Tribological Performance And Experimental Study Of The Wheel/Workpiece Interface In MQL Grinding Using Nanofluids

Grinding is one of the important parts in modern machining.Because of grinding processes which has the high cutting speed,high energy consumption and bad working environment.In addition,grinding is the negative rake cutting of abrasive grains on wheel surface,so it appeared this phenomenon of larger friction,high temperature and high pressure.Therefore,the lubrication play a critical role in grinding processes.High speed relative friction motion between the grinding wheel and the workpiece two friction pairs,which need good lubrication to ensure the normal processing process.The lubricants have a significant effect in reducing the friction and wear,removing the chips and improving the service life of grinding wheel.It is also an important part of achieving good surface quality of workpiece and avoiding thermal damage.As a result of the growing need for environmental protection and the increasing number of health problems faced by workers,traditional lubricants are gradually being replaced.Nanofluid is one of lubricating fluid through add nanoparticles in the proper base fluid,which has the properties of high efficiency,environmental protection,low-carbon and cleaning.It not only improves the heat transfer ability of the grinding zone,but also increases the lubrication performance of the friction pairs.This dissertation includes systematic theoretical and experimental investigations on the discussion of minimum quantity lubrication?MQL?base oil,the selection of nanoparticles,the decision of optimum lubrication concentration of nanofluid,and the judgement of the processing performance match between different lubricants and workpieces.The main contents are as follows:1.The machining mechanism of MQL grinding is studied,and the mechanism of abrasive machining and the evaluation parameters of lubrication performance are explored.The mathematical model of grinding force was established by using micro sliding grinding force,and the grinding force,friction coefficient,specific grinding energy,G ratio and the micro topography of the workpiece surface and grinding wheel surface were used to characterize the lubrication performance.2.The effects of the physical and chemical properties?carbon chain length,molecular structure and fatty acid type?of different vegetable oils on the lubricating properties of the wheel/workpiece interface were investigated.The lubricating properties of seven typical vegetable oils as base oils were analyzed.The influence of different vegetable oils on the lubricating properties of the grinding zone was obtained.3.The influences of physical and chemical properties of different nanofluids on the lubrication characteristics between the wheel/workpiece interface were analyzed.In the experiment,six different nanoparticles were added in palm oil to prepare the nanofluids,and the lubrication performance of nanofluids was studied,and the influence of different nanofluids on the lubrication performance in grinding zone was obtained.4.Grinding experiments are used to evaluate the tribological properties of nanofluids,which are difficult to capture experimental phenomena and difficult to achieve.In order to study the tribological properties of the nanofluid in the film forming mechanism,the tribological properties of the nanofluids were studied by the tribological test.The results are compared with the results obtained in grinding experiments.5.The different concentrations of Al₂O₃ nanofluids have a significant influence on the tribological performance of the grinding wheel/workpiece interface.The nine different concentrations of Al₂O₃ nanofluid as lubricant were used.The influence rules of different concentrations of Al₂O₃ nanofluids on the lubrication performance of grinding zone were obtained.6.In order to optimize the processing and matching between different lubricants and different workpiece material,the Al₂O₃ nanofluid and MoS₂ nanofluid which have the better lubrication performance were used.The nickel base alloy 718,ductile cast iron and 45 steel as the workpiece material.The optimal MQL lubricants and workpiece materials machining match were determined through the orthogonal experimental design.The processing rules between different lubricants and different workpiece material are obtained.