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991.
Li Peng Ji Shengqin Zeng Xiaoyan Hu Qianwu Xiong Weihao 《International Journal of Machine Tools and Manufacture》2007,47(6):996-1002
Direct laser fabrication (DLF) is an advanced manufacturing technology, which can build full density metal parts directly from CAD files without using any modules or tools. The investigation on the fabrication of thin-walled parts of nickel alloy using open-loop DLF process is introduced in this paper. The experimental setup consisted of a CO2 laser, a 3-axis CNC table, a coaxial powder nozzle and a powder recycler. The 3D-CAD file of a thin-walled metal part was converted into the STL file format and imported into software HUST-RP to generate ‘pseudo-random’ scanning paths of laser beam. The influence of process parameters on the build height of thin-walled metal parts was studied by 1–10 layered single-bead stacks of nickel alloy. The result shows that the interference factors which affect the build height of thin-walled metal parts occur randomly during the process. For open-loop DLF process, thin-walled metal parts can achieve much better shape quality if the process parameters are suitable. Multilayer single-bead walls were built up with different scanning velocity to obtain the optimal process parameters of thin-walled parts of nickel alloy. It shows that thin walls of nickel alloy with uniform height can be built up layer by layer in a certain range of specific energy. However, it is difficult to control the build height of complex thin-walled metal parts in an accurate manner just using optimal parameters. A special coaxial powder nozzle was designed in this paper. In a certain range, the deposition thickness of the nozzle is nearly linearly increased with increase in the standoff distance between the powder focusing point of the nozzle and the deposition substrate. By means of the nozzle, a novel method to control the build height of thin-walled metal parts using open-loop DLF process was introduced. The difference in build height of a thin-walled part can be compensated automatically in one or several layers during the process. It is proved that the build height of a thin-walled metal part can be accurately controlled in theory using the nozzle. A complex single-bead part of nickel alloy whose geometry was designed to be the well-known Chinese ‘FU’ was fabricated and explained in this paper. The result shows that the shape quality of the sample is quite good, and actual build height of the sample is 53.54 mm while the designed value is 54 mm. 相似文献
992.
Auger electron spectroscopy in combination with depth profiling by Ar ion sputtering was employed as a surface analytical technique to determine the positions of thin (3–5 nm) inert Pd markers during growth of oxide films on Al, Ni, and -NiAl. Alumina films 35 and 120 nm thick formed on Al and -NiAl, respectively, grew by inward diffusion of oxygen. Metal migration accounted predominantly for the growth of a NiO film 150 nm thick on the (111) crystal face of Ni. However, an assessment could not be made with respect to oxygen diffusion, if any, in this film due to the limitations imposed on precise depth profiling of the marker position caused by uneven sputtering of the oxide and metal phases. 相似文献
993.
薄膜厚度对HfO2薄膜残余应力的影响 总被引:1,自引:0,他引:1
HfO2薄膜是用电子束蒸发方法制备的,利用ZYGO干涉仪测量了基片镀膜前后曲率半径的变化,计算了薄膜应力。对样品进行了XRD测试,讨论了膜厚对薄膜残余应力的影响。结果发现不同厚度HfO2薄膜的残余应力均为张应力,应力值随薄膜厚度的增加而减小,当薄膜厚度达到一定值后,应力值趋于稳定。从微观结构变化对实验结果进行了分析,发现微结构演变引起的本征应力变化是引起薄膜残余应力改变的主要因素。 相似文献
994.
钢管斜轧延伸时辊型对附加变形的影响 总被引:1,自引:0,他引:1
用电子束标迹法研究了钢管斜轧延伸时辊型对附加变形的影响,研究表明,锥形辊与鼓形辊相比,可使附加变形显著减少。 相似文献
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997.
研究开发了冷固结含碳铁矿球团的还原工艺,它与环形转底炉相结合,形成快速直接还原新工艺,生产金属此球团,具有一系列优点,如:设备简单,生产效率高、能耗低等等。 相似文献
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1000.
邢九平 《水科学与工程技术》2015,(2):72-75
为更好地完成南水北调中线元氏1标石渠段的渠坡衬砌,采用了滑膜施工工艺进行施工,加强和改善了石渠段边坡的整体稳定性和强度,进而保证了石渠段衬砌混凝土的质量,也为类似工程提供了借鉴。 相似文献