Papers by Author: W. Li

Abstract: A reasonable finite element (FE) model of grinding temperature field has been developed on the basis of analysis of the transient temperature field， and three kinds of boundary conditions are loaded on the element of a moving heat source. The study, which is based on the finite element principle, has been carried out using the numerical simulation software ANSYS. Many results have been obtained including three dimensional temperature distribution map. The simulated results under different conditions show good agreement with the experimental results. With the comparison of the dry-grinding and wet-grinding, the result shows that the wet-grinding temperature with a proper grinding fluid is rather lower than the dry-grinding temperature. Finally, the variable coefficient of convective heat transfer and the different form heat source have been discussed in detail.

Abstract: This paper introduces a novel economical direct metal forming process, which combines of traditional plasma welding processes and layer manufacturing process to fabricate sound metal part. As high heat inputs during welding could affect parts surface quality, a CCD visual monitoring system was used to monitor the process. To avoid the interferer from plasma arc light, the spectrum of plasma arc was measured and analyzed, and a narrow band filter system was designed. The images of molten pool were analyzed, and a fuzzy-PID controller was used to control the molten pool size. Experimental results prove that using this system can improve parts surface quality.

Abstract: The functional materials such as sapphire, silicon wafer etc. are processed efficiently with ultra-smooth surface for the demand of the rapid development of the IC industry. The precise double sided polishing process is one of the main methods of getting the ultra-smooth surface for these materials. This paper introduces the structure and characteristic of the precise double sided polishing machine with a precise pressure control system equipped a new type electro-pneumatic digital servo valve. The works, such as machine design, development of the control system and optimization of process parameters etc. are carried out to meet the requirement of the precise double sided polishing machining process. This equipment has the characteristic of high machining precision and precise control capability, so it can be applied to the ultra-precise machining of the ultra-thin sapphire, silicon wafers etc.

Abstract: The presence of residual stress in aircraft aluminum components can give rise to distortion after machining. Excessive distortion may result in the rejection of a part or the need for costly and time-consuming rework prior to placement in service. The purpose of this research was to develop a methodology for the prediction of machining-induced distortions of residually stressed aircraft aluminum components. Numerical simulation results show that the magnitude of machining distortion is strongly related to the square root of Stain Energy Density W or Stress Range σ . The experimental results demonstrate good agreement with the predicted machining distortions of 7075T73 bulkheads. It included that the original residual stress in the blocks of aircraft aluminum component is one of key factors to cause machining distortion.

Abstract: This paper discussed the principle about the Electrical Discharge Truing(EDT) technique ,which applied in lapping machining process, including EDT status with different environment and machining conditions, and an EDT equipment on a lapping machine have been developed and used in the experiment of EDT. Then some experiments were carried out for verifying of the EDT effect with different EDT parameters such as electric voltage, EDT gap, and the EDT media. Finally, the efficient and precision EDT was achieved with the suitable EDT parameters.

Abstract: In this paper, some molding process parameters such as injection time, packing time, packing pressure and process temperature etc. were optimized by the Computer Aided Engineering (CAE) simulation (Moldex 3D) for injection molding of a plastic lens. Some experimental trials were carried out for verifying of the CAE simulation results with checking of the lens shrinkage and birefringence etc. as well. The results showed that, the recommended molding process parameters from CAE simulation and the actual experiments were almost the same, hence the CAE is a established tool based on the scientific approach to reduce experimental works, to identify critical parameters and to save substantial costs. Lately, a perfect plastic lens was gained by the Injection–Compression Molding process with the optimized process parameters by a CAE simulation.