共查询到20条相似文献,搜索用时 15 毫秒
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D Petrascheck 《Canadian Metallurgical Quarterly》1987,35(13):6549-6553
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T Inada Y Hayakawa J Tada N Kubota T Hiraoka S Sato 《Canadian Metallurgical Quarterly》1993,25(3):499-504
A neutron irradiation facility was constructed at PARMS, University of Tsukuba to produce an ultrahigh energy neutron beam with a depth dose distribution superior to an x-ray beam generated by a modern linac. This neutron beam was produced from the reaction on a thick uranium target struck by a 500 MeV proton beam from the booster synchrotron of the High Energy Physics Laboratory. The percentage depth dose of this neutron beam was nearly equivalent to that of x-rays around 20 MV and the dose rate was 15 cGy per minute. The relative biological effectiveness (RBE) of this neutron beam has been estimated using the cell inactivation effect and the HMV-I cell line. The survival curve of cells after neutron irradiation has a shoulder with n and Dq of 8 and 2.3 Gy, respectively. The RBE value at the 10(-2) survival level for the present neutron beam as compared with 137Cs gamma rays was 1.24. The results suggest that the biological effects of ultrahigh energy neutrons are not large enough to be useful, although the depth dose distribution of neutrons can be superior to that of high energy linac x-rays. 相似文献
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D. W. Brown M. A. M. Bourke C. N. Tomé R. Varma T. M. Holden B. Clausen 《Metallurgical and Materials Transactions A》2003,34(7):1439-1449
The deformation of polycrystalline beryllium to strains of ±0.8 pct in uniaxial tension and compression was studied by neutron
diffraction and modeled using an elasto-plastic self-consistent (EPSC) model. The beryllium response is asymmetric with respect
to tension and compression in both the macroscopic behavior, as displayed in the stress/strain curve, and the microscopic
lattice response. The EPSC model qualitatively reproduces the lattice strain curves in tension and compression with the assumption
of pyramidal slip being active, in addition to prism and basal slip and with the inclusion of thermal residual stresses developed
during processing. Although it underpredicts the magnitude of the observed strains, it demonstrates that accounting for residual
stresses of thermal origin is crucial for understanding the evolution of lattice strains during uniaxial loading. 相似文献
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R Lagercrantz 《Canadian Metallurgical Quarterly》1977,74(17):1710-1713
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Uniaxial tensile deformation of uranium 6 wt pct niobium: A neutron diffraction study of deformation twinning 总被引:2,自引:0,他引:2
D. W. Brown M. A. M. Bourke M. G. Stout P. S. Dunn R. D. Field D. J. Thoma 《Metallurgical and Materials Transactions A》2001,32(9):2219-2228
The deformation of polycrystalline uranium 6 wt pct niobium (U6Nb) was studied in situ during uniaxial tensile loading by time-of-flight neutron diffraction. Diffraction patterns were recorded at incremental
stresses to a maximum of 450 MPa (∼4 pct macroscopic strain). Consistent with reorientation of the martensite variants by
twinning, significant changes in the diffraction peak intensities, which were proportional to the plastic contribution of
the macroscopic strain, were observed. Both the lattice parameters (a, b, c, and γ) and interplanar spacings (d
hkl
) were determined as a function of applied stress. Phenomenologically, the highly anisotropic stress response of the lattice
parameters as well as the individual lattice spacings can be related to deformation twinning. Preliminary transmission electron
microscopy (TEM) studies identified the (
30) and (
72) as active deformation twinning systems of U6Nb in tension. 相似文献
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The uniaxial behavior of aluminum polycrystals is simulated using a rate-independent incremental self-consistent elastic-plastic
polycrystal deformation model, and the results are evaluated by neutron diffraction measurements. The elastic strains deduced
from the model show good agreement with the experimental results for the 111 and 220 reflections, whereas the predicted elastic
strain level for the 200 reflection is, in general, approximately 10 pct too low in the plastic regime. 相似文献
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