Papers by Author: Ying Huai Dong

Abstract: A reversible machining method using micro electrical discharge machining (EDM) was developed. This new method can achieve depositing or selective removing of metal material for the fabrication of micro structures. It is easy to transform the machining process from deposition to removal in one EDM machining system. In micro EDM deposition process, brass, tungsten and steel material can be deposited successfully. The deposited material has compact fine texture and combines close to workpiece. Then, micro complex structures by series deposition strategy and sub-deposition strategy were deposited. In the selective removal process, the machining effects of different working mediums were researched. Results show that the machining effect in liquid medium is better than that of in air. Finally, using the micro reversible EDM process, a micro square column with 0.070mm in side length, 0.750mm in height and a micro cylinder with 0.140mm in diameter, 1.180mm in height were fabricated.

Abstract: The designing of a micro turbine for micro gas turbine engine is presented in this paper. Micro power system is becoming more and more important for micro- and nano-scale system. The fast development of MEMS (Micro Electromechanical Systems) has strongly enhanced the application of new harder work materials. The fabrication of metallic 3D microstructures has been one of the most attractive topics of micro machining. Currently the basic materials of Micro-turbine Engineering were nonmetal materials such as SiC, most of them are 2D or quasi-3D structures. As a low cost, flexible, good repeatable machining process with negligible process forces, micro-EDM milling is well suited for freeform metallic micro structures. A three-dimensional micro turbine was fabricated by micro-EDM milling. A major problem in micro-EDM milling of complex 3D structure by using micro-electrode is the electrode wear. For reducing the impact of electrode wear, A new CAM system based on the UG software platform is developed in order to get good accuracy 2and higher efficiency. A simple tool path generation by CAD/CAM software and a general electrode wear compensation strategy is presented. The wear compensation can be apart from the design of CAD/CAM systems, so existing common CAD/CAM systems can be used to generate milling tool path with an unequal thickness lamination. And then post process for wear compensation and EDM milling can be done to modify tool path by adding wear compensation. The micro turbine blades of which the material is nickel alloy (GH4169) were successfully fabricated by using this strategy. The diameters of turbine are 2.8mm, and the height of each blade is 0.4mm.

Abstract: The purpose of this paper is to study electrochemical micro machining (ECM) technology on stainless steel. The micro machining of stainless steel is difficult by electrochemical machining, especially in machining deep micro holes, because of an oxide layer formed on the surface. To machining stainless steel, HF is usually used in electrolyte to destabilize the oxide layer. In this paper, ECM of stainless steel by applying short pulses in less toxic and corrosive electrolyte is research. The influence of electrochemical machining parameters such as voltage, current, electrolyte composition to machine stainless steel was investigated. The results showed that the oxide layer can be reduced by adding chloride and complex.

Abstract: Based on the principle of micro electrical discharge machining (EDM), a reversible machining method is proposed, which can achieve depositing or removing selectively metal material for the fabrication of micro structures. It is easy to transform the machining process from deposition to removal in one machining system. The characteristics of the deposited material show that the components of deposited material are almost the same as those of the tool electrode, and the metallurgical bonding has formed on the interface between the deposited material and the base. Moreover, the deposited material has well machinability in different micro EDM selective removal process, including micro EDM die-sinking and micro EDM milling. As a result, a micro square column with 0.1mm in side length, 0.88mm in height and a micro cylinder with 0.14mm in diameter, 1.18mm in height were fabricated by using the micro reversible EDM process.

Abstract: This paper aims to investigate the performance of narrow beam machined by MWEDM. The narrow beam machining experiments are carried out on self-development Micro-WEDM with Φ30μm electrode wire. Narrow beams with the width around 10μm are machined on E52100 steel under different machine conditions (discharge energy, servo reference voltage). Based on the analysis of the experiments results, the coupled temperature and stress analysis using ANSYS finite element analysis software is performed to investigate causes of the failures on process.

Abstract: The dimension of micro turbine engine is usually only few millimeters, so the centrifugal structure is usually adopt. It must be designed by transonic speed for the higher single pressure ratio. The speed of the ration axis can reach 105r/min, so the gas bearing is adopt because the general rolling bearing is impossible. This paper designs a new wedge structure for the micro gas journal bearing. First the feasibility of this structure is verified by using the FLUENT software simulation. Comparing the simulation results with various parameters, finally major optimization parameters are confirmed.