Precision and accuracy of stress measurement with a portable X-ray machine using an area detector

Abstract

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

Intermethod Comparison and Evaluation of Measured Near Surface Residual Stress in Milled Aluminum

“…The incompleteness of the rings in Fig. 17 is consistent with material texture and preferred grain orientation [23], which is typical of rolled aluminum plate. The Debye rings were generally less uniform for σ yy (Fig.…”

Railway Vehicle Wheel Restoration by Submerged Arc Welding and Its Characterization

“…This method captures diffracted X-ray beam by a 2 dimensional detector, so measurement is faster and more convenient than the traditional sin 2 ψ method, which detects diffracted X-ray beam by line detectors. Delbergue et al [16] and Lee et al [17] showed that the cos α method provides a better measurement repeatability than the sin 2 ψ method. Figure 10 and Table 4 show the measuring points and measured residual stresses, σ x and σ y .…”

Railway Vehicle Wheel Restoration by Submerged Arc Welding and Its Characterization

“…This method captures diffracted X-ray beam by a 2 dimensional detector, so measurement is faster and more convenient than the traditional sin 2 ψ method, which detects diffracted X-ray beam by line detectors. Delbergue et al [16] and Lee et al [17] showed that the cos α method provides a better measurement repeatability than the sin 2 ψ method. Figure 10 and Table 4 show the measuring points and measured residual stresses, σx and σy.…”