Development of nondestructive evaluation system of fatigue damage by neutron diffraction

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1. A method to estimate the diffraction elastic constants of engineering materials was proposed on the basis of Eshelby's inclusion mechanics combined with the self-consistent model.2. The residual stress analyzer (RESA) was developed at the guide tube of T2-1 of the reactor, JRR-3M, at Japan Atomic Energy Research Institute (JAERI). To determine the distribution of the residual stress, an automatic devise for positioning and a bent crystal system for focusing were newly developed.3. The stress partioning of aluminum reinforced by SiC particles agrees very well with the prediction by micromechanics. The measured values of thermal residual stresses in alumina mixed with zirconia or with silicon carbide agreed with the prediction from the mismatch of the thermal expansion coefficient by micromechanics.4. The developed system for neutron stress measurements was successfully applied to measure the residual stress distribution in aluminum shrink fit, jacket material for ITER superconducting coil, and welded pipes.5. The change of the residual stress was detected by neutron diffraction at the time of crack initiation in fatigue of notched carbon steel bars. The redistribution of the residual stress due to crack propagation was detected by neutron diffraction near the weld joint of stainless pipes.6. A method was proposed toward standardization of neutron stress measurements.