Error Analysis of Near-Field High Energy Diffraction Microscopy

Among non-destructive characterization techniques able to probe the properties of bulk polycrystals, High Energy Diffraction Microscopy (HEDM) has become the method of choice for researchers seeking spatial resolution of grain orientations and strain states. From HEDM data collected in the near field, the forward modeling method (FMM) of reconstruction is capable of producing micro-scale resolution of the orientation field, despite complex grain morphologies and significant plastic strains. In this thesis, the accuracy of the FMM reconstruction is examined through direct comparison with an Electron Backscatter Diffraction (EBSD) measurement of a pure gold specimen. The sensitivity of the FMM reconstruction to its inputs is probed through a series of simulations. Given raw diffraction data collected under optimum experimental conditions, spatial resolution is found to be accurate to within intrinsic limits set by the experimental equipment. Resolution of reconstructed crystallographic orientations is found to be <0:05^o. Input parameters most likely to cause reconstruction errors are identified, and a novel method is proposed to determine proper values for experimental inputs. Two case studies are also presented.