Papers by Author: Yong Jun Zhang

Abstract: Planing-forming is a new process to machine fin heat sinks. This paper investigates the effects of the tool rake angle on the curved radius during planing-forming process by 2-D coupled thermo-mechanical finite element method and experiment verification. With the increasing of the tool rake angle from 0° to 30°, the curved radius increased. When the tool rake increased form 30°to 60°, the curved radius turned stable. After the chip displaced from the tool rake, the fin’s curling up due to the distribution gradient of the residual strain.

Abstract: Wire electrical discharge machining (Wire EDM) cutting of flexures for a rotary flexural bearing fabrication is developed. The results of FEA calculation and theoretical analysis show that one of the main factors affecting flexures’ machining is the weak torsional stiffness of the bearing cage, thus excessive deflections due to machining stress, heat generation and spark-induced vibrations may occur. To minimize flexure deflection during the machining process, a specially designed fixture is utilized. Other technical measures, including residual stress relief before and after Wire EDM cutting, reasonable cutting sequence planning, multiple-cutting (i.e., rough cut followed by several trim cuts) etc., are also adopted for cutting. Dimensional accuracy of ±5µm was obtained over the 150µm thickness for the bearing flexures, a variation of less than 3µm was achieved for the flexures of opposing sides, and surface roughness of better than Ra 0.3μm was obtained for the flexures of the entire bearing cage. These results show the validity of measures aforementioned.

Abstract: In view of major problems for the current metal cutting technology, a combined sand coated wire electrochemical machining technology is introduced. This method uses porous silicon carbide coated in metal wire electrode for grinding and electrolytic machining, which has both wire electrolytic and sand wire grinding characteristics, and greatly improves the cutting efficiency. The composite wire electrochemical cutting technology principle is analyzed. The method for determining the main process parameters is presented, and the effectiveness of its application in thin-walled metal pipe cutting is validated.

Abstract: Cellulosic Ethanol was considered to be the most promising alternative energy. For the biomass densification and pre-technical problems during the manufacturing process, we propose a new method concerning ultrasonic compression of cellulosic biomass, which does not need high-temperature steam heating, adding adhesive and high pressure, and it increases 60% of the fiber density and 20% of the sugar ratio through the grinding, ultrasonic compression molding and biomass briquetting.

Abstract: HVOF WC-Co spraying coating can enhance greatly the anti-wear performance of workpiece, but it is just the high hardness of spraying coatings that makes the polishing of workpiece very difficult, the application of HVOF was limited. In this paper, we discuss the feasibility of apply ECP(electrochemical polishing) to spraying coatings, include the study of electrolyte, the optimization of machining parameters et al., the experiment results show that it is not only feasible that apply ECP to machining spraying coatings, but also high machining efficiency, high quality surface can be obtained. The surface roughness can be reduced from Ra=4.0μm to Ra=0.7μm with suitable machining parameters during a very short time.

Abstract: For the theory and feature of EDM notching, the actual situation thermal model was established; by finite element method, EDM notch process base on killing and activating elements was successfully simulated, thermal and stress after notching was analyzed, while the conditions and mechanism of cracks generation was discussed.

Abstract: In order to resolve the problem of polishing micro-shafts and cavities, a novel technique of Micro-Electrochemical Polishing Mixed with Powder (EPMP) has been presented in this paper. That can be accomplished through high speed spindle driving micro-abrasive to proceed soft-grinding, which can achieve merit of little polishing force. The principle of EPMP has been introduced, and a series of issues have been studied. Finally, experiments of EPMP have been carried out based on above optimized machining parameters, and a micro-screw-shaft of Φ100μm has been polished. Which is near to mirror effect (Ra=0.02μm).

Abstract: In order to obtain well work performance, a new design process and the optimal method are systemically presented during ultrasonic vibrator’s design. Firstly, the general dimensions are calculated according to formula of ultrasonic theory. Secondly, 3D model without flange is established, and the best position setting a flange has been conformed through finite element analysis (FEM). Then constraints are laid on the flange, and the best model of vibration is obtained based on model analysis. The results are benefit to the following control design of ultrasonic vibrator. Finally, an ultrasonic vibration system has been made, and a series of experiments validate the feasibility of the design method.

Abstract: In order to resolve the problem of connecting rod notches machining, a new process of WEDM (Wire Electric Discharge Machine) has been presented, and it is greatly possible that expensive laser process can be replaced by WEDM in virtue of its unique advantages. Firstly, process parameters of notch have been analyzed, and project of machining notch using WEDM has been introduced, including measures to achieve good-quality notch. The relationship between cutting speed and power supply parameters has been investigated, and it is discovered that micro-crackle on bottom of notch are greatly effect to fracture splitting process, also new idea of active controlling micro-crackle has been presented. Finally, fracture splitting machining has been carried out. The cost and entrance standard of fracture splitting process are greatly dropped owing to new breakthrough of machining notch using WEDM.

Abstract: A system of ultrasonic combined with grinding has been designed, and one novel connective method of straight screw combined with taper surface has been applied in spindle, so compact size and high revolving accuracy can be achieved. Modal analysis of ultrasonic vibration system has been implemented by FEM (Finite Element Method), and its optimal dimension has been calculated to find out optimal vibration estate. Full-bridge converter has been applied in driving circuit of ultrasonic vibrator, and auto-frequency tracking has been designed in order that ultrasonic vibration works on resonant or quasi-resonant frequency. Finally, machining experiments have been fulfilled about ultrasonic combined with grinding, and its machining effect has been distinctly improved comparing ordinary grinding machining.