分类: 物理学 >> 核物理学 分类: 核科学技术 >> 核聚变工程技术 提交时间: 2024-02-27
摘要: The helium bubbles induced by 14 MeV neutron irradiation can cause intergranular fractures in reduced activation ferritic martensitic (RAFM) steel, which is a candidate structural material for fusion reactors. In order to elucidate the susceptibility of different grain boundaries (GBs) to helium-induced embrittlement, the tensile fracture processes of 10 types of GBs with and without helium bubbles in body-centered cubic (bcc) iron at the relevant service temperature of 600 K were investigated via molecular dynamics methods. The results indicate that in the absence of helium bubbles, the GBs studied here can be classified into two distinct categories: brittle GBs and ductile GBs. The atomic scale analysis shows that the plastic deformation of ductile GB at high temperatures originates from complex plastic deformation mechanisms, including the Bain/Burgers path phase transition and deformation twinning, in which the Bain path phase transition is the most dominant plastic deformation mechanism. However, the presence of helium bubbles severely inhibits the plastic deformation channels of the GBs, resulting in a significant decrease in elongation at fractures. For bubble-decorated GBs, the ultimate tensile strength increases with the increase of the misorientation angle. Interestingly, the coherent twin boundary Ʃ3{112} was found to maintain relatively high fracture strength and maximum failure strain under the influence of helium bubbles.
分类: 核科学技术 >> 核聚变工程技术 提交时间: 2017-10-27
摘要: Purpose – The purpose of this paper is to develop a serial redundant manipulator system applied in nuclear fusion environment. It will allow remote inspection and maintenance of plasma facing components in the vacuum vessel of fusion device without breaking down the ultra-high vacuum condition during physical experiments. Design/methodology/approach – Firstly, considering the dynamic sealing of actuators to avoid polluting the vacuum condition inside fusion reactor, the mechanical design of robot system has been introduced. The redundant manipulator system has 11 degree of freedoms in total with an identical modular design. Besides, to improve the position accuracy, an error prediction model has been built based on the experimental study and back-propagation neural network (BPNN) algorithm. Findings – Currently, the implementation of the manipulator system has been successfully finished in both atmosphere and vacuum condition. The validation of BPNN model shown an acceptable prediction accuracy (94%~98%) compared with the real measurement. Originality/value – This is a special robot system which is practically used in a nuclear fusion device in China. Its design, mechanism and error prediction strategy have great reference values to the similar robots in vacuum and temperature applications.
分类: 核科学技术 >> 核聚变工程技术 提交时间: 2017-10-27
摘要: Structured Abstract: Purpose: EAST is a tokamak fusion device running in ultra-high vacuum condition. To avoid polluting the inner vessel environment, solid lubrication has been applied on the surface of bearings and gears which exposed to the vacuum. Design/methodology/approach: anti-friction MoS2 coatings penetrating with different atoms have been developed by multi-target magnetron sputtering deposition technique. This paper presents the comparative testing of tribological properties for three kinds of MoS2-based coating layers. Findings: based on the test results, MoS2-Ti-C coating films are supposed to be the final selection due to the better performance of friction coefficient and lubrication longevity. Originality/value: finally, the detailed information has been characterized for the hybrid coatings which can provide some references for applications of solid lubrications in similar condition of high vacuum and temperature.