Precision and accuracy of stress measurement with a portable X-ray machine using an area detector
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- 作者：Seung-Yub Lee ; Jinjing Ling ; Shenghe Wang and Joaquin Ramirez-Rico
- 关键词：X-ray diffraction ; stress measurement ; area detectors ; portable X-ray devices
- 刊名：Journal of Applied Crystallography
- 出版年：2017
- 出版时间：February 2017
- 年：2017
- 卷：50
- 期：1
- 页码：131-144
- 全文大小：1974K
- ISSN：1600-5767
文摘
The use of portable X-ray stress analyzers, which utilize an area detector along with the newly adopted `cosα' or full-ring fitting method, has recently attracted increasing interest. In laboratory conditions, these measurements are fast, convenient and precise because they employ a single-exposure technique that does not require sample rotation. In addition, the effects of grain size and orientation can be evaluated from the Debye ring recorded on the area detector prior to data analysis. The accuracy of the measured stress, however, has been questioned because in most cases just a single reflection is analyzed and the sample-to-detector distances are relatively short. This article presents a comprehensive analysis of the uncertainty associated with a state-of-the-art commercial portable X-ray device. Annealed ferrite reference powders were used to quantify the instrument precision, and the accuracy of the stress measurement was tested by in situ tensile loading on 1018 carbon steel and 6061 aluminium alloy bar samples. The results show that the precision and accuracy are sensitive to the instrument (or sample) tilt angle (ψ0) as well as to the selected hkl reflection of the sample. The instrument, sample and data analysis methods all affect the overall uncertainty, and each contribution is described for this specific portable X-ray system. Finally, on the basis of the conclusions reached, desirable measurement/analysis protocols for accurate stress assessments are also presented.