Papers by Author: Jian Cheng Fang

Abstract: According to analyzing the principle of atmospheric pressure plasma arc (APPA) cleaning metal surface, a model of heat and mass transfer is put forward with using transient-state heat transfer equation about interior heat source and Arrhenius equation of chemical reaction kinetics theory. With finite volume method, the one dimensional control differential equation is transformed into discrete control equation, which is calculated numerically and analyzed with the using of implicit scheme. Taken cleaning lubricant film as an example and analyzed temperature distribution of cleaning film on metal surface, the result indicates that the temperature of film has a strong effect on its removal rate which improves with increasing temperature. In order to both avoid damaging the workpiece surface owing to higher temperature and ensure removal rate of the film, there exists an appropriate temperature under given calculation conditions.

Abstract: The quality of coatings is directly influenced by the flattening and solidification of many individual molten droplets in plasma spray forming, so many properties such as thermal, electrical, mechanical etc are strongly linked to the real contact between the “piled-up” splats. The research on the transient temperature of impacting droplets and the heat transfer between droplets and substrate plays an important role in improving the quality of coatings. Because of complexity and high cost of temperature measurement systems for molten droplet during flattening in plasma spray forming at present, this paper presents a new kind of simulation measurement system for transient temperature of spray droplets when impacting on substrate based on LabVIEW, which could display the real-time changes of the temperature by waveform graph. Finally, the experiments were carried out on Pb-Sn alloy molten droplets to reveal the close connection between the impacting droplets temperature changes and the coatings quality, and the heat transfer between droplets and substrate was discussed.

Abstract: The main factors that influence the deposition efficiency and forming quality are the state of in-flight particles, which are directly effected by process parameter during plasma spray forming. In this study, plasma spraying of ZrO2 powder was employed according to the method of orthogonal experiments, and the relationship between spray parameters and characteristics of in-flight particles, which were monitored by an optical monitoring system of CCD camera, were investigated. Radial basis function (RBF) neural network model had been designed to forecast the temperature and velocity of in-flight particles, and optimized spray parameter. The comparison of the simulations with the experimental results shows the validity of the model.

Abstract: A novel technology of metal-ceramic parts with special functions formed by plasma spraying has become an important research trend. In this paper, the technical characteristics and spray parameters have been analyzed in detail based on the experiments of metal-ceramic near net forming, and some important techniques such as spray mould fabricating, backing and demoulding have been researched and summarized. Furthermore, the microstructure and property have been analyzed to forecast the quality of spray-formed parts. The research results show that plasma spraying is suitable for the production of metal-ceramic parts of any size with special mechanical and thermomechanical properties, which can realize the contemporary integration of forming and machining. Therefore, this technology with simple process and low cost is a method of metal-ceramic fabrication with a broad and brilliant prospect.

Abstract: To solve the difficult problem of selecting processing parameters of plasma arc cutting ceramic (PACC), the heat conduction model of PACC has been established and the calculating formulations of temperature field have been derived. Then, the distributions and influence factors, such as arc power, cutting speed and workpiece thickness, of temperature field of the ceramic plate and the anode plate have been studied. Based on the work above, the required arc power can be calculated. Moreover, the relation between thickness of ceramic plate and anode plate can be determined, which provides a helpful reference for selecting the thickness of additional anode plate.

Abstract: Magnetic field distribution (MFD) plays an important role in magnetic abrasive finishing (MAF). The mathematical models of the MFD in MAF have been established, and forced behavior of magnetic abrasive (MA) in the magnetic field has been analyzed in this paper. The MFD characteristics of the grooved poles have been numerically simulated, and the distribution law of magnetic force, interaction force and interface pressure have been investigated based on a single particle. The calculated results show that the MFD in the finishing zone is directly affected by the pole structure and working gap. The mapping function of interaction force and interface pressure corresponds to corner-effect in the peak point of the pole, and the magnetic brush stiffness is changed by the diameter and magnetization characteristics of MA, and the magnetic flux intensity (MFI). The numerical simulations are in a good agreement with the experiments. All of results mentioned above will offer an important method to study further on the finishing mechanism.

Abstract: Taking plate as the example, this paper studies the effect of tool’s shape and movement on the electrochemical as well as mechanical lapping characteristics in Electrochemical Abrasive Lapping (ECAL). It is assumed that the removal size of electrochemical action at a random point is in direct proportion to the electrical amperage through this point and the removal size of the lapping action is in direct proportion to the relative frictional distance. Based on the assumption above, electrochemical and mechanical lapping characteristics with different tools shape are studied theoretically. The results show that the diameter of the tool should be larger than the width of the workpiece when a discal tool is used and the inner diameter of the tool should be larger than the width of the workpiece when a ringed tool is used, on the other hand the ratio of the revolving radius of the tool to the diameter of the tool as larger as possible avails to improve the precision and so does the ratio of the angular velocity of the workpiece to the rotating angular velocity of the tool.

Abstract: Flexible forming using plasma arc (FFUPA) is a newly developed method of sheet metal forming. It makes the forming by means of thermal stress and thermal strain without mould and die, and is recognized as a promising forming method in developing new products. But the forming effect of FFUPA is determined by many factors, which compose a highly nonlinear system due to their complicated interact. As a result, it is difficult to predict the forming results and choose the processing parameters in FFUPA. In this paper, BP neural network is applied to solve this problem. After introducing the mechanism of FFUPA and analyzing the influence of processing parameters on the forming result, BP neural network is established, which include an input layer, an output layer and a hidden layer. When inputs and outputs are properly chosen, the BP neural network can be used to predict the forming results and to select the forming parameters. To verify the validity of this network, the results obtained by the BP neural network are compared to those obtained by experiments, and the results show that the former is close to the later, which indicates it is feasible to apply BP neural network in determining the processing parameters and forecasting the bending effects in FFUPA.