Papers by Author: Shi Ming Ji

Abstract: The soft abrasive flow machining was proposed for solving the problems of difficult contact finishing in course of mould manufacturing. It could reach the specular level and control turbulence abrasive flow. Based on the topological structure transformation of LSM, a two- dimensional model of the two-phase flow is established. This mechanics model with the SIMPLE (semi-implicit method for pressure-linked equations) algorithm incorporated is used to simulate the movement of the turbulent flow by using of k-ε model. The computed results show that this 2D model can preferably simulate the movement of the two-phase flow, and the characteristic parameters of abrasive two-phase flow are derived.

Abstract: Ceramic materials are widely used in the fields of aviation, chemical industry, military, machinery, electronics, so there are so many researches on ceramic materials. This article is mainly about ceramic sample preparation by polishing process for nano-indentation, taking Alumina ceramic and Zirconia ceramic for example. As we know, nano-indentation test is an effective mean to study materials. It is concluded that after polishing, the ceramic surface roughness can reach Ra<10nm and maximum scratches<1nm, flatness<1μm, we can get good quality surface, that well meets the surface requirements in nano-indentation.

Abstract: The fast development of SAW requests higher quality surface of CVD diamond films. Nowadays the mechanical lapping method is one important way to polish CVD diamond films, but the processing cost is high due to the low machining quality and efficiency. This paper reports a new accelerant lapping technology base on mechanical lapping and exploratory studies the role of three kinds of metal of the iron, titanium and nickel in the process of lapping. Firstly, ANSYS/LS_DYNA was used to simulate the process of friction and cutting between the CVD diamond films and abrasive plate of different material to analyze the temperature distributing on the interface and weather it is helpful for lapping. Then, experiment researches were carried out using the abrasive plate with different accelerant materials ratio. The results indicate that titanium is the most potent accelerant for polishing, followed by iron and then nickel. Experimental study also found that the accelerant lapping can carried out effectively by using the abrasive plate made of different metallic materials as accelerant to the diamond film grinding.

Abstract: Application of magnetic abrasive to the field of finishing processes is increasingly popular and important. Magnetic abrasive finishing (MAF) is effective in precision machining of non-planar workpieces. To study the control of working abrasive morphology and the valid way to solve “incline effect” which is common in some industrial field, application of magnetic abrasive in gasbag polishing is presented. Besides, the polishing system is introduced, and the important factors which influence the magnetic abrasive polishing are studied. Then some tentative experiments are carried out to study its polishing effect. It is found that the difference of surface roughness value and material removal rate under different bevel angle is in small range, which indicates this approach is useful in solving “incline effect”. The work in this paper is also a good attempt for further study that polish precipitous surface of mould or other products.

Abstract: The present work focuses on the numerical prediction of the manufacture quality of a sliding panel structure, in which the mobile components are floating on the immobile components and the 0.002mm thickness oil-film clearance between the mobile and immobile components. The interaction between them is the interfacial coupling interaction. A single-point spring-damping supporting element is introduced to simulate this type of interaction traditionally, in which the torsion of the mobile components is increasing with the supporting element reduced. To analogy the interfacial coupling interaction, the finite centrality supporting method is introduced to study the thin oil-film effect between the mobile and immobile components. And the manufacturing quality is predicting through the numerical study. Compared with the results derived from the numerical and experiments, the manufacturing error is in accordance with each other.

Abstract: Accelerant polishing is a new polishing technique based on the principle of diamond graphitization. It makes full use of the catalysis of transition metal such as Fe, Ti. In this paper, it researches on the trend of the graphitization of CVD diamond film at different temperature by DTA, TG, DTG and Raman spectra analysis. The results show that accelerant polishing technique can reduce the required conditions of graphitization, and carry out the graphitization reaction at a low temperature.

Abstract: Magnetorheological flexible gasbag polishing based on the special application of magnetorheological fluid (MRF) in robotic gasbag polishing technique is a novel efficient approach in the field of mould finishing. It can control the polishing pressure by changing the magnetic force generated by MRF inside of the gasbag with the effect of variable magnetic field of electromagnetic coil. Its mathematical model is established to study the main factors influencing the material removal. The orthogonal tests are applied to analyze these important parameters. From the experimental results, it can be seen that this new approach is desirable in realizing the control of surface figure accuracy and improvement of surface quality under certain condition.

Abstract: As far as the controllability of turbulence flow field surface effect of the soft abrasive flow was concerned, to begin with the analysis of the motion of the particle in the flow field, the paper studied the motion law of particle in the flow field, especially in the boundary layer. Based on the fluid-solid two-phase flow coupling style, it established the single particle dynamics model. Then it established the realizable k-ε model, in the light of the numerical simulation of turbulent flow. With the adoption of the computational method of SIMPLEC, it asked for the velocity and the pressure of fluid in the U-shaped flow passage, the velocity and the motion law of particles with different granularities and velocity, in the boundary layer. Experimentation results tell us that the original velocity plays a leading role in the motion trajectory of particles. The diameter influenced the particles motion trajectory in some degree.

Abstract: To improve the quality and efficiency of the finish, industrial robots are used to polish the workpiece cavities with complex shapes. This paper presents key technologies of robotic polishing system including path generation, tool orientation control and G-code converting. Robot path data is generated automatically from the NC data, and tool posture angle is superadded to the robotic polishing path according to the requirement of the robotic polishing technology. Specialized software is developed to automatically generate a program, which includes the path data and tool posture angle, and this program is uploaded to the robot controller for the die polishing process.

Abstract: According to liquid-solid two-phase flow model for the complexity of adaptation, as well as the impact of the concentration of particles, and we put forward a new method of considering the turbulent influence of particle concentration. Basing on the different turbulent control methods of the liquid-solid two-phase flow, we established the unified second-moment turbulence model. Using fluent software can realize turbulence model considering the particle pressure’s influence on particle’s concentration, and solve the problems of particle concentration and the flow passage control method. The simulation results showed that considering the concentration of particle’s influence on the pressure of the solid phase can accurately express the model of liquid-solid two-phase turbulent flow pattern.