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- 저자 : Julong Yuan (검색결과 3 건)
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Jinhu Wang,Qingliang Zhao,Chunyu Zhang,Bing Guo,Julong Yuan 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.4
In order to improve the grinding wheel wear during the sapphire steep aspheric surface grinding process, a SiC-reinforced resin-bonded hemispherical diamond wheel was used and the arc envelope grinding performance was investigated. Firstly, the mapping relationship between the contours of the grinding wheel and the aspheric surface was established based on the grinding conditions. The wear of the hemispherical diamond wheel was modelled, and the result indicates that the maximum wear occurred at the edge of the hemisphere, decreases along the generatrix and increases near the center. Then, the formtrued diamond wheel was used for grinding the sapphire steep aspheric surface. The concave and convex surface form error obtained at the central part of Φ 50 mm are 2.5 μm and 1.3 μm, respectively. The surface roughness R a is 230–450 nm, which is affected by the material removal rate and the sapphire crystal anisotropy. The SiC-reinforced resin-bonded diamond wheel possesses favorable self-sharpening ability and sufficient diamond grain retention capacity for sapphire grinding. The wear distribution shows that the most severe wear parts of the grinding wheel are at the edge and the center of the grinding zone, which is consistent with the model-predicted results.
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Effect of surface quality on hydrogen/helium irradiation behavior in tungsten
Hongyu Chen,Qiu Xu,Jiahuan Wang,Peng Li,Julong Yuan,Binghai Lyu,Jinhu Wang,Kazutoshi Tokunaga,Gang Yao,Laima Luo,Yucheng Wu 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.6
As the plasma facing material in the nuclear fusion reactor, tungsten has to bear the irradiation impact ofhigh energy particles. The surface quality of tungsten may affect its irradiation resistance, and even affectthe service life of fusion reactor. In this paper, tungsten samples with different surface quality werepolished by mechanical processing, subsequently conducted by D2þ implantation and thermal desorption. D2þ implantation was performed at room temperature (RT) with the irradiation dose of 1 1021D2þ/m2 by 5 keV D2þ ions, and thermal desorption spectroscopy measurements were done from RT to900 K. In addition, He irradiation was also performed by 50 eV Heþ ions energy with the fluxes of5.5 1021 m2s1 and 1.5 1022 m2s1, respectively. Results reveal that the hydrogen/helium irradiation behavior are both related to surface quality. Samples with high surface quality has superior D2þretention behavior with less D2 retained after implantation. However, such samples are more likely togenerate fuzzes on the surface after helium irradiation. Different morphologies (smooth, wavy, pyramids)after helium irradiati
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Zhe Wu,Yuying Zhang,Yong Liu,Fangli Mo,Chengwu Wang,Huizong Lu,Julong Yuan,Zhifeng Liu 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.25 No.1
Aiming to green machining of single crystal sapphire, polysaccharide-bonded soft abrasive tool using hydrothermal gelatinisation method was proposed. Mechanical properties of prepared polysaccharide films show that when the weight ratio of natural polysaccharide to cross-linked polysaccharide is 1:1, the tensile strength and extension rate of the film are relatively optimal. Composition and making process of polysaccharide bonded abrasive tool was built. Samples of polysaccharide bonded soft abrasive tools were made by which the single crystal sapphire substrates were machined. It is found that by adopting guar gum as dispersion agent and hydrothermal gelatinisation, the abrasive sedimentation during making process of abrasive tool is substantially eliminated, and better abrasive holding ability is attained. XPS and Raman microscope analysis showed that material of single crystal sapphire was removed by mechano-chemical reaction with good surface integrity. Abrasive tools with abrasive to binder ratio of 4:1 presented relatively better self-sharpening and machining performance, and the material removal rate reached 0.427 μm/min. More interesting, XPS and FT-IR analyses both indicated that the polysaccharide binder dehydrated by the friction heat during machining process.
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