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Assessing the Validity of Diffraction Stress Data with the Goodness-Of-Fit Statistic

Published online by Cambridge University Press:  06 March 2019

Thomas A. Lohkamp  and
R. A. Winhoitz
Thomas A. Lohkamp
Affiliation:
Research Reactor Center and Mechanical & Aerospace Engineering University of Missouri-Columbia
R. A. Winhoitz
Affiliation:
Research Reactor Center and Mechanical & Aerospace Engineering University of Missouri-Columbia
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According to the standard model, strain in polycrystalline materials transforms like a tensor when measured with diffraction in different directions. This model predicts linear variation of d-spacing with sin2ѱ if the stresses σ13 and σ23 are absent or predicts ѱ-splitting if they are present. In diffraction stress measurements, d vs. sin2ѱ plots often exhibit behavior that cannot be predicted from this model. When such discrepancies are observed, stresses calculated from the data will not always be valid. Current practice is to determine the validity of data by visually inspecting d vs. sin2ѱ plots and subjectively assessing the goodness-of-fit. This paper proposes the χ2 statistic as a tool for quantitatively determining goodness-of-fit, and it presents experimental results from the application of the statistic.

Type
Research Article
Information
Advances in X-Ray Analysis , Volume 39: Forty-Fourth Annual Conference on Applications of X-ray Analysis, July 31 - August 4, 1995 , 1995 , pp. 281 - 289
Copyright
Copyright © International Centre for Diffraction Data 1995

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