Development For Lubricating Film Measurement In Conformal Contacts And Experimental Studies Of Lubricating Properties Of Simulated Synovial Fluids

Hydrodynamic lubrication is a basic lubrication mechanism of friction pair.Load-carrying capacity and friction are two important parameters in study of lubricationwhich are often used to evaluate lubricating properties. This topic has developed themeasurement technologies of load-carrying capacity and friction based on theslider-on-disc lubricating film test system. And these technologies are applied to thelubricating experimental study of biological lubricants. The main work includes:(1) A new method has been put forward to measure the load-carrying capacity oflubricating film. The measured film thickness versus speed curve was measured usingoptical interference technology under hydrodynamic lubrication condition in conformalcontacts. The load characteristic curve (dimensionless load-carrying capacity versusconvergence ratio) was got using dimensionless transformation. This method does notneed to adjust convergence ratio by manual and measure total pressure of fluid whichhas high measuring efficiency. Experiments show the new method proposed can be usedto evaluate the load-carrying capacity of lubricating film. The experimental results andclassical theoretical formula present the same trend. Even more important, theexperimental results show that the load-carrying capacity does not exclusively dependon the convergence ratio, which is different from the theoretical prediction. Theclassical theory needs to be revised.The interference levels easily loss in the measurement of high film thickness, so thestep speed measuring method has been used, and accuracy measurement has beendirectly achieved.The system was designed to measure the friction. The method of correcting was putforward to finish the accurate measurement of smaller friction under hydrodynamiclubrication. To transform the parameters based on the measured curve of film thicknessand speed, the friction coefficient versus the convergence ratio curve was got. Theexperimental curve and the theoretical curve present the same trend. The results showthat the dimensionless friction coefficient does not exclusively depend on theconvergence ratio, which is different from the theoretical prediction. The dimensionlessfriction coefficient is affected by the inclination and load factors.(2) The experiments have been carried out to study the fluid lubrication characteristics of water-based hyaluronic acid solution. It is shown hyaluronic acidaqueous solution has the good lubricating properties and load-carrying capacity. Underlow speed, high film thickness is got when inclination is small, which has referencesignificance to the design of artificial joint diameter clearance. It is shown hyaluronicacid aqueous solution has the shear thinning property by measuring the film thickness.A new technology was used to measure the rheological properties of hyaluronic acidaqueous solution under full-film lubrication. The measuring method of relative viscosityhas been proposed to evaluate the shear thinning property quantitatively.(3) The lubricating properties of protein aqueous solution have been studied byexperiments using the conformal contact measurement system. Protein adsorption onsteel slider surface has been observed online using optical interference images. Thesurface of slider was analyzed using scanning electron microscope, atomic forcemicroscope and surface profilometer. Two types of adsorption were found. One is acontinuous thin layer adsorption, and the other is discontinuous clusters. The other wascontinuous adsorption. A new approach based on optical film thickness formed with twodifference media was proposed to measure the thickness of the protein adsorption film.The formation of adsorption layer is affected by the shear rate and pressure. High shearrate and low load favored the growth of adsorbed film. The experimental results showthe existence of micro-corrosion on surface of the steel slider. And the micro-corrosionwas happened firstly in the inlet. It grew from the inlet to the outlet and promoted thegrowth of adsorption. The experimental results show that the micro-corrosion is affectedby the speed, load, and inclination.The multicomponent simulated synovial fluid has been preliminarily studied byexperiments. The protein adsorption layer and micro-corrosion is found on the surfaceof steel slider. What interested us is that the layer formation demonstrates positionselectivity.This topic developed measuring technologies of load-carrying capacity and frictionbased on the lubricating film measurement system of optical interference. The testsystem of conformal contacts has been improved for measurements of load-carryingcapacity and friction. Researches of simulated synovial fluid showed this system is suitable for study of the lubricating properties of biological synovia. It provides a newmethod for the research of bio-tribology.