Papers by Author: Yong Dai

Abstract: this paper relates to the following studies: The model of cutting depth distribution of grains of Multi-cell-disc was analyzed and established. The shape of the abrasive grit has been discussed and the abrasive grit shape model of unit-bold was simplified. The superficial characters of elastic elements were tested by Nano-indentation tests and the loading-displacement character of superficial abrasive particles during loading was gotten. By using probability and statistics, the model of cutting depth distribution of grains was obtained.

Abstract: In the process of grinding precision balls, the motion state of balls has an important influence on the efficiency and quality. However, the normal movement of balls will be damaged because of slipping, so it must be avoided. Besides, to process different materials of balls, it should use different processing parameters. This paper studies a numerical analysis on the kinematic characteristics of the motion of balls, analyzes processing parameters which impact the motion of balls during grinding and the difference of the motion state of bearing balls and resin balls. Study shows grinding pressure and plate speed have a great influence to the motion of balls during grinding.

Abstract: Series of simulation of planetary precise ball lapping modes are put forward in this article, which use solid abrasives to get a high lapping efficiency. In this case, it is very important to obtain a better quality especially a better uniformity. Based on the simulation. of this new lapping mode, it is found that the lapping trace are mainly influenced by the eccentric distance and other factors.

Abstract: This work aims to obtain fine surface of silicon wafer during precision and ultra precision machining, and presents a new method called semibonded abrasive machining. A semibonded abrasive grinding plate is used in the semibonded abrasive machining. Abrasive particle of 1000# Green SiC and bond named SSB are adopted in the manufacture of the plate. Four plates with different concentration of bond which are 1.5%, 2.5%, 3.5%, 4.5% respectively are made. The paper studies the effect of concentration of bond, the control parameters which include the lapping time, the load, and the rotating velocity of the plate on the surface roughness. Experimental results indicate each plate with different concentration of bond can obtain fine surface roughness. When the load or the rotating velocity increases, there is little effect on the surface roughness, but the material removal rate increases correspondingly. The initial roughness of the silicon wafer surface lapping by the plate could be improved from Ra 0.2μm to Ra 0.02μm in 9 min.

Abstract: Dual rotation plates lapping method can effectively solve the limitations of traditional ceramic ball machining methods. This paper focuses on the application of Taguchi method to optimize the technique parameters to lap ceramic ball. The main objective is to study impact degree of the process parameters (lapping load, lapping speed combination and slurry concentration). The results show that the experimental design based on Taguchi method can determine the optimum machining conditions which improve the surface quality and geometrical precision of ceramic ball.

Abstract: Polishing with Flotative Abrasive Balls(FABs) is a kind of soft contact polishing means， and the conventional polishing plate and pad are not needed in this case. The pressure of polishing is the flotage which is the upward force that a fluid exerts on the FABs, but the movement of work piece is similar to that in conventional polishing, the removal rate and quality of polishing is influenced by FAB and its flotage. An experiment device is built up and two kinds of FAB are designed and produced. Some primary experiments are carried out in order to investigate the influences of the size of FABs on the removal rate and surface roughness in polishing with FABs. It is found from the experiments that the grain size and the layers of FAB may have great influence on the removal rate of polishing; the surface roughness is mainly decided by the ball diameter and the layers of FAB. The results of experiments are discussed and analyzed, it indicates that the efficiency and quality depend on flotage and the number of active grains when the velocity of workpiece is assigned.

Abstract: Few existing systems can support the reuse of conceptual design knowledge due to the lack of satisfying modeling technologies. In the present study, we investigated the ontology-based modeling technologies and apply them to develop a framework of conceptual design knowledge management. The practicability and validity of our framework were then examined in a Construction Machinery Design Knowledge Management System.

Abstract: The grain size and its identity of abrasives are of high importance to obtain the damage-free and low roughness surfaces in traditional polishing processes. The undesirable scratches will appear on the surface of workpiece, if the grain size of abrasives is of high decentralization, or some abnormal larger grains or impurities are interfused in polishing process. And it is very difficult to polish curved surfaces. A new polishing technology, which is called as polishing with flotative abrasive balls, is put forward in this paper, in order to solve the problems mentioned above. Some primary experiments and theoretical analyses are carried out. It is found that the contact pressure between workpiece and abrasive grains may be easily controlled, as a result, the depth of cutting may also be easily controlled and it is not sensitive to the grain size of abrasives. The new technology may also be used in the polishing of curved surfaces.

Abstract: Cesium Lithium Borate (CsLiB6O10 or CLBO) is the most effective non-linear crystal which generates ultraviolet harmonics of the Nd:YAG fundamental laser wavelength. In order to enhance the damage threshold, low CLBO surface roughness, by ultra-precision machining, is needed. Because the CLBO crystal has easy hydroscopic reaction and micro scratches in machining, ultra-precise machining of the CLBO crystal is a difficult technical problem. In this paper, the new lapping slurry and polishing slurry are introduced. And the deliquescence degree of CLBO is fallen to lowest. A new working technology is also adopted. After rough polishing, the concentration of ultra-precision polishing slurry is increased properly. So does the ultra-precision polishing speed, and the wiping speed is faster than the deliquescence speed. The CLBO crystal surface roughness can achieve 1nm and keep the surface quality well.

Abstract: It is of high importance to avoid scratches in lapping process. A Grain Size Sensitivity (GSS) model is put forward in this paper. The GSS is a relative parameter which defines the relative change of the depth of cutting, influenced by the change of the size of grain powders, by which it is possible to evaluate quantificationally the capability of lapping machines in avoiding scratches. It is useful for designing and using lapping machines. The simulating of lapping processes based on GSS model is carried out. The transferring of error is also discussed and a new structure of lapping plate with spring cells developed by the authors is introduced.