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In order to study the performance of abrasive flow polishing on the micro-holes, the polishing process of abrasive flow with different abrasive particle sizes was carried out by using computational fluid dynamics. The distribution of fluid turbulence intensity and abrasive particle velocity, fluid turbulence dissipation rate and kinetic energy of abrasive particles were obtained and analyzed. The simulation reveal that the material removal rate is proportional to the size of abrasive particle size, while the surface quality is inversely proportional to it. Therefore, the appropriate size of abrasive particle should be selected according to the initial surface roughness of the workpiece. The research results have certain guiding significance for practical production.

In order to study the effect of different inlet velocity on the polishing quality of abrasive flow machining, this paper takes the variable diameter pipe as an example. The fluid dynamic pressure and total energy of abrasive particles under coupling field with different inlet velocities were carried out by using computational fluid dynamics software. The results of numerical analysis show that the polishing quality becomes better with the increase of the inlet velocity. At the same inlet velocity, the smaller the pipe diameter is, the higher the polishing quality will be. Therefore, the optimum inlet velocity can be selected by numerical simulation according to the size of the aperture of workpiece in the actual processing, which can provide technical support for the production.

Abrasive flow machining technology is a new type of precision machining technology. Due to its unique rheological properties, it can process any complex structure and size parts to meet the requirements that conventional machining cannot meet. Combined with the turbulent flow characteristics of the abrasive flow, the large eddy simulation numerical method is used to simulate the machining process of the abrasive flow. The influence of different sub-grid scale models on the simulation results is discussed. Taking curved tube as the research object, the static pressure, dynamic pressure and velocity of different sub-grid models are analyzed to find the best sub-grid scale model. Large eddy simulation method is used to simulate the complex flow channel parts, and the best sub-grid scale model suitable for complex flow channels is determined, which reveals the grinding and polishing rule of abrasive flow and provides academic support for future research. Therefore, it has frontier and important research value.

Based on the numerical analysis model of abrasive flow polishing, the effects of fluid turbulent kinetic energy, turbulent intensity and turbulent viscosity on the quality of polishing on polishing quality are studied and analyzed by taking variable diameter pipe as an example. The results of numerical simulation show that the polishing quality becomes better with the decrease of aperture. Therefore, the optimal processing parameters can be simulated according to the specific size of the workpiece, which can provide technical support for the production.

In order to analyze the effect of strain rate under tensile load on microcrack growth in Alpha Titanium, molecular dynamics simulation was used to analyze the results of atomic location, dislocation distribution, lattice phase transition, potential energy distribution and volume strain distribution. It was found that the cracks gradually evolved into holes after unstable propagation, and the holes were occupied by clusters on both sides of the material in the later stage under the necking of the material. The higher the tensile strain rate, the earlier the crack initiation and the larger the evolution of the through-hole. When the same strain value is reached, the lattice transformation ratio is higher under high strain rate loading. HCP is transformed into amorphous structure, BCC lattice type and a small amount of FCC type. Moreover, the larger the strain rate, the less the compatible deformation ability of the lattice is, and the more twins are produced. In addition, it is found that there are volumetric strain wave emission and diffusion in the model at the moment of void birth, and voids play a role in dividing the energy absorption region. Dislocation emission occurs at the crack tip and energy competition exists between dislocation and crack propagation.

In order to study the polishing quality of abrasive flow, The FLUENT15.0 software is used as the platform, taking the way that LES (Large-eddy simulation) model is combined with the Mixture model, the numerical simulation of Grain Flow Processing was carried out by regarding the servo valve nozzle as the research object. The results turn out that with the increase of the inlet speed, the flow state of the abrasive flow is more disorderly, and there is a dramatically improvement in dynamic pressure, which indicates that the collision and friction between the abrasive grains and the wall is more intense. In addition, the vortices and turbulence are more apparent, which are conducive to improving the polishing efficiency of abrasive flow so that achieve precision machining.

In order to solve the problem that the inner surface of heterosexual surface parts is difficult to be machined, a solid-liquid two-phase abrasive flow machining method is proposed. The standard model and the pressure-coupled SIMPLEC algorithm are used. The dynamic characteristics of the dynamic pressure, turbulent kinetic energy and turbulence intensity of the polygonal spiral surface flow channel were obtained by numerical analysis of the solid-liquid two-phase abrasive grain polished polygonal spiral curved pipe under different outlet pressure conditions. The numerical simulation results show that the grinding effect is inversely proportional to the outlet pressure. We can achieve better polishing effect by appropriately reducing the outlet pressure.

In order to study the numerical simulation of abrasive flow polishing small hole parts, the servo valve spool double nozzle parts were used as the research object, and the solid-liquid two-phase abrasive flow were used for numerical simulation, getting the dynamic pressure, velocity cloud and turbulent kinetic energy of the abrasive flow are obtained at different inlet velocities. Through the comparative analysis, the effect of the process parameters on the effect of the abrasive flow polishing small hole parts was obtained, which can provide a theoretical basis for the continuous improvement of the ultra-precision machining technology to promote the abrasive flow, so that the fatigue strength of the workpiece is improved, the reliability of the workpiece is enhanced and its service life is prolonged.

In order to obtain high quality of special channel surface and improve overall performance of machine or parts, this paper regarded the non linear tube-nozzle as the research object, and the single factor experiment was performed in the critical process parameter of abrasive flow machining(AFM) with self-developed abrasive medium, to study the relationship between process parameters and channel surface of microstructure and the influence of process parameters on the workpiece surface quality. The results show that abrasive flow technology can obviously improve surface quality of the non-linear tube, and has important practical value to improve the stability and the functional performance of the non-linear tube. The results can provide technical support for the deep research in the theory of abrasive flow machining.

The non-linear tube is widely used in military and civil fields and the general performance of the machine depends on the internal channel surface quality of it. The effective ways to improving the surface quality is solid-liquid two-phase abrasive flow polishing technology. So, the numerical analysis about the internal channel of non-linear tube polished by abrasive flow is implemented to analyze the effect of viscosity-temperature characteristics of abrasive flow polishing on the internal channel surface quality. Turbulent kinetic energy, intensity and viscosity, nephogram of the dynamic pressure distribution, and corresponding relation of temperature and turbulent kinetic energy, near the wall of non-linear tube, are received from the simulation in different initial turbulent kinetic energy and temperature which provides a theoretical basis for controlling the surface quality.

In order to solve the problem that the aperture of the small hole part is too small and the irregular shape of the surface is difficult to be processed. A solid - liquid two - phase abrasive grain polishing method is proposed. Based on the standard model and SIMPLEC algorithm, the numerical simulation of the surface of the micro – holes were carried out under different inlet speed conditions. The change of the turbulence kinetic energy, dynamic pressure and turbulence intensity of the micro – holes flow channel with the inlet velocity is discussed. The quality control law of the inlet velocity on the sol-id-liquid two-phase abrasive flow polishing. In order to verify the accuracy of the numerical analysis, the necessary solid-liquid two-phase flow polishing test was carried out with the micro-hole parts. The surface roughness of the inner surface of the micro-holes before and after polishing was tested. The results show that the surface roughness is reduced from 1.702 before polishing to 0.303 after polishing. The solid - liquid two - phase abrasive flow machining can effectively improve the surface quality of micro – holes.