| Ultrasonic Vibration Cylindrical Honing(UVCH),which is proposed based on the traditional honing,is a precision machining technology for further improving the cylindrical surface quality.In UVCH process,the oilstone is employed with mechanical vibration with constant high amplitude and high frequency.A large amount of honing heat is created because of the effect of honing pressure between oilstone and workpiece,which results in the temperature rise in honing grinding area.So,the quality of workpiece will be damaged.At present,though many fundamental research attempts have been seen to deal with model building and the grinding temperature measuring for traditional grinding machining,but it is also rare based on the background of ultrasonic vibration honing.The cavitation effect is a common phenomenon in the grinding area.The cavitation bubble grows in the honing grinding area and swells until it collapses.The bubble vibrates in the grinding zone subjected to ultrasonic vibration,and it gathers a lot of high temperature and high pressure energy in this process and frees by bubble collapse.The energy can form thermal damage to grinding zone especially the workpiece surface,and even create the micro-pit.The research for cavitation bubble is mainly focus on the bubble dynamics now,and the study of cavitation bubble thermodynamics is still relatively less.Therefore,this paper prepares to study the ultrasonic vibration cylindrical honing thermal and bubble thermal dynamics from the ultrasonic honing mechanism,the thermal model theory,bubble dynamics and thermodynamic equilibrium principle.The main work is described in the following aspects:(1)The UVCH basic mechanism is discussed.According to the grinding effect of the abrasive grains on the workpiece,the contact length between the abrasive grains and workpiece is deduced.The characteristics of reciprocating and rotating motion of the oilstone are combined,and the compound movement is considered during the calculation process.It reveals the friction relationship between the honing abrasives and workpiece from microscopic mechanism.(2)The model of temperature field and heat distribution under UVCH grinding zone are established.Based on the special machining technology of UVCH,it is different from grinding contact length between honing oilstone and workpiece and honing working time compared with traditional grinding.According to the traditional heat model theory,the heat model of UVCH grinding zone is established due to the logarithmic heat source distribution.The honing heat is produced in honing grinding area in honing machining.Grinding heat is distributed to grinding area by a certain proportion,mainly to workpiece,grinding wheel,grinding liquid and debris.The distribution form is changed because of the cavitation in grinding zone,and a new model is established considering the cavitation.(3)The heat distribution model and grinding temperature field are calculated.In heat distribution model,it is affected by several grinding parameters and honing parameters.Firstly,the effect of different grinding parameters to other relative is calculated.Then the influence of honing parameter on heat into the cavitation bubble is analyzed.The honing heat proportion into cavitation bubble is increased by enlarging of the ultrasonic spindle speed,ultrasonic vibration amplitude and honing depth,but the increasing amplitude and trend is distinguish.When the ultrasonic frequency,oilstone reciprocating speed and honing pressure gradually enlarged,the incoming cavitation bubble honing heat ratio is gradually decreased.From the moving trend,the grinding temperature shows an upward trend under every honing parameter,but it has different amplitude in a certain value.In addition,the temperature maybe has a rebound trend when it rises to a certain extent for some parameter groups because of the short honing time.In all honing parameters,the effect of ultrasonic vibration amplitude is special,and the temperature does not show a regular change trend.But in the overall process of changing,the grinding temperature of honing always remains in a certain range,the minimum is 350 K and the maximum is about 1000 K.(4)The dynamics and the collapsed temperature of single cavitation bubble which is produced in the grinding area in the UVCH were studied.In grinding zone,it has a series of dynamic behaviors.Under the different honing processing parameters,the cavitation bubble would have different vibration forms and vibration amplitude,and the dynamic model of single cavitation bubble was established in this paper.The influence of each honing parameter on the radius of motion of cavitation bubble is calculated by numerical calculation.The results show that the cavitation bubble will oscillate in the grinding area when the parameter changes.With different parameters,the oscillation amplitude is different.Even for the same parameter changing,the cavitation bubble will show a different vibration amplitude or even only to occur weak oscillation.Among the changes of the honing parameters,the maximum vibration radius of the cavitation bubble can reach 50 times of the initial radius.The model of the collapsed temperature of single cavitation bubble under UVCH grinding zone was established based on energy balance and bubble movement radius changing.The relationship between bubble collapse radius and collapse temperature is calculated.(5)The experiment is conducted for verifying the cavitation bubble collapse thermal effect.The strength of the cavitation effect was tested in two different liquids,respectively,in water and kerosene.The results show that the time and intensity of cavitation are different in every environment.The performances of the cavitation state on various honing oil-stones are also different in the same environment.The thermal damage which was formed by cavitation was tested by aluminum foil in this paper.Different shapes and various size on is formed on foil surface which is relative with the energy of bubble collapse.There are significant effect of the interaction between bubbles on the size of erosion pits.The abrasive will be bonded on foil surface when it affects the aluminum foil coupling with bubble.But the erosion pit has little difference compared with the effect of only bubble which proves that the impact is small formed by abrasive. |
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