Residual stress measurements in the complex geometry inherent to split sleeve cold expanded holes

The aerospace industry is continuously challenged with the task of increasing the performance and extending the service life of both legacy and new flight systems, in a reliable and cost effective manner. In recent decades, engineered residual stresses have shown great potential in achieving that end via several processes including: conventional shot peening, laser shock peening, split-sleeve cold expansion, and others. However, many of the components that stand to benefit most from the application of engineered residual stresses have complex geometric features that often make accurate and reliable experimental residual stress measurements difficult to execute. Moreover, relatively steep residual stress gradients imparted by various engineered processes can add to measurement difficulty whereby highly localized residual stress maxima or minima may require very fine spatial resolution. In the current study it will be shown how x-ray diffraction techniques were used in the characterization of residual stress in split-sleeve cold expanded holes where both complex geometry and steep residual stress gradients are present. Specific case studies will be examined and the significance of the findings will be presented. The intent of this presentation is to assist others when developing their own test methodologies to better understand how high quality residual measurement stress data can be obtained on split-sleeve cold expanded holes using x-ray diffraction techniques.