Study On Surface Quality Of Bearing Raceway In Ultrasonic Vibration Precision Grinding With Ceramic Bonded CBN Grinding Wheel

As the most widely used general mechanical parts in rotating machinery,rolling bearing’s performance directly restricts the quality of high-precise equipment,and the manufacture of high-performance bearings has become a bottleneck to restrict the rapid development of manufacturing industry in our country.High performance bearings require high precision,high surface quality,high load capacity,long life and high reliability.As the working surface of bearings,the surface quality of bearing raceway obviously affects the performance and service life of bearings.Common grinding processing tends to produce poor surface quality,high grinding force and high temperature,therefore,it is an important task to develop new technology and new technology to improve the level of grinding technology in bearing industry.Ultrasonic vibration assisted machining is a composite machining method which superimposed ultrasonic into the process of workpiece material removal.The transducer(piezoelectric ceramic)is used to convert electric energy into high frequency mechanical vibration energy,and improve the machining quality of workpiece surface by changing the contact state between abrasive particles and workpiece.In this paper,based on the national key research and development project of “ultra-precision machining technology and equipment for high surface quality raceway”,ultrasonic is applied in the manufacturing process of bearing raceway,considering the dressing mechanism of grinding wheel,the surface roughness and the heat and force based on the thickness distribution of undeformed chips in ultrasonic grinding process are studied.The main research contents are as follows:(1)Aiming at the difficulty of resonance design of large-load ultrasonic grinding system,this paper designed the large-load grinding wheel as spoke wheel,and equivalented it into a composite model of hub as cylindrical rod,spoke plate and wheel rim as mediμm and thick plate.The frequency equation of the system was deduced by the continuous boundary conditions of each contact surface,the ultrasonic vibration grinding system design was completed,the experimental device was also manufactured,and the acoustic vibration characteristics of the device were analyzed and verified.The experimental results showed that utilizing the spoke-type compound model to obtain the system frequency equation was effective for solving the design problem of the large-load ultrasonic vibration grinding system.(2)The kinematics method was utilized to analyze the relative motion relation between the roller and the grinding wheel surface,the roller dressing mechanism on the grinding wheel was expounded,the dressing process was simulated by computer to visualize the dressing track of the roller,and the influence law of different dressing parameters on the dressing track was analyzed,the surface evaluation parameters of the grinding wheel topography under different dressing parameters were predicted,the dressing effect of the roller was evaluated quantitatively,and the mapping relationship between the dressing parameters and the surface topography of the grinding wheel was established.The morphological characteristics and evolution process of grains under different dressing parameters were compared and observed through experiments to further understand the dressing process of grinding wheels.(3)The microscopic mechanism of interaction between abrasive particles and workpiece materials during ultrasonic grinding was deeply analyzed.The dressed grinding wheel was introduced to simulate the random cutting process.The surface morphology generation model considering grinding kinematics and abrasive randomness was established to calculate the undeformed chip thickness(UCT)by the symbolic difference method.The distribution characteristics,including the mean,maximum and variance of cutting thickness and the effective abrasive number,were extracted.The influences of dressing parameters,ultrasonic parameters and machining parameters on UCT distribution were comprehensive analyzed,and the linear relationship between the mean value of UCT distribution and surface roughness was obtained.Finally,the influence of grinding parameters on surface roughness was verified by experiments.The influence law of grinding parameters on surface roughness is consistent with the change of UCT distribution.The prediction values are in good agreement with the experimental results.(4)According to the interaction mechanism model between abrasive particles and workpiece material in the ultrasonic vibration grinding contact zone,the interference depth of each abrasive particle and workpiece was obtained,and the grinding stage and grinding force of each stage was determined,and the ultrasonic vibration grinding force model was established.On this basis,the temperature field model of ultrasonic vibration grinding process was calculated.The grinding force and temperature model are verified by single factor experiment.The predicted values of ultrasonic grinding force and temperature are consistent with the experimental values by single factor test.The sensitive parameters affecting grinding temperature were determined as grinding depth and dressing transverse feed rate by orthogonal experiment,and the corresponding relationship between grinding temperature and grinding burn metamorphic layer was established,which provided the basis for preventing grinding burn.Finally,the relevant theories were applied to the process planning of ultrasonic grinding of bearing raceway,and the process parameters of bearing raceway grinding for batch production were obtained to meet the requirements of the subject.Number of Figures:112,Number of Tables: 31,Number of References: 187.