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| 1 | Study on stable delivery of charged uniform droplets for freeform fabrication of metal parts显示文摘Electrostatic delivery of charged uniform metal droplets is a novel method to deposit metal parts with short process period and low cost. But the delivery process is unstable and delivery accuracy of charged droplets deteriorates because of actions of mutual interactions of closely charged droplets. A droplet generator with droplet charging and deflecting system has been established to find out the way for stably and accurately deflecting droplets. The parameters for generating uniform droplets were first studied. Then the droplet deflections and metal parts depositions with different charge methods were discussed. The results show that the unbalanced electrostatic repelling forces are the main factor to cause the unstable deflection of droplets. The droplets deflection distance can be predicted and controlled by balancing the repelling forces of charged droplets. The metal parts are stably deposited after combining the board charged pulse and substrate motion, indicating that the work can provide useful theoretical and experimental guide for droplet-based freeform fabrication. | LUO Jun QI LeHua ZHOU JiMing XIAO Yuan YANG Fang | 2011 | Science China(Technological Sciences)2011，54，7： | 7 |
| 2 | Influence of Interfacial Bonding between Metal Droplets on Tensile Properties of 7075 Aluminum Billets by Additive Manufacturing Technique显示文摘7075 aluminum billets were fabricated by micro droplet deposition manufacturing technique,and the influence of interfacial bonding between metal droplets on the tensile properties was studied.Three sets of samples were manufactured under different temperature conditions,and their mechanical properties were compared.The results show that the temperature of the metal droplets and substrate signi?cantly affect the tensile strength of the sample.Moreover,with proper temperature setting,the 7075 aluminum billets manufactured by micro metal droplet deposition could achieve very good mechanical properties with a tensile strength of 373 MPa and an elongation of 9.95%,which are very similar to those of an extruded sample.Moreover,a metallurgical bonding diagram based on numerical calculations of interfacial temperature was established to predict the interfacial bonding state.In addition,the fracture morphologies of these specimens were observed.It is indicated that there was a signi?cant transformation of failure mechanism with the improvement of metallurgical bonding,which agreed well with the numerical results. | Hansong Zuo Hejun Li Lehua Qi Songyi Zhong | 2016 | Journal of Materials Science & Technology2016，32，5： | 6 |
| 3 | Effect of Temperature on the Synthesis of SiC Coating on Carbon Fibers by the Reaction of SiO with the Deposited Pyrolytic Carbon Layer显示文摘The influence of reaction temperature on the preparation of SiC coating on carbon fibers by the reaction of silicon monoxide with the deposited pyrolytic carbon (PyC) layer has been discussed.With rising reaction temperature,the thickness of SiC layer increases and the SiC grain is coarsening.The apparent activation energy for the synthesis of SiC layer is about 103.3 kJ/mol.The oxidation resistance of carbon fiber can be improved by the SiC/PyC layers significantly.The initial oxidation temperature of the SiC/PyC coated carbon fiber is about 300℃ higher than that of the uncoated carbon fiber.The oxidation of the SiC/PyC coated carbon fiber is owing to the diffusion of oxygen through the cracks generated by the mismatch of thermal expansion. | Hejun Li,Haibo Ouyang,Lehua Qi,Yulei Zhang,Zhengjia Li and Jianfeng Wei C/C Composites Research Center,Key Laboratory of Ultrahigh Temperature Composites,Northwestern Polytechnical University,Xi an 710072,China | 2010 | Journal of Materials Science & Technology2010，26，3： | 5 |
| 4 | Control System Development and Experimental Study on Ultrasonic Vibration Feeding显示文摘Ultrasonic vibration feeding(UVF) method which can quantitatively feed and precisely deposit fine powder is a potential technique for micro feeding.The excitation sources transmit vibration to capillary though the third medium for most UVF devices.The vibrator is directly touched with the capillary can transmit mechanical energy on the capillary as much as possible,and the powder feeding can be controlled more precise.However,there are few reports about it.A direct UVF system which integrates the function of micro feeding,process observing,and powder forming was developed in this work.In order to analyze the effect of the system factors on feeding,a group of L9(33) orthogonal