Papers by Author: Yu Kui Wang

Abstract: In this paper, a simplified CNC system based on PLC and position controller is introduced. The position controller FX2N-20GM, is a pulse chain output unit, which can control motors to accomplish linear interpolation and circular interpolation. PLC,with the mode of FX_2N-16MR, the logic control unit of system, reads position data from the position controller and determines the operation of the system. Labwindows/CVI,the configuration software on PC, is the upper monitoring system, showing the motors position in real time by monitoring PLC. The system, combined PLC , position controller and configuration software, can draw any kinds of two dimensional graphics and show the trajectory of motors on PC in real time, the linear interpolation and circular interpolation had been perfectly implemented by a series of experiments. Compared with classic CNC system, it did not contain tedious hardware wring or complex software programming, which makes the whole structure a simplified CNC system.

Abstract: The material removal process of SiC/Al particulate (SiCp/Al) metal matrix composite by micro-wire electrical discharge machining (micro-WEDM) is influenced by many factors interaction, which makes the mathematical model of surface roughness (SR) be difficult to obtain effectively. To solve this problem, experimental study method is conducted under the constraint conditions. In this paper, a central composite design (CCD) testing with 3-factor and 5-level is carried out and SiCp/Al metal matrix composite machining test scheme is designed, and then second-order relational model is established between SR and main power parameters (open-circuit voltage, capacitance, and pulse duration) by using response surface methodology. Through multiple quadratic fitting, the quadratic regression mathematical model of SR is obtained. Constrains of actual machining condition upon the parameters are analyzed further. With the goal of reducing SR of SiCp/Al metal matrix composite by micro-WEDM, the parameters optimization model is established. Particle swarm optimization (PSO) algorithm and its procedure are designed to solve the model. Test proves that the algorithm could achieve optimized process parameters which satisfy multiple constraints rapidly and effectively.

Abstract: A new method for drilling micro-hole called EDM-ECM combined processing is proposed in this paper. This method consists of EDM shaping and ECM finishing, and they are carried out in sequence on the same machine tool with the same electrode but different dielectric medium. Micro-hole drilling experiment was done by micro-EDM, micro-ECM and EDM-ECM combined processing. The results show that the machining efficiency is improved by 9.2 times compared to conventional micro-ECM, and machining precision and shape accuracy of micro-hole are much better. The surface quality and mechanical property of the workpiece are improved, since the recast layer and surface defects generated by EDM are removed completely by ECM finishing. It proves that this combined machining method is possible and useful in the field of micro-hole drilling.

Abstract: The fabrication of a micro air journal bearing for micro gas turbine engine is investigated based on CAD/CAE and CAM in this paper. Numerical simulation of the aerodynamic micro air bearing is conducted to investigate the bearing load capacity. Then, a removal analysis and contouring strategy of accurate micro-WEDM processing for the air bearing is conducted based on CAM postprocessor. The extended and trimmed tool path is adopted for micro-WEDM. The inner and outer diameter of the bearing is 1.068mm and 1.165mm, respectively. The radius of the bearing corner is 15.9µm, and the height is 53µm.The satisfactory workpiece shape illustrates that the CAD/CAM integrated system is accurate and useful in micro-structures machining.

Abstract: In this paper electrochemical machining of micro slots using a shaped electrode instead of the traditional cylindrical electrode is presented. By applying shaped electrode the flow state of processing can be improved. An electrochemical machining (ECM system for meeting the requirements of the ECM process was established and a shaped electrode was fabricated by BEDG (Block Electrical Discharge Grinding). A set of experiments were carried out to investigate the influence of shaped electrode on machining efficiency and shape precision. The results show that the side gap and frontal gap of the micro slots can be reduced and machining speed will be improved when the shaped electrode was used compare with cylindrical electrode.

Abstract: A numerical model of cathode erosion in EDM process using finite element method is presented. Using this model, numerical simulation of the single spark of EDM process has been carried out with parameters such as conduction, convection, the latent heat of phase change, thermal properties of material with temperature and gauss distribution of heat flux to predict the temperature distribution in the discharge point of cathode as a result of single discharges in EDM process. The simulation result shows the trend of dynamic temperature distribution of heat -affected zone and well explains mechanism of material removal in EDM process.

Abstract: In this paper an electrochemical drilling method for machning micro holes using a flatted electrode instead of the traditional cylindrical electrode is presented. Both electrochemical drilling processes, in which the cylindrical electrode and the flatted electrode were used respectively, were introduced under same machining conditions. The taper of the micro holes between entrance and exit was reduced and machining speed was improved when the flatted electrode was used compare with cylindrical electrode. The flow field simulation was taken out to investigate the reasons for micro holes electrochemical drilling has advantage in taper reducing and machining speed increasing with flatted electrodes.

Abstract: A micro air journal bearing for micro gas turbine engine is designed in this paper. 2D simulation of the aerodynamic micro air bearing is conducted to investigate the effect of the main parameters of the air bearing on the load capacity, including the clearance between the air bearing and shaft, the gear number and height of the air journal bearing, the rotational speed of rotor. The optimum value of the important parameters are explored and presented. The time correlation method is used to solve the RANS (Reynolds Averaged Navier-Stokes) equations. Requirements both from load capacity and motion stability is considered and compromised for a better and stable performance of the air journal bearing. The shaft is stably rotated in a relatively low speed of 1.18×105rpm, which is much lower than other researches and can be achieved easily.

Abstract: In this paper, an elastic deformation of the axial foil hydrodynamic thrust bearing used in 100KW gas turbine generator is studied. The finite element model of the foil hydrodynamic thrust bearing was established using Solidworks and ANSYS. The foil hydrodynamic thrust bearing which considered foil deformation was analyzed and calculated based on the results of the approximate calculation. The FEA model considered the interaction of plane foil deformation and wave foil. The wave foil was not hypothesized as the linear distributed spring when set up the finite element model. The ANSYS results have demonstrated that the deformation of foil bearing designed based on the result of numerical calculation can meet the requirement of minimal film thickness of bearing lubricant layer.

Abstract: Aiming at machining deep micro-holes in titanium alloy, an experimental approach for EDM adopted a fuzzy control system was introduced. The fuzzy control system based on statistics of discharge states, that pulse interval and jumping height as control parameters, was self-developed. The suitable parameter for the deep micro-hole EDM process can be handily adjusted and modified in visual MATLAB fuzzy editor. A lot of experiments for titanium alloy micro-hole machining were performed on the EDM machine tool adopting the fuzzy control system. A titanium alloy deep micro-hole with 80μm in diameter and 15 in the ratio of depth-diameter is obtained. The process and results of experiments show that the process stability and efficiency be improved; due to the fuzzy control system and its suitable control parameters are applied.