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Study of theoretical tensile strength of Fe by afirst-principles computational tensile test 下载免费PDF全文
This paper employs a first-principles total-energy method to
investigate the theoretical tensile strengths of bcc and fcc Fe
systemically. It indicates that the theoretical tensile strengths
are shown to be 12.4, 32.7, 27.5~GPa for bcc Fe, and 48.1, 34.6,
51.2~GPa for fcc Fe in the [001], [110] and [111] directions,
respectively. For bcc Fe, the [001] direction is shown to be the
weakest direction due to the occurrence of a phase transition from
ferromagnetic bcc Fe to high spin ferromagnetic fcc Fe. For
fcc Fe, the [110] direction is the weakest direction due to the
formation of an instable saddle-point `bct structure' in the tensile
process. Furthermore, it demonstrates that a magnetic instability
will occur under a tensile strain of 14%, characterized by the
transition of ferromagnetic bcc Fe to paramagnetic fcc Fe.
The results provide a good reference to understand the intrinsic
mechanical properties of Fe as a potential structural material in
the nuclear fusion Tokamak. 相似文献
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报道了HL-2A装置密度极限附近边缘剪切流和极向剩余胁强的最新实验研究结果。研究发现,等离子体密度向Greenwald密度靠近时,等离子体响应由绝热响应向流体动力学响应转变,导致湍流雷诺胁强中的非扩散项——剩余胁强降低,其径向梯度表征的等离子体自发旋转力矩显著降低。边缘极向流的湍性驱动降低进一步导致边缘E×B极向流剪切强度减弱。这些实验结果证明了湍流剩余胁强的降低是导致托卡马克密度极限附近边缘极向剪切层崩塌的关键因素。 相似文献
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