Papers by Author: Zhong Ning Guo

Abstract: In this study, the 300 µm width micro-channel was manufactured by spray etching method. The surface roughness was analyzed by Laser scanning con-focal microscope. The relationship of the surface roughness and etching factor such as spray etching pressure, mask gap and time had been studied. The results show that the surface roughness increases initially, and then reduces with the size of mask gap. While the roughness increases as the spraying pressure increases. The etching time plays slightly effect on roughness for it has no impact on the etch uniformity as mask gap and spray pressure do.

Abstract: The NAK80 die steel was processed in spray etching with mask preprocessing.The effect of the mask gap width and etching depth on the undercut ratio was investigated . The result shows that with the increase of the mask gap width the effect of the etching depth on the undercut ratio increases. Based on the experiment, the relation of the mask gap width, the etching depth and the undercut ratio is obtained.

Abstract: PET-Ti composites have already been preliminarily used in the medical area due to the benefit of moderate biocompatibility of PET and the excellent mechanical properties of Ti. The connection of these materials always utilizes various technologies. Comparing to other methods, laser joining has the ability to achieve a clean weld and heat up materials in a spatially localized area only the material parts to be welded. This article describes how pulse shape, peak power and pulse-width affect the welding quality. And, make a conclusion that pulsed laser shapes, no matter with ramped-down waveform or ramped-up waveform, can be used to minimize the degradation of PET causes the decrease of gas bubbles that influence the bond strength and width.

Abstract: In this paper, the Lattice Boltzmann Method is applied to set up the numerical model of cavitations. The surface of the part is introduced into the symmetric bubble model to form the more realistic model called asymmetric bubble. With the help of simulation, no pulsation is detected but it is noticed that the pressure is no longer present uniform distribution for the four virtual surfaces symmetrically set around the bubble. The pressure close to the part’s surface is slightly higher and the velocity gradient is larger than those further away from the solid surface. And the distortion along the flow line is discovered at the end of the solid surface. The asymmetric bubble collapses in a complicated way thanks to the various velocities in different point of the bubble wall. What is more, a micro jet with radius of 10μm is generated which leads to the sharp reduction of momentum of the wall and the increase of the pressure near the bubble wall. According to the simulation, the impact on the work piece peaks at 1.6GPa.

Abstract: Applied in illumination area, high power LED (Light Emitting Diode) has a series of advantages with energy saving, environment-friendly, long life span, etc. However, the heat dissipation of the LED is a bottleneck in its development, and has become a key point which must be studied and solved urgently. In this paper, a typical LED lamp is modeled and thermal analysis has been performed using the software of Ansys.

Abstract: In this paper, an orthogonal experiment design method has been used to optimize the resistance microwelding (RMW) parameters for the fine copper wire and SUS304 stainless steel thin sheet welds. A L25(5⁶) orthogonal array for three factors (welding current, weld time and electrode force) with five levels was used. Joint breaking force (JBF) and surface appearance were selected as the index of evaluation. The results show that welding current was the most influencing parameter on both joint strength and surface appearance, and weld time had the next most significant effect. The orthogonal experiment design method was proved to be a promising technique to obtain the optimum conditions for RMW of fine copper wire.

Abstract: This paper makes some research on designing and manufacturing a nanosecond pulse power supply of electrochemical micromachining, including DC power supply, waveform generation circuit, rectifier and filter circuit，power amplification and rapid protection circuit. This power supply can generate 5MHz maximum frequency and square wave of 100ns pulse width, stably. The voltage ranges from 0V to 10V, and duty ratio ranges from 0.1 to 0.5, continuously.

Abstract: In hybrid process of electrolytic magnetic abrasive finishing (EMAF), there are usually two structures on the tool design, separated or composited. This paper has been focused on the design of the composite tool. How to make electrolyte reach working area is a problem which should be solved for the EMAF process when the composite tool is used, therefore a hollow structure of magnetic pole has been put forward as one possible solution. To understand the effects of the structure parameters of the tool on the abrasive brush of EMAF, Finite Element Method (FEM) has been employed to establish the magnetic field model and analyze the distribution of magnetic induction on the workpiece surface and magnetic pole.

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: Resistance microwelding of Au/Ni-plated phosphor bronze sheet to insulated Cu wire have been investigated using mechanical testing, optical microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The results show that mechanisms of joint formation involve solid-state bonding with Au and Cu atoms diffusion at low welding current, a combination of brazing and solid-state bonding at high welding current. Due to the hindrance of Ni plating which has a higher melting temperature and hardness, the joint breaking force is smaller than that without plating.