Considerations for Collecting Reliable Xrd Residual Stress Data across the Full 2theta Range

The applicability of residual stress analysis is expanded to the full 2theta range, particularly to lower diffraction angles (2θ<<120), in order to be able to analyze residual stress in complex samples. For reliable results it is crucial that systematic errors are absent. The systematic errors considered in this paper are alignment errors like specimen displacement and incident beam misalignment. Verification measurements on a stress-free sample are required in combination with a suitable test criterion. A search in the standardization literature leads to three different criteria, which are compared with each other. From these three criteria only the Euronorm criterion appears to be generally applicable and is selected for further evaluation. Various experiments are performed to test different setups for their applicability at low diffraction angles. These experiments and the use of the Euronorm criterion lead to recommendations with respect to the applicable angular range. Only high diffraction angles (above 120) should be applied in case of the focusing optics geometry. Much lower angles (above 60-70) can be used when software corrections for alignment errors are applied in combination with the focusing optics geometry. The lowest angles (above 30-40) can be used with the parallel beam geometry.