| As development of technology and the higher requirement of users,complex curved surface,which consists of various radius curve surface area,is widely used in more and more products.How to obtain high quality complex curved surface with high efficiency and low cost has become a research focus.A novel shear thickening polishing?STP?based on the shear thickening effect of non-Newtonian fluid was proposed.A flexible“fixed abrasive tool”is formed to polish the workpiece surface efficiently.Own to the fluxility of the slurry,the“fixed abrasive tool”can match well with the complex curved surface with various curvature.As a result,a high efficient polishing can be expected for complex curved surface.High surface quality,high efficiency and low cost are expected to be achieved by this new polishing method.In this paper,the material removal mechanism and the shear thickening property of slurry was analyzed.The main contents are as followed:The shear thickening mechanism was explained.A shear thickening fluid composed of water and polyhydroxy compound particle was selected as the base fluid of slurry,and the prepare process was developed.The influence of abrasive material,abrasive grit size,concentration and temperature,on the rheological properties of shear thickening polishing slurry?STPS?was discussed.It is found that a good shear thickening property can be obtained with 50%dispersed particle in size of 5-15?m.The slurries with Al2O3 abrasives present a typical shear thickening curve,and the viscosity increased nearly 40 times when shear rate from 30 s-11 to 1000 s-1.Based on the constitutive equation of non-Newtonian fluid and empirical formula of hydromechanics,mechanical model calculation formula of surface forces in shear thickening polishing were deduced.The theoretically calculated values were compared with the measured values.The difference between the two results is in 9%.Based on the theory of wall slippage,the wall slippage of the polishing slurry was measured by rheometer,and the results provide further proof to explain the material removal mechanism in STP.According to the kinetics theory of abrasive,the force of particles in polishing slurry was analyzed.Based on the ratio of different size of abrasive and dispersed phase particles,abrasive-dispersed phase combination model was established.Based on the Hertz theory,material removal model of a single grain was setup,and then the mathematical model of material removal was obtained.The effects of polishing velocity,abrasive concentration and abrasive size on material removal rate were analyzed respectively.By single factor polishing processing experiment,the effects of the polishing speed,particle concentration and particle size on the polishing efficiency and quality were discussed.Through the orthogonal experiment analysis,it is concluded that,polishing speed,followed by abrasive concentration and particle size,has greatest influence on the polishing material removal rate and surface roughness.Through the orthogonal experiments,the optimized process parameters under the condition of this study were obtained,and the surface roughness decreased from Ra 125 nm to Ra 4.2 nm after 1 h shear thickening polishing. |
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