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岩本 ちひろ*; 高村 正人*; 上野 孝太*; 片岡 美波*; 栗原 諒*; 徐 平光; 大竹 淑恵*
ISIJ International, 62(5), p.1013 - 1022, 2022/05
被引用回数：2 パーセンタイル：32.54(Metallurgy & Metallurgical Engineering)Neutron diffraction is a powerful non-destructive method for evaluating the microscopic structure and internal stress of metal plates as a bulk average. Precise neutron diffraction measurements with a high intensity neutron beam have already been carried out at large-scale neutron facilities. However, it is not easy to provide users with enough experimental opportunities. We are working on upgrading the neutron diffractometer with techniques of time-of-flight to enable stress measurements at RIKEN accelerator-driven compact neutron source (RANS). To improve neutron diffraction resolution, delayed neutrons, which expand neutron beam pulse width, should be suppressed. However, it is difficult to separate the delayed neutrons experimentally. In this study, a new analysis method has been proposed to deconvolute the diffraction peak from the delayed neutron component. Moreover, a new collimator system, called decoupled collimator system, has been developed to reduce the number of delayed neutrons. The diffraction patterns from a powder sample of pure body-centered cubic iron were measured with the decoupled collimator and the diffraction peak of {211} reflection was analyzed by the new analysis method using a model function of a single exponential decay function convoluted with a Gaussian function. By this method, the decoupled collimator system has been confirmed to achieve a smaller measurement limit of lattice strain 
than a small-aperture polyethylene collimator system and a non-collimator system. The currently available was 6.7
10
, this means that the internal stress up to 130 MPa can be well evaluated for steel materials with a Young's modulus of 200 GPa at RANS.
徐 平光; 岩本 ちひろ*; 高村 正人*; 大竹 淑恵*; 栗原 諒*; 上野 孝太*; 片岡 美波*; 山本 和喜; Harjo, S.; 菖蒲 敬久
no journal, ,
Neutron diffraction can collect sample-volume averaged diffraction patterns due to the excellent penetrability and the coarse beam spot, valuable for investigating bulk microstructure changes of polycrystalline materials. In recent years, several neutron instruments in Japan have been employed for precise bulk texture evaluation. The engineering materials diffractometer attached with large sample stage and precise radial collimators at J-PARC has realized a reliably combined Rietveld texture evaluation, simultaneously providing crystallographic textures and other profile-analysis-related material parameters such as crystal structures, stress tensors. The RANS compact neutron source has enabled reliable bulk texture evaluation of steel materials through reasonably using a high stereographic angle resolution and a large sample-gauge volume. As a feed-back from the texture measurement technique based on RANS compact neutron source, recently, weak diffraction patterns step-by-step collected in very short time from RESA neutron diffractometer at JRR-3 have been utilized to realize the precise texture evaluation of various polycrystalline materials, 
, a standard rock material, and different steel materials.
岩本 ちひろ*; 高村 正人*; 上野 孝太*; 片岡 美波*; 栗原 諒*; 徐 平光; 大竹 淑恵*
no journal, ,
Neutron diffraction is a powerful non-destructive method for evaluating the microscopic structure and internal stress of metallic materials and related semi-finished parts as a bulk average. To implement on-site stress measurements via the neutron diffraction at laboratories and factories frequently and even daily, we are establishing and upgrading the novel measurement and analysis methodology of time-of-flight neutron diffraction at RIKEN accelerator-driven compact neutron source (RANS). In this study, we have proposed two methods to improve the determination resolution of the diffraction peak position by focusing on delayed neutrons due to background scattering from devices such as reflector surrounding the neutron moderator and the polyethylene collimator. First, an analysis method has been proposed to deconvolute original diffraction peak from the delayed neutron component by defining a new model function to well describe the profile shape of delayed neutron diffraction. Second, a new decoupled collimator system has been developed to reduce the number of delayed neutrons. The diffraction patterns from a powder sample of pure body-centered cubic iron were measured with the decoupled collimator and the diffraction peak of {211} reflection was analyzed by the new analysis method using the neutron diffraction profile model function, 
, a single exponential decay function convoluted with a Gaussian function. By this method, the decoupled collimator system has been confirmed to achieve a smaller measurement limit of lattice strain 
than a small-aperture polyethylene collimator system and a non-collimator system. The currently available was 6.710, which means that the internal stress up to 130 MPa can be well evaluated at RANS for steel materials with a Young's modulus of 200 GPa.
