Abstract: The key question in the ice fixed abrasives (IFA) polishing is how to keep suitable ambient temperature in production process in order to avoid premature failure of the IFA. Based on above, the three dimensions finite element analysis (FEA) model of IFA polishing temperature field is built up at first. Then, the model reliability is demonstrated by experiments. Effects of ambient temperature and polishing time on temperature distribution and melting rate of the IFA pad are researched. The results show that the ambient temperature should be kept at about 10 °C in order to control the melting rate of the IFA pad effectively and keep longer polishing time. All the results provide the basis for choosing suitable ambient temperature in polishing.
Abstract: Three NiCoCrAlY coatings strengthened by different contents of nano-SiCp (nanometric SiC particles)were prepared on Ni-based superalloy substrates using crosscurrent CO2 laser, and the thermal shock test of these coatings was conducted by cycling between 1050°C and room temperature (10-15°C). The spalled area in the oxide scale of coatings after 10 thermal shock cycles and the thermal shock cracks in the cross-section of coatings after 100 thermal shock cycles were investigated using SEM, OM, and other means. The results show that the thermal shock resistances of NiCoCrAlY coatings are improved after adding nano-SiCp. Among nano-SiCp-added coatings, the coating added with 1.0 wt% nano-SiCp performs best. After 10 thermal shock cycles, there is a slight spallation whose area is only 2.65% in the oxide scale of the coating; after 100 thermal shock cycles, no internal crack is observed in the cross-section, and the amount and size of propagating cracks are slight.
Abstract: According to the characteristics of aerospace product, the model representation and storage of the rigid part and cable harness is proposed. The Dendritic Correlative Model of Mixed Assembly of Rigid and Flexible Parts (DCMMA-RFP) is introduced based on the hierarchical model and graph model. The assembly model which realizes the lightweight storage can clearly represent the hierarchy relation and assembly process of aerospace products. The assembly modeling process in the virtual assembly environment is detailed described. Finally the effectiveness of DCMMA-RFP is verified by an example.
Abstract: The heat source model and the heat input model were built by analyzing welding process. The rationalities of model were verified by finite element simulation. The method of prestressed welding was employed in order to reduce welding residual stress. The welding residual stress would be widely impacted by imposed prestress of 90% yield strength welding. At the same time the propagation of welding heat cracking in the heat-affected zone was properly controlled by prestressed welding.
Abstract: The swelling ratio and the pencil hardness of pad were introduced to evaluate the properties of hydrophilic fixed abrasive (FA) pad. The effect of pad composition on its swelling ratio and pencil hardness was studied. Results show that the swelling ratio increases with the rise of content of Trimethylopropane Triacrylate (TMPTA) and Urethane Acrylate (PUA) and the pad gets harder while there is more TMPTA and less PUA. Results also show that a low swelling ratio corresponds to a high material removal rate (MRR), and a low wet pencil hardness to a low surface roughness in each group.
Abstract: The thermal blockage and thermal round flow in HFCVD system for CVD diamond growth will lead to un-stability of product quality. Finite element method has been used to simulate the gas flow field around the cutting tool substrate within a HFCVD diamond reactor. Experiments have been done to prove the simulation results. Excellent agreement between simulation and experiment was obtained by depositing of CVD diamond coated cutting tool. The thermal blockage and thermal round flow in HFCVD system decrease by using a hollow substrate holder. High quality CVD diamond coating can be obtained using a hollow substrate holder.
Abstract: The experimental research on silicon was reported in this paper. The surface roughness under the different workpiece feed speed and linear velocity of the wire saws is studied mainly in this experiment. The effects of the workpiece feed Vs and the linear velocity of the wire saws Vw were analyzed.
Abstract: Firstly, taking the stability of the forestay bar as the restraint, the section area of the forestay bar was optimized from 1800 mm2 to 1178 mm2, with reduced weight of 16.1%. Secondly, the equivalent load of the forestay bar was obtained by using dynamics simulation software. Finally, the stress field and the fatigue life of the forestay bar were simulated. The results show that stress of the forestay bar with 929MPa can meet the requirement for its material strength, and fatigue life of 51200 times also satisfies the request of the nose landing gear. That is, material property of the forestay bar is utilized more than before, and its weight decreased successfully.
Abstract: The anisotropy of LBO crystal leads to the different properties of different crystal faces, such as thermal expansion coefficient, which results in trouble of ultra-precision machining. Chemical mechanical polishing of a face (001), b face (010) and c face (001) of LBO crystal by adopting Logitech PM5 Precision Lapping & Polishing Machine in the same process conditions was investigated. The effect of anisotropy on MRR and surface roughness was studied. In the same CMP process conditions, c face of LBO crystal is the highest MRR, b face is inferior to and a face is the lowest. And surface roughness of c face is the best, b face is followed and a face is the worst. The results also show that the anisotropy leads to the different MRR and surface roughness on different crystal faces. In CMP of LBO crystal, the higher MRR is, and the better surface roughness is in the scope of experiment.
Abstract: Micro-nanocrystalline diamond (M-NCD) Film may be successfully prepared on Mo substrate with DC arc plasmas jet deposition device. This paper studies the influences of carbon source concentration on the shape of M-NCD Film particles under circumstances of stable electric arc, and characterizes the grain size and quality of samples through SEM, AFM and Raman spectrum. The research result shows that, in the state of stable electric arc, relatively low carbon source concentration (1%) could deposit high-quality microcrystalline diamond film on the substrate, with a growth rate of up to 8.3μm/h and grain size of about 2～4μm; relatively high carbon source concentration (10% or 15%) could deposit high-quality nanocrystalline diamond(NCD) film on the microcrystalline diamond film at high speed, with a growth rate of up to above 12.6μm/h or 19.7μm/h, grain size of about 4～80nm and average grain size of 27.4nm.