| Engineering ceramic materials represented by silicon carbide(Si C)ceramics has excellent properties such as high temperature resistance,wear resistance,and high hardness,which is widely used in fields such as aerospace,medical equipment,automotive manufacturing,and intelligent equipment.However,due to the hard brittleness of Si C ceramics,traditional machining methods have problems such as high grinding force,severe surface damage,short tool life,and low machining efficiency.Ultrasonic assisted machining can effectively improve these problems.Among them,rotary ultrasonic grinding(RUG)combines ultrasonic vibration with conventional grinding(CG),which has the advantages of high surface quality,high efficiency,and high strength,and has become an effective machining technology for grinding ceramic materials.Although there is currently a mature resonant tool system for RUG,there is relatively little research on the resonant tool system with large-sized straight grinding wheel due to the difficulty of resonance in large-sized grinding wheels.The existing modeling process of grinding wheel machining trajectory is complex and difficult to reproduce,which limits the promotion and application of simulation technology in the investigations of RUG.The research on the impact of RUG technology parameters such as grinding wheel material,machining parameters,and resonance parameters on the surface quality of machining is not comprehensive enough.Therefore,this article has proposed the design method and amplitude control method of the straight grinding wheel amplitude transformer,established a simulation model of the machining trajectory of the straight grinding wheel,conducted machining experiments using the developed straight grinding wheel resonance tool system,and investigated the influence of RUG technology parameters on surface quality.The main content includes:(1)The theoretical analysis model of the amplitude transformer with the circular plate straight grinding wheel has been established.By analyzing the vibration mode of the tool system,it was determined that the large-sized straight grinding wheel amplitude transformer adopts the node-circle transverse flexural vibration mode.The theoretical model of the annular plate straight grinding wheel amplitude transformer was established,and an example design was carried out based on this theoretical model.The correctness of the theoretical model was verified through finite element modal simulation analysis.The establishment of the theoretical model of the amplitude transformer with straight grinding wheel provides a theoretical basis for the development of the large-diameter resonant tool system with straight grinding wheels.(2)A method of setting up the ring groove on the surface of the straight grinding wheel to achieve amplitude regulation was proposed.Based on the geometric model of the design example,the influence of ring groove parameters on amplitude was analyzed using finite element harmonic simulation and orthogonal design.The investigation results indicate that the position of the ring groove has little impact on the amplitude,the width of the ring groove is positively correlated with the amplitude,and the depth of the ring groove is negatively correlated with the amplitude.By changing the parameters of the ring groove,the amplitude control of the straight grinding wheel amplitude transformer can be achieved,providing a reference for the design of the large-diameter straight grinding wheel resonant tool system.(3)A trajectory model for RUG with straight grinding wheel was established,and the influence of RUG technology parameters on surface roughness was investigated.A simulation model for the abrasive layer of the straight grinding wheel was established.An improved kinematic equation of abrasive grains was used to establish a simulation model for the trajectory of abrasive grains.An algorithm for generating machining surface morphology was proposed and applied to the grain motion trajectory model.A straight grinding wheel machining trajectory model was obtained and described using the surface roughness parameter Ra.Based on the trajectory model of straight grinding wheel machining,numerical simulation technology and orthogonal design were used to analyze the influence of technology parameters such as grinding speed,feed speed,and amplitude on Ra.A matching scheme for RUG technology parameters was obtained.Provided a recurrent machining trajectory simulation modeling process,which has application reference for optimizing the combination of RUG technology parameters.(4)A resonant tool system for RUG with straight grinding wheel was developed and the resonant characteristics of the resonant tool system was tested.Based on the design method of the resonant tool system and the orthogonal experimental scheme of technology parameters,six sets of RUG straight grinding wheel resonant tool systems were developed with different frequencies of 20 k Hz,28 k Hz,and 35 k Hz,as well as different bonds and abrasives of resinoid bonded,electroplated diamond,brazed diamond,and electroplated CBN.The resonant characteristics of the developed resonant tool system was tested using impedance experiments,vibration mode The resonant characteristics of the developed resonant tool system was tested using impedance experiment,vibration mode experiment,and amplitude measurement experiment.The results showed that the developed resonant tool system can meet the machining requirements and provide equipment support for machining experiments.(5)The machining characteristics of resonant tool systems for straight grinding wheels with different abrasive bonds was evaluated.Full factorial experiments on straight grinding wheels of different materials were carried out on reaction-sintered Si C ceramics workpieces using resinoid bonded diamond,electroplated diamond,brazed diamond,and electroplated CBN straight grinding wheel resonant tool systems,with rotational speed and grinding mode as variables.The experimental results showed that the electroplated diamond straight grinding wheel has lower grinding force,and the machining surface quality of resinoid bonded diamond and electroplated CBN straight grinding wheel was better.Compared to CG,RUG produces lower grinding force and can better surface quality.The research of this experiment provides experimental reference for the selection of straight grinding wheels in RUG.(6)The influence of RUG technology parameters on the surface quality of the machined surface was investigated.An orthogonal experimental scheme was designed for RUG of reaction-sintered Si C ceramics workpieces,including spindle speed,feed speed,grinding depth,amplitude,and frequency.Considering the practical application requirements of the workpieces,the influence of technology parameters on the roughness Ra,Rq,Rsk,and surface roughness Sa,Sdr,Ssk,Smr1,and Smr2 was analyzed.Comprehensive analysis shows that when the resonant frequency is 20 k Hz and the spindle speed is 1000-2000r/min,better surface quality can be obtained.The investigation of the influence of technology parameters on the surface quality of machining provides an experimental basis for the matching research of RUG technology parameters.This article established the theoretical analysis model of the straight grinding wheel amplitude transformer and developed the resonant tool system for RUG with large-diameter straight grinding wheels,provides an efficient and high-quality method for the machining of hard and brittle materials.Simulation and machining experiments reveal the influence of RUG technology parameters on surface quality,which provides an experimental basis for the selection of straight grinding wheels and the matching of technology parameters.This article is of great significance for the development,application,and optimization of the resonant tool system for RUG. |
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