Papers by Author: Qiao Ling Yuan

Abstract: As it was difficult to solve the near wall characteristics of flow field in softness abrasive flow machining (SAFM) on mould structural surface, a method for simulation the flow characteristics based on the low Re number k-ε model was proposed in this paper. The U-shaped tube was used as specific simulation object. The motion law of particles and related parameters were calculated and the precision machining mechanism of SAFM was discussed. Simulation results show that the micro cutting of abrasive flow mainly appears as the transposition of cutting location influenced by the particle pressure, and as the variation of machining efficiency influenced by near-wall particle velocity. Thus via control of the inlet velocity and its corresponding machining time, it is supposed to work out the machining process according with the machining requirements. By tracking near-wall particles, it can be confirm that the movement of near-wall abrasive particles is similar to stream-wise vortices. The cutting traces on workpiece surfaces assume disorderly arrangement, so the feasibility of SAFM method can be reaffirmed.

Abstract: Damping in built-up structures is often caused by energy dissipation or energy loss due to micro-slip along frictional interfaces interaction, which provides a beneficial damping mechanism and plays an important role in the dynamics vibration behavior of such structures, especially the contact stiffness and damping coefficient accounting for the kinematics joint. A detailed study the mechanics derived from the interaction interface between the different components has some embarrassment. And a careful study on the micro-slip phenomenon has been carried out using the finite element method. A classical joint configuration, the plane translation joint, has been used as the model problems. The focus of this paper is to evaluate the effect of dry friction coefficient, the external mechanics on the damping response of frictional joint interfaces interaction, to understand the evolution of the slip-stick regions along a joint interface during loading, and to quantify the amount of energy dissipation/loss during cyclic loading and its dependence on structural and loading parameters.

Abstract: This paper focuses on the dynamics characteristic difference on the two kinds of broading machine, the workpiece moving and the cutting-tool moving. There is 0.002mm thickness of oil-film clearance between the mobile and immobile components of the broading machine. Hydraulic pressure derived from the driving oil cylinder drives the workpiece or cutting-tool moving, while the material on the workpiece is cutting. Cutting-tool of the machine is an external expand cutter with the groove for breaking the cutting waste, the manufacturing phase is a pulse impact cutting exciting applying on the broading machine correspondingly. On manufacturing, natural characteristic of the broading machine is approximately the pulse impulsion frequency of the machine;response amplitude of the lather is increasing manifesting. The study is focused on the dynamics characteristic of two kinds of broading machine, the difference is workpiece or cutter moving, to predict the manufacturing performance.

Abstract: As it was difficult to solve the near wall characteristics of flow field in softness abrasive flow machining (SAFM) on mould structural surface, a method for simulation the flow characteristics based on the low Re number k-ε model was proposed in this paper. The greater curvature of small size tube was used as specific simulation object. The motion law of particles and related parameters were calculated and the precision machining mechanism of SAFM was discussed. Simulation results show that the micro cutting of abrasive flow mainly appears as the transposition of cutting location influenced by the particle pressure, and as the variation of machining efficiency influenced by near-wall particle velocity. Thus via control of the inlet velocity and its corresponding machining time, it is supposed to work out the machining process according with the machining requirements. By tracking near-wall particles, it can be confirm that the movement of near-wall abrasive particles is similar to stream-wise vortices. The cutting traces on workpiece surfaces assume disorderly arrangement, so the feasibility of SAFM method can be reaffirmed.

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: 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: 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: 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.

Abstract: Combining the advantages of rheological behavior of magnetorheological fluid (MRF) and flexibility adjustability of rubber gasbag, a magnetorheological flexible gasbag polishing technique applied to free-form mould is proposed. With the development of robotic gasbag polishing technique, the flexibility of rubber gasbag can be adjusted by three methods of changing its internal pressure controlled through a pressure control unit, its own material property and structural parameter, and the rheological behavior of MRF inside of it in response to the application of an alterable magnetic field. Effect of rheological behavior to the flexibility of rubber gasbag and surface quality of mould is the single most important focus in this paper. The magnetorheological flexible gasbag polishing system is established and rheological behavior of MRF with magnetic field is described. Through polishing experiment focusing on the relationship between the surface roughness and current around electromagnetic coil, it can be obtained that magnetorheological flexible gasbag polishing technique is effective to improve surface quality when increasing current around coil in certain extent.