Residual Stress Measurements Program to Support Condition Based Maintenance (CBM) of Critical Rotating Components of Propulsion Systems

Surface enhancement processes are extensively used to introduce compressive residual stresses (CRS) and enhance the fatigue performance in titanium and nickel alloy rotating components for Navy propulsion systems. CRS can relax in rotating components as a result of thermal exposure and cyclic stresses, adversely impacting the fatigue life and strength. Relaxation can occur rapidly depending upon the relative component temperatures and cyclic stresses. Inspection of the components is performed on a routine basis to characterize damage levels in accordance with Technical Manuals (TM). However, the CRS are currently not monitored and tracked during routine inspection. As part of the inspection cycle, components are re-shot peened to overcome any residual stress relaxation that may have occurred. Intervals at which the components are re-peened may or may not be appropriate for the rate of compressive relaxation. A portable XRD measurement device capable of quickly quantifying the CRS would allow the Navy to track the surface residual stress in support of condition based maintenance of critical components. The measurement device would allow for field measurement of critical features of blades and disk components. The device would be capable of not only measuring the surface residual stress but also the cold working which has a significant impact on the rate of relaxation.