| With the increasingly demanding of gear transmission accuracy,load,life-span and noise in automobiles,wind turbines,robots,etc.,it has become more urgent to apply internal power honing to finish high performance hardened gears.However,the research on the microscopic morphology of the randomly distributed irregular abrasive grains on the tooth surface of the honing wheel and the interaction law of the workpiece is relatively insignificant,hindering the wide application of internal power honing technology in the finishing and polishing stages of hardened gears.This thesis focuses on the CBN abrasive micro edge honing of high-quality hard tooth surface gears,as outlined below:1.Based on the principle of internal power honing,the equations of the tooth surface of the workpiece,the equations of the honing transient traces and the equations of the honing wheel tooth surface are solved.Taking the honing wheel and workpiece as the research object,by using the kinetic principle,the equations of honing speed,honing force,honing power and specific grinding energy are given to establish the theoretical basis of internal power honing.2.Simplify the CBN abrasive grain as a regular quadrangular conical shape,define the cutting geometry angle of the abrasive grain,and derive the analytical formula of the average grinding edge interval,wear amount,effective cutting depth,active grinding edge number,effective contact arc length and average honing cross-sectional area.A threedimensional cutting model between abrasive grain and workpiece was established to investigate the mechanism of chip generation,and revealed the different shapes,sizes and thicknesses of chips generated by different microtopography of honing wheels and honing process parameters under the action of shear and frictional work of workpiece materials.The radar method was applied to measure the shape and size of the grinding chips,and the theoretical formula for the thickness of the grinding chips was solved by using the method of calculating the average cross-sectional area of the undeformed grinding chip thickness.The results show that the microscopic shape of the honing wheel and the parameters of the honing process are the main factors affecting the removal of workpiece material by the CBN honing wheel during the low-velocity cutting process of multiabrasive micro-edges,which has an important impact on the honing quality.3.The microtopography of a honing wheel surface composed of active abrasive grains is the key factor affecting the honing characteristics,and control of it is a sufficient condition to realize high-efficiency precision honing.Based on the magnetron sputtering method and phase field method,a theoretical model of CBN coating formation on a honing wheel surface was established.The physical vapor deposition(PVD)discrete phase field equation was solved by the finite difference method.A MATLAB program was compiled to simulate the formation process and micromorphology of the CBN coating on the honing wheel surface.A Taguchi method was designed to study the relationships of the sputtering time,substrate temperature,gas flow rate,and reaction space with the number of active abrasives and the length,width,height,and size of the abrasives.The reliability of the simulation results was verified by experiments.The results show that plasma energy(charge energy ions)drives the migration,rearrangement,coalescence,and nucleation of boron and nitrogen atoms in the matrix,which is also the driving force for the growth,coarsening,and film formation of CBN grain nuclei.The higher the plasma energy,the faster the growth and coarsening rate of columnar grains and the better the film quality.The sputtering time,substrate temperature,gas flow rate,reaction space and the number and size of CBN grains are of high significance level and should be mainly controlled.The process parameters are related to the active abrasive grain shape and spacing with low significance level,and were controlled as secondary factors.Therefore,reasonable selection or optimization of process parameters can quantitatively control the number,size and distribution state of abrasive grains,improve the microscopic morphology of CBN coating on the honing wheel tooth surface,and thus help to improve the processing performance of honing wheels.The simulation topography is in high agreement with the SEM results,indicating that this study can accurately and effectively simulate the tooth surface abrasive topography under different process conditions,which provides guidance for the design of CBN abrasive microtopography on the tooth surface of grinding wheels and the manufacture of honing wheels,and hence fundamentally improves the material removal rate,machining accuracy and surface finish quality of hardened gears.4.By obtaining the information of the random distribution state of the position,orientation and number of CBN abrasive grains on the tooth surface of honing wheels,the internal power honing process can be equivalently transformed into a micro-edge cutting model for the random distributed active abrasive grains in the cells of the meshing area.The results show that although the active abrasive grains are distributed at different locations,they all experience three types of material removal:slip rubbing,ploughing and cutting,making honing have the integrated processing characteristics of grinding,lapping and polishing.The processing characteristics of the first contacted active abrasive grains on the workpiece material show high honing force,high material removal efficiency and poor surface roughness of the workpiece,while the latter contacted abrasive grains are just the opposite.Different orientation angle affects the chip shape and chip removal direction.When the orientation angle was 75°,the chips were fine and the chip removal performance was good,but the honing force constantly oscillated between 0.02N-0.045N.With a given contact area,the number of active abrasive grains increased from 17 to 21,the average interval distance of abrasive grains decreased,less material remains after cutting,and the material removal rate increased from 68.58%to 84.68%.5.By analyzing the factors affecting the quality of internal power honing,a comprehensive evaluation and optimization model of multi-abrasive micro-edge honing process was established based on Trapezium Fuzzy Analytic Hierarchy Process(TraFAHP)and Set Pair Analysis(SPA)method.By using the key factor analysis and sensitivity analysis,the honing process parameters and grain size,grain falling off and grain breakage are quantitatively determined as the key factors influencing honing performance.To verify the reliability of the model,honing experiments were conducted to investigate the effect of grain size on the quality of honed teeth.The results showed that when the grain size in the range of 100#<300#<540#,the average value of total deviation of spiral line decreased sequentially;the distribution of tooth distance deviation gradually approached the zero line,and the correction ability of the variation of common normal length was enhanced;the average value of total deviation of tooth profile decreased;the error reversion coefficient was reduced,and the precision of honing processing improved.As the grain size increased,the average grain spacing decreased,leading to a reduction in the maximum valley height Hv,which in turn reduced the surface roughness value Ra and improved surface quality.With the reduction of grain size number,the cutting performance turned better,the honing processing efficiency increased significantly,and hence a small grain size is suitable for rough honing.The comprehensive evaluation results show that 300#CBN abrasive honing is the best and 540#CBN abrasive honing is the worst. |
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