NDI System for Quantification of Subsurface Residual Stress in the Laboratory

The goal of the proposed research is to develop a non-destructive method for subsurface residual stress measurement in turbo-machinery components. Neutron diffraction techniques have a proven ability to determine residual stresses at significant depths, however implementation of these techniques has been limited to specialized facilities such as the High Flux Isotope Reactor (HFIR) neutron at Oak Ridge National Lab. Advances in laboratory based neutron generators have now created the possibility to implement some of these techniques in laboratory and/or production environments. We plan to exploit the improved capabilities of these generators to realize a practical method that will enable determination of residual stresses throughout large components or bulk materials. The proposed non-destructive evaluation method will combine advantages of conventional in-situ neutron diffraction with energy selective neutron imaging to reveal microstructural information related to the lattice spacing such as phase, texture, and strain. The Phase I program will demonstrate feasibility of our novel method whereas the Phase II program will logically extend Phase I research to implement a practical system. To successfully develop this challenging but highly rewarding technology, we have formed a strong consortium that includes a world renowned expert in experimental measurements of residual stress using neutron and x-ray techniques and an OEM for turbo-machinery, which will effectively address current needs of the Navy.