Advanced NDI/E Tool for Residual Stress Management

Fatigue properties of metallic aerospace structures are improved significantly by cold working to impart favorable compressive residual stresses (RS) at and near the surface. In Phases I and II, Proto designed and developed a first generation x-ray diffraction (XRD) based NDI/E tool to measure RS distributions surrounding cold-worked holes in aerospace structures. Subsequently, Proto self-funded and developed an improved second-generation RS measurement (RSM) tool XRD. These tools work well on aircraft skins and exposed structures where the radii of curvature are large. However, those tools are quite limited in their ability to reliably measure RS on parts with complex geometries and to access tight and confined spaces of typical structures. The proposed third generation RSM tool is designed to overcome both of those limitations by miniaturizing the x-ray source, optimizing the detectors, and refining the probe design. The final RSM tool will be computer controlled, handheld and/or hand-placeable, and safe with integrated shielding. It will have a detachable small display on the probe for real time RS readout and will store measurements in a database for future analysis and tracking. The system will be small, lightweight, portable, rugged, and operate on 110 VAC for use aboard ship and in depots.