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Effect of Peak Positioning Method on Accuracy of X-Ray Diffraction Residual Stress Measurement



In this paper, five peak positioning methods and their effects on the accuracy of X-ray diffraction (XRD) residual stress measurement are considered. Also the effects of various parameters such as absorption coefficient, Lorentz-polarization factor, background correction and Kα2 stripping are evaluated on the precision of different methods. For this aim, the residual stress of a multilayer Al/Cu cold rolled plate is measured by the XRD method. These five peak positioning methods are: maximum intensity method (Imax method), middle position of the width at half maximum intensity method (MPHM method), Gaussian peak profile function method, parabola method, and center of gravity (C.o.G) method. It is shown that not only the results of all methods are not same, but also all of them have different behaviors and responses in respect to the mentioned parameters. Among the mentioned parameters, Kα2 striping and background correction are the most effective parameters in results of all peak positioning methods. It is also shown that the C.o.G. method has the lowest standard deviation, leading to the high linearly d-spacing versus sin2ψ diagram for the residual stress measurements of the samples. Moreover, it is concluded that higher R2 value does not necessarily indicate a more accurate method.