Development of high precision evaluation system of fatigue damage by time-of-flight neutron method

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(1) The diffraction elastic constants for calculating the stress from the strain were determined for several structural materials on the basis of the diffraction intensity. The accuracy of the stress measurement was clarified.(2) Stress measurement in the smooth specimens of aluminum alloy reinforced with SiC particles under monotonic axial loading was carried out. In the composites, the phase stress in the constituent phase was measured. The diffraction plane and diffraction intensity for stress measurement were determined on the basis of the confident limit. Fatigue damage could be determined from the change of the profile broadening.(3) Fatigue tests of an austenitic stainless steel SUS316NG were conducted under axial tension compression. The change of the profile broadening was measured during fatigue process. When the large compressive residual stress was induced by the machining, the compressive residual stress decreased in the early stage at the higher applied stress amplitude. On the other hand, for the lower stress amplitude, the change of the residual stress is small.(4) For the stress measurement of the welded components, the second kind of stress is important to determine the macro stress. In that case, the use of the small piece as a reference of the stress free lattice spacing is effective. The residual stress in the butt welded joint could be determined.(5) The line broadening in the ultrafine-grained Cu fabricated by ECAP method increased with the plastic strain. The value, however, decreased to the initial value during unloading. The change of the line broadening under fatigue loading is not so large.(6) Performance evaluation of the radial collimator to limit the gage volume of lmm was conducted. The measured profile was identical to the result of the simulation. The stress can be measured with enough accuracy.