| In the case of elastohydrodynamic lubrication,the viscosity of the lubricant may decrease with the thinning rate of the high shear strain rate and increase sharply with the increase of contact zone pressure.Lubricant can not be treated simply as Newtonian fluid.In order to improve lubrication performance,it is more and more common that synthetic oils,mineral oils and polymer blends,and greases are used for lubricants in today’s industrial field.And most of these lubricants are non-Newtonian fluids.Due to the nonlinearity of the constitutive equation of non-Newtonian fluids,the previous solution to the non-Newtonian fluid lubrication problem is very complicated and difficult.Even though it is solved by numerical method,it is sometimes difficult to find a solution of convergence for large nonlinear problems.Therefore,nonNewtonian fluid lubrication has always been a difficult problem in lubrication theory.In this paper,the non-Newtonian fluid was fabricated by thickener and water,and then the lubrication problem of the non-Newtonian fluid was discussed by using the pervasive lubrication equation.The main contents are as follows:1.A polyoxyethylene aqueous solution having non-Newtonian properties is prepared by using a water-soluble thickening agent,polyoxyethylene and water.In order to investigate the rhelogy and film forming properties,polyoxyethylene aqueous solutions with different mass concentrations were prepared.The results show that the polyoxyethylene aqueous solution has shear-thinning behavior.As the concentration increases,the viscosity of the solution gradually increases,and the non-Newtonian behavior is stronger.Subsequently,Ostwald model is used to fit rheological curve,the fitting result was very good and the constitutive equation was obtained.The experimental results of aqueous film forming performance show that the polyoxyethylene aqueous solution has good film forming properties.2.The pervasive lubrication equation is derived by velocity separation method.Taking the power function non-Newtonian fluid model as an example,the pervasive lubrication equation is used to obtain the power function non-Newtonian fluid lubrication equation.Constitutive equations and corresponding two-dimensional differential lubrication equations of several commonly used non-Newtonian fluid models are given.In order to solve the non-Newtonian fluid point contact elastohydrodynamic lubrication problem,the non-Newtonian fluid lubrication equation is obtained by using Ostwald constitutive equation.Effects of parameters such as rheological index,load and entrainment speed on the lubrication characteristics of point contact elastohydrodynamics under isothermal steady state conditions were studied.3.Experimental study on elastohydrodynamic lubrication of polyoxyethylene aqueous solution under different working conditions were conducted.And the film thickness distribution under point contact elastohydrodynamic lubrication was measured and calculated.The effect of entrainment velocity and load on the film thickness of non-Newtonian fluid lubrication were analyzed and discussed.Finally,the theoretical results of the central and minimum film thickness which were calculated by using Hamrock-Dowson formula are in good agreement with the experimental results.4.Tribological performance test of thickener aqueous solution.On the UMT friction and wear test machine,the antifriction and antiwear properties of polyoxyethylene aqueous solution were investigated under the circumstances of steel-aluminum friction pair and steel-steel friction pair.And the effect of concentration and load pairs on the friction coefficient were analyzed.Based on friction coefficient,the lubricating properties of the polyoxyethylene aqueous solution were studied.The results show that the lubricating performance of polyoxyethylene aqueous solution is better than that of pure water.In a certain load range,the friction coefficient,under the circumstances of steel-aluminum friction pair and steel-steel friction pair,decreases with the increase of load.When the load is constant,with the increase of the mass concentration of polyoxyethylene aqueous solution,the anti-friction performance of polyoxyethylene aqueous solution,under the circumstances of steel-aluminum friction pair and steel-steel friction pair,is improved. |
