New Approach for Fast Residual Strain Estimation Through Rational 2D Diffraction Pattern Processing

Highly brilliant synchrotron X-ray beams enable fast non-destructive evaluation of residual strains even in large and thick engineering objects under operando conditions. Large datasets of 2D patterns are acquired at high rate, meaning that near real time evaluation demands fast data processing and mapping of residual strain. The somewhat time-consuming traditional data processing algorithms involve the conversion of each 2D X-ray diffraction pattern within a substantial stack to 1D intensity plots by radial-azimuth sectoral binning (“caking”), followed by peak fitting to determine peak center positions. A new approach was realized and programmed as the open-source code to perform residual strain evaluation by direct ‘polar transformation’ of 2D X-ray diffraction patterns. We compare residual strain calculations by ‘polar transformation’ and ‘caking’ respectively for an Aluminum alloy bar containing a Friction Stir Weld and subjected to ex-situ three-point bending. ‘Polar transformation’ method shows good agreement with the traditional ‘caking’ technique, but also exhibits excellent speed, and robustness.