 28 ◽

pp. 281-288 ◽

Cited By ~ 2

Author(s):

Ismail Cevdet Noyan

Keyword(s):

Residual Stress ◽

Lattice Spacing ◽

Interplanar Spacing ◽

Lattice Parameter ◽

Shear Stresses ◽

Stress Determination ◽

Surface Layers ◽

X Ray ◽

D Values

Stress gradients in the direction of the surface normal influence the shape of the interplanar spacing “d” vs. sin2ψ (where ψ is the specimen tilt) plot obtained from the surface layers of a specimen.(1-3) If the gradients are caused by the shear stresses σ13, σ23, the “d” vs. sin2ψ plot exhibits “psi-splitting”, that is the “d” values measured at positive ψ tilts are different from the values measured at negative if tilts. (2) If the shear stresses σ13, σ23, are zero, but the normal stress σ33 exists in the layets penetrated by the x-ray beam, “d” vs. sin2ψ, plot exhibits curvature. (3) Various methods have been proposed to obtain the complete stress tensor from split or curved “d” vs. sin2ψ data, and all of these methods require the “unstressed” lattice spacing “d0” for their calculations.

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Review of Residual Stress Determination and Exploitation Techniques Using X-Ray Diffraction Method

Materials Science Forum ◽

10.4028/www.scientific.net/msf.524-525.229 ◽

2006 ◽

Vol 524-525 ◽

pp. 229-234

Author(s):

M. Belassel ◽

J. Pineault ◽

M.E. Brauss

Keyword(s):

Residual Stress ◽

Diffraction Method ◽

Point Of View ◽

Stress And Strain ◽

Stress Determination ◽

Calculation Methods ◽

X Ray Diffraction ◽

X Ray ◽

True Meaning ◽

The Difference

Although x-ray diffraction techniques have been applied to the measurement of residual stress in the industry for decades, some of the related details are still unclear to many production and mechanical testing engineers working in the field. This is because these details, specifically those associated with the transition between diffraction and mechanics, are not always emphasized in the literature. This paper will emphasize the appropriate calculation methods and the steps necessary to perform high quality residual stress measurements. Additionally, details are given regarding the difference between mechanical and x-ray elastic constants, as well as the true meaning of stress and strain from both diffraction and strain gage point of view. Cases where the material is subject to loading above the yield limit are also included.

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Determining Stresses in the Presence of Nonlinearities in Interplanar Spacing vs. Sin2ψ

Advances in X-ray Analysis ◽

10.1154/s037603080001702x ◽

1983 ◽

Vol 27 ◽

pp. 129-148 ◽

Cited By ~ 7

Author(s):

I. C. Noyan ◽

J. B. Cohen

Keyword(s):

Residual Stress ◽

Residual Stresses ◽

Interplanar Spacing ◽

Geometric Error ◽

Polycrystalline Materials ◽

X Ray ◽

Surface Residual Stresses ◽

Straight Line ◽

Annealed Powder ◽

Homogeneous Strain

AbstractThe physical meaning of non-linearities in “d” vs. sin2ψ lines, encountered in X-ray measurements of surface residual stresses in polycrystalline materials is investigated. It is shown that when oscillations are present in any one reflection, switching to another reflection to obtain a straight line in “d“ vs. sin2.ψ is feasible only under very special conditions. We also discuss the effect of “quasi-homogeneous” strain distributions and investigate the effects of ψ-range on the accuracy of X-ray residual stress measurements when ψ-splitting” is present. A new geometric error is also discussed that can not be detected by the “annealed powder” method often used for alignment.

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