铍材中子衍射应力测试的参数及其优化

Optimization of the Neutron Diffraction Stress Measurement Parameters of Beryllium

利用铍环焊接样品进行了铍材在稳态堆上中子衍射应力测试的参数及其优化研究。结果表明:在中子束波长0.1587 nm和中子注量率2×10~6 n·cm^(-2)·s^(-1)的条件下,铍材中子衍射应力测试可以选取Be(110)晶面,衍射角为88.2°,规范体积为2 mm×2 mm×2 mm,初次测试采用时间为120 s,对单点进行4次重复性测试,表明衍射强度计数存在明显波动,测试应变的最大偏差接近300με,延长时间至6000 s后测试,表明衍射曲线较为平滑,重复性好,测试应变的最大偏差减小至50με以内,相应铍材的应力测试精度约15 MPa;利用优化参数对焊接铍环焊缝附近的环向应变进行了测试,表明分布规律与国外文献报道趋势基本一致,进一步开展铍材的中子衍射应力测试奠定了基础。

The parameters of neutron diffraction stress measurement of beryllium on a steady-state reactor have been optimized using a welded beryllium ring. The results show that under the condition of the neutron beam wavelength of 0.1587 nm and neutron flux rate of 2×10^6 n·cm^-2·s^-1, the neutron stress measurement for beryllium can use Be（110） plane, with the diffraction angle 88.2° and the gauge volume 2 mm ×2 mm ×2 mm. In the first test, the measuring time is 120 s. After 4 runs test at a fixed location, the diffraction curve has an obvious intensity fluctuation and the maximum strain error is about 300 με. Afterwards, the measuring time extends to 6000 s, revealing the diffraction curve is smooth and has good repeatability. The maximum strain error decreases to less than 50 με, and the corresponding stress error for beryllium is 15 MPa. The hoop strain in beryllium ring near the weld line has been measured using the optimized parameters. It indicates the hoop strain trend is basically identical to the literature. This study can establish a basis for the stress measurement of beryllium by neutron diffraction.