| Abrasive flow machining technology has many advantages, this makes it be one of the most widely used surface finishing processing methods. Since AFM technology appears, a lot of research work was done by experiment observation or analysis to get qualitative conclusions, however the progress is limited. There are many influence factors in abrasive flow machining, such as abrasive viscosity and elasticity, abrasive mixing rate and processing temperature, etc. Due to the role of the abrasive cutting, it can cause damage to the rheometer, and viscoelasticity of abrasive fluid is beyond the range of existing rheometer, so it is impossible to use expensive rheometer measurements to measure rheological parameters of abrasive media. If the abrasive viscoelastic and some important rheological parameters can’t be obtained, further research can not be carried out. Therefore, research and development of the new type rheological measuring device, abrasive viscoelastic test as well as research of rheological properties are very important. In the dessertation, the main work and conclusions are summarized as follows.Firstly, a depth discussion about the flow pattern of viscoelastic abrasive fluid in a circular pipe theoretical is made, the flow characteristics of the abrasive in the circular pipe three zones and the abrasive flow equations in the full exhibition flow area at cylindrical coordinates are derived. And based on non-newton fluid theory, the rheological properties of the abrasive fluid flowing in a circular pipe are obtained.Secondly, according to the theoretical analysis of abrasive flow characteristics, a rheological measuring device was designed, and a detail introduction to the test principle of the device was made. With the rheological measuring device and the capillary rheometer, a test of viscoelastic and rheological parameters of the same abrasive carrier was made; the test results were compared to verify the reliability of rheological test device.Thirdly, two kinds of abrasive media (1#、2#) with the same carrier and different particle sizes of abrasive were test by the rheological measuring device, and shear stress τw, shear rate γw, the apparent viscosity η, the first normal stress difference N1were obtained under three different temperature(25℃,35℃,45℃). Conclusions were drew through theoretical calculation and analysis: shear stress of abrasive media rises with shear rate increasing, but its apparent viscosity decreases; rheological index n of abrasive media is less than1and rises with temperature increasing, then it approaches to1; viscous coefficient K of abrasive media decreases with temperature increasing; the first normal stress difference of abrasive media rises with shear stress increasing and goes down with temperature increasing. The theoretical analysis verified abrasive media belongs to the pseudoplastic fluid of the non-newton fluid by the test conclusions. These all rheological parameters provide a reference for parameters selecting of abrasive flow machining and lay a theoretical foundation for further study.Lastly, based on the finite element analysis software Polyflow, the flow pattern of viscoelastic abrasive fluid in circular pipe is numerically simulated. In the case of changing the inlet flow rate, the change of the pressure distribution along the flow direction and velocity distribution along the radial direction under the different inlet flow rate are obtained by simulating the flow pattern of1#abrasive fluid. While in the case of changing apparent viscosity value of2#abrasive fluid, its flow pattern is numerically simulated in circular pipe, the change of pressure distribution along the flow direction under different apparent viscosity is obtained. The simulation results and the test results of the two abrasive fluid on rheological testing device is contrasted, verifying the rationality of the numerical simulation, and the conclusion can provide important reference basis for further study of AFM numerical simulation method. |
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