experiments are selected to confirm the effect of level change of factors.The three factors are capillary nozzle diameter,amplitude and signal.The flow rate was stable for each combined factors,and the optimum combination for the minimum flow rate are choosing small capillary,small amplitude,and triangular wave orderly.The whole process of feeding includes start point,middle stage and stop stage.Starting of feeding was synchronized to vibration when the amplitude of capillary nozzle is larger than critical amplitude.Then,the feeding process enters the middle stage,the feeding state is observed by the CCD,and it is very stable in the middle stage.Overflow of feeding can't be eliminated during the stop stage.The features of the deposited powder lines are analyzed;the overflow can be diminished by choosing small capillary and appropriate ratio of the capillary nozzle diameter to the particle size.Chinese characters lattices were deposited to validate the ability of quantitatively feeding and fixed feeding of UVF.Diameters of all powder dots show normal distribution,and more than 60% dots are concentrated from 550 μm to 650 μm,and the average diameter for all the dots is 597 μm.Most dots positions are well approached to their scheduled positions,and the maximum deviation is 0.27 mm.The new direct UVF system is used to implement experiments,which confirms the precise controllable of feeding.According improve the feeding technique,it suits well for rapid prototyping,chemistry,pharmaceutics and many other fields,which require precise measurement and feed minim powder. | ZENG Xianghui QI Lehua HUANG Hua LI Yang YANG Fang | 2011 | Chinese Journal of Mechanical Engineering2011，24，6： | 5 |
| 5 | Microstructure and tensile behavior of 2D-C_f/AZ91D composites fabricated by liquid–solid extrusion and vacuum pressure infiltration显示文摘2D carbon fiber reinforced AZ91 D matrix composites(2D-C_f/AZ91 D composites) were fabricated by liquid–solid extrusion and vacuum pressure infiltration technique(LSEVI). In order to modify the interface between fibers and matrix and protect the fiber, pyrolytic carbon(Py C) coating was deposited on the surface of T700 carbon fiber by chemical vapor deposition(CVD). Microstructure observation of the composites revealed that the composites were well fabricated by LSEVI. The segregation of aluminum at fiber surface led to the formation of Mg_(17)Al_(12) precipitates at the interface. The aluminum improved the infiltration of the alloy and Py C coating protected the fibers effectively. The ultimate tensile strength of 2D-C_f/AZ91 D composites was about 400 MPa. The fracture process of 2D-C_f/AZ91 D composites was transverse fiber interface cracking–matrix transferring load–longitudinal fibers bearing load–longitudinal fibers breaking. | Shaolin Li Lehua Qi Ting Zhang Jiming Zhou Hejun Li | 2017 | Journal of Materials Science & Technology2017，33，6： | 2 |
| 6 | Modeling of transverse welds formation during liquid-solid extrusion directly following vacuum infiltration of magnesium matrix composite显示文摘Liquid-solid extrusion directly following vacuum infiltration(LSEVI)is an infiltration-extrusion integrated forming technique,and transverse weld between upper residual magnesium alloy and magnesium matrix composites is a common internal defect,which can severely reduce the yield of composite products.To improve current understanding on the mechanism of transverse welding phenomenon,a thermo-mechanical numerical model of LSEVI for magnesium matrix composites was developed.The formation of transverse weld during extrusion was visualized using finite element simulation method,and the formation mechanism was discussed from the aspect of velocity field using a point tracking technique.The simulation results were verified by the experimental results in term of weld shape. | Jian Liu Lehua Qi Haiyan Zhang Heping Hou | 2015 | Journal of Magnesium and Alloys2015，3，3： | 2 |
| 7 | A new kind of resin-based wet friction material:Non-woven fabrics with isotropic fiber networks as preforms显示文摘As an alternative to short fibers,non-woven fabrics(NWFs)were made using different types of long fibers to optimize the performance of paper-based friction materials and their technology.In this investigation,the fillers and resin were impregnated into these NWFs to prepare three kinds of wet friction material.The tribological,mechanical,and thermal properties of the new wet friction material were studied.The results indicate that the dynamic friction coefficient of the new friction material is approximately 0.12 and the static friction coefficient is approximately 0.15;the better wear rate is 0.81334×10^(-14)m^(3)·(N·m)^(-1).In addition,the temperature for 10%mass loss yielded 100°C enhancement and the tensile strength was improved by 200%,compared to previously reported values.Most importantly,the advantages include a simple preparation flow,low cost,and resource conservation.This is a promising approach for the future development of paper-based friction materials. | Yewei FU Le ZHOU Tao YIN Zhongyao LUO Hejin LI Lehua QI | 2021 | Friction2021，9，1： | 2 |
