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Profile Fitting in Residual Stress Determination

Published online by Cambridge University Press:  06 March 2019

T. J. Devine  and
J. B. Cohen
T. J. Devine
Affiliation:
Department of Materials Science and Engineering The Technological Institute Northwestern University Evanston, IL 60201
J. B. Cohen
Affiliation:
Department of Materials Science and Engineering The Technological Institute Northwestern University Evanston, IL 60201
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Extract

Of major importance in the determination of residual stress via diffraction is the accuracy of the measurement of the scattering angle (2 θp) of a Bragg peak. This determines the accuracy of the interplanar (d) spacing and hence the strain and stress. In the U.S., the most commonly accepted method of determining peak position is a parabolic fit near the top of a peak. (While a diffraction peak is not parabolic, this is a satisfactory function near the maximum.) The error in this procedure has been derived and tested, and it has been shown that a multipoint fit with a least 7 points is rapid and as precise or more precise than the centroid, the bisector of the half width, or cross correlation, except for sharp peaks in which case the centroid or cross correlation are slightly better. Thus a parabolic fit is generally useful and, since a least-squares fit to this function is readily carried out on modem micro-processors, automatical of a stress measurement is possible, including evaluation of errors.

Type
Research Article
Information
Advances in X-Ray Analysis , Volume 29: Thirty-Fourth Annual Conference on Applications of X-ray Analysis, August 5-9, 1985 , 1985 , pp. 89 - 101
Copyright
Copyright © International Centre for Diffraction Data 1985

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