Development of high precision measurement system of residual stress in engineering materials by time-of-flight neutron method

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Tensile testing machine was installed at the Sirius in the High Energy Accelerator Research Organization (KEK). By using the tensile testing machine, in-situ strain measurement can be carried out during tensile loading. The methods of stress measurement for single crystals and multi-phase polycrystalline materials were proposed. The effect of porosity on the elastic constants was investigated by the proposed method. Evaluation method of elastic constant of single crystals on the basis of a number of diffraction constants measured with poly-crystals was proposed. Further more, a simplified method to predict the diffraction elastic constant for arbitrary diffraction plane by using the elastic constant of single crystals was proposed. For the engineering materials, residual stress and loading stress of quenched steels, metal matrix composites, ceramics matrix composites and shape memory alloys were measured. For the composites, the loading stress and the residual stress can be evaluated by the micro mechanics models by considering that the one of the constituent phase is inclusion. To determine the lattice strain with sufficient accuracy, the diffraction intensity must be larger than 300 counts. The lattice strain can be evaluated by a single peak analysis and the Rietveld analysis by using full diffraction patterns.