| 8 | Effect of Extrusion Forming on Compressive Strength of Al_(18)B_4O_(33)w/Mg Composites显示文摘The aluminum borate whisker reinforced magnesium matrix composites (Al18B4O33w/Mg) were fabricated by pressure infiltration technique and extrusion-vacuum infiltration technique respectively to study the effect of extrusion forming on their mechanical behaviors. The microstructure of the composites was observed by scanning electron microscopy. The compressive strength was investigated and compared with that of the matrix alloy AZ91D. The results show that the extrusion forming could cause fracture of the whisker, but reduce the holes in the composite during impregnation and improve the interfacial bonding between the whisker and the matrix alloy. Compared with that of the matrix as-cast alloy AZ91D, the compressive strength of Al18B4O33w/Mg by the pressure infiltration technique was increased by 22%, while that of Al18B4O33w/Mg by the extrusion-vacuum infiltration technique was increased by 120 %. | Li Zhengjia Li Hejun Qi Lehua Oy Haibo | 2009 | 稀有金属材料与工程2009，38，A03： | 2 |
| 9 | Wear behaviors of C f /Mg composites fabricated by extrusion directly following vacuum pressure infiltration technique显示文摘 | Lehua Qi Juntao Guan Jian Liu Jiming Zhou Xinliang Wei | 2013 | Wear (-)2013，，1： | 1 |
| 10 | Measurement of the extinction angle about laminar pyrocarbons by image analysis in reflection polarized light 显示文摘 | Li Miaoling Qi Lehua Li Heiun Xu Guozhong | 2007 | Materials Science and Engineering A2007，448，12： | 1 |
| 11 | Preparation of SnOz/C biomorphic materials by biotemplating from ramie fi- bers显示文摘 | HE Xinhai QI Lehua WANG Junbo | 2011 | Bull Mater Sci2011，34，5： | 1 |
| 12 | Research on prediction of the processing parameters of liquid extrusion by BP network显示文摘 | Qi Lehua | 1999 | Journal of Materials Processing Technology1999，95，： | 1 |
| 13 | Effects of the fiber orientation and fiber aspect ratio on the tensile strength of Csf Mg composites显示文摘 | Wenlong Tian Lehua Qi Jiming Zhou | 2014 | Computational Materials Science2014，89，6： | 1 |
| 14 | Journal of Materials Processing Technology显示文摘 | Li Hejun Luo Shoujing Qi Lehua | 1992 | 32:4891992，32，： | 1 |
| 15 | Research on the Neural Networks Used for Shaping Tubes by the Liquid Extrusion Process显示文摘 | Qi Lehua Li Hejun Hou Junjie | 2000 | Journal of Materials Engineering and Performance2000，9，： | 1 |
| 16 | Research on lateral instability of the uniform-charged droplet stream during droplet-based freeform fabrication 显示文摘 | LUO Jun QI Lehua ZHOU Jiming | 2008 | International Journal of Machine Tools and Manufacture2008，48，34： | 1 |
| 17 | Research on predictions of the processing parameters of liqud extrusion by BP network 显示文摘 | Qi Lehua Hou Junjie Cpuieiling | 1999 | Fuel1999，95，： | 1 |
| 18 | Manufacturing of micre thin - walled metal parts by micro - drnplet deposition 显示文摘 | Chao Yanpu Qi Lehua Xiao Yuan | 2012 | Journal of Mate- rials Processing Technology2012，212，2： | 1 |
| 19 | Fabrication of Short Carbon Fiber Reinforced AZ91D Alloy by Infiltration-Extrusion Integrated Technique显示文摘Short carbon fiber reinforced AZ91D alloy (Csf/AZ91D) was fabricated by the infiltration-extrusion method. The short carbon fiber preform was infiltrated with melted AZ91D alloy under the assistant of gas pressure. The extrusion processing was applied following the infiltration processing directly. The tensile property and microstructure of the Csf/AZ91D and that of the die-casting and extruded AZ91D alloy was compared. The results show that the short carbon fiber reinforced AZ91D alloy present excellent tensile property. The tensile strength and modulus of elasticity of Csf/AZ91D is about 50% and 18% higher than that of cast AZ91D alloy, respectively. The elongation to fracture of Csf/AZ91D is about 50% lower than that of AZ91D alloy. | Ouyang Haibo Li Hejun Qi Lehua Li Zhengjia Su Lizheng Wei Jianfeng | 2009 | 稀有金属材料与工程2009，38，A03： | 1 |
| 20 | Research on lateral instability of the uniform charged droplet stream during droplet based freeform fabrication显示文摘 | LUO Jun QI Lehua JIANG Xiaoshan | 2008 | International Join-hal of Machine Tools and Manufacture2008，48，34： | 1 |
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