Papers by Author: Dong Hui Wen

Abstract: CVD diamond has become the mainstream trend for the development of diamond. Its ultra precision machining is one of the key technologies for expanding the application of CVD diamond film. The efficient polishing method is studied, called accelerant polishing technology, which can lower the activation energy needed in diamond graphitization by the accelerant action of transition metal. It accelerates reaction rates of graphitization and promotes the implementation of diamond’s removal mechanism. Experimentation results indicate that the polishing method is one new type of precision polishing technology with low cost and high efficiency.

Abstract: This paper attempts to use a kind of smart material-magnetorheological fluid and magnetorheological jet polishing method to polish mould. Use self-preparation MR fluid conduct experiments on MR jet polishing setup which developed by ourselves. After polished by MR jet, surface roughness of the mould improved from 812nm to 88nm. The result shows that experiment and its setup are feasible.

Abstract: A three axis CNC milling machine was used for the cutting tests on the inclined surface of the 53HRC hardened steel, the hardened steel surface for the tests were keeping a inclined angle about 200 with the horizontal plane. According to the analysis of three axial milling force in the different milling strategies and different milling parameters, the effect of the different spindle speed and milling strategies for the cutting force was studied while the ball end finishing milling the hardened surface. The results of the tests were the good reaction for the rule of the cutting force which was changing with the spindle speed n and milling strategies, in addition, the results gave the reference of selecting optimum milling parameters of ball end finishing milling.

Abstract: In order to obtain a stable acoustic suspension field, it is essential to select a system of ultrasonic. This paper through Theoretical analysis of a system of ultrasonic, combine the condition of acoustic levitation polishing, to select the ultrasonic generator, ultrasonic transducer and the horn, to provides a good base for obtain a stable acoustic suspension field.

Abstract: Analytical and experimental identifications on the characteristics of the acceleration signal in high speed milling (HSM) process using ball end mill were studied. Three parts of harden steel with different hardness were assembled together, as opposed to the single harden steel in general HSM process. Dynamic model of ball end milling was established, tests with new and worn cutter were carried out respectively. Time domain analysis on the acceleration signal showed that the amplitude varies with the hardness through the whole cutting path. Furthermore, frequency domain analysis using fast Fourier transform (FFT) technique shows that the spectrum of the vibration signal using new cutter contain the tool spindle rotation speed as fundamental frequency and its harmonics. On the other hand, the spectrum of vibration signal under tool wear state contain other frequencies in addition to the fundamental frequency and harmonics, and this feature of spectrum can be used to monitor the state of the cutter during HSM.

Abstract: The purpose of this paper is to compare different simulation model of orthogonal cutting process using three different FEM commercial codes as well as with the results of orthogonal experiment. For one thing, element type, boundary condition and friction model between the chip and tool commercial have been compared when the numerical model established in implicit finite element code, Deform3D and the explicit code ANSYS/LS-DYNA and Thirdwave AdvantEdge. For another, main and thrust cutting forces, shear angles, chip thicknesses and contact lengths by three codes are compared with the orthogonal metal cutting experiment by Movahhedy and Altintas.

Abstract: Experimental research on the surface quality parameters such as roughness and removal rate in the precision lapping of sapphire was promoted in this paper, effects of processing parameters as load, speed of rotation, grain size and density on sapphire surface quality was studied by experiments. Results showed that lapping load and rotate speed were the most important factors on the removal rate, grain size played a key role in the removal rate and roughness under the same conditions, profile tolerance of surface shape depends on the flatness.

Abstract: Based on a novel polishing method named as acoustic levitation polishing. Analysis of the basic principles of acoustic levitation polishing. Through the simulation of fluid field in polishing, by the case that in a single or multiple sound source vibration, contrast the flow field of slurry. Analysis of the effect of the movement of slurry in the container to the surface uniformity.

Abstract: Proton exchange membrane fuel cell (PEMFC) has high power density and energy conversion efficiency. Bipolar plate is one of the key components of the proton exchange membrane fuel cell, not only affects the performance of the battery, but also affects the cost of the battery, which is become a bottlenecks. This paper introduces several common forms of the bipolar plate flow channel of the PEMFC, analyzes their advantages and disadvantages, and then some new type of flow channel type comes up after improvements on this basis, so the future development trend of fuel cells summed up is combined with bionics or using a complex flow field. An overview of the commonly used material and processing of the bipolar plate, respectively, graphite sheet, sheet metal and composite bipolar plates.

Abstract: This paper proposes a novel bipolar plate flow field of PEMFC with the intersectant microstructure. Numerical simulation about both the flow velocity distribution and the pressure distribution for the reactive gas were accomplished according to the model building by Pro/E, grid meshing and boundary condition specifying by Fluent. Compared to traditional serpentine flow fields, the gas pressure difference between the inlet and the outlet of this novel flow field is appropriate to promptly discharge the water produced during the operation of the PEMFC, and the flow velocity of the reactive gas among all the flow field is well-distributed, which assures reactions occurring uniformly in the flow field under the bipolar plate. All the properties of this novel flow field make a great sense to improve the integrated performance of the PEMFC.