Advanced Non-Destructive System to Characterize Subsurface Residual Stresses in Turbo-machinery Components

Surface enhancement methods, such as shot peening (SP), laser shock peening (LSP), and low-plasticity burnishing (LPB), can introduce beneficial near-surface compressive residual stress and significantly improve the fatigue resistance and foreign object damage tolerance of aerospace components such as superalloy turbine fans, disks, and integrally bladed rotors (IBR). Residual stress, however, relaxes with usage. To predict the remaining useful life (RUL) for those critical components, accurate and reliable residual stress profile data in the subsurface region are required. X-ray diffraction (XRD) is the only acceptable nondestructive evaluation (NDE) method for residual stress assessment, which is limited to an extremely thin (less than 20 ?m deep) surface layer. Alternative NDE methods, including the most promising Eddy Current Conductivity Spectroscopy (ECCS) and Surface Acoustic Wave (SAW) technology, have been studied for years, but none of them can provide reliable subsurface residual stress assessments. To address this critical need, X-wave Innovations, Inc. (XII) with Lockheed Martin (LM) Cooperation, propose to develop a novel NDE tool for subsurface residual stress measurements in surface-enhanced aerospace structural components. In the Phase I program, we will focus on the prototype system development and demonstrate the feasibility of the proposed approach. For the Phase II program, we will refine the prototype system with improved hardware and software and validate its performance for subsurface residual stress measurements. For the Phase III program, we will focus on the optimization of the system performance, as well as the transitioning of the developed technology.