Study On Material Removal Mechanism Of Zirconia Ceramics Grinding Based On Modeling Of Grinding Wheel Topography

Engineering ceramics are widely used in many important fields,such as aeronautics and Astronautics,national defense and military industry and modern medicine for its excellent properties,such as high strength,high hardness,wear resistance,high temperature resistance and chemical corrosion resistance.At present,the most mature and practical method in engineering ceramics processing is the grinding wheel.Many factors such as the number of abrasive particles on the surface of the grinding wheel,the complex shape of the abrasive cutting edge,the randomness of the abrasive size,the randomness of the position and the grinding process parameters,make it difficult to study the removal mechanism of the grinding material.Grinding process is a dynamic process.Its grinding mechanism is mainly based on theory and experiment,and there are difficulties in detecting related physical quantities and phenomena.Therefore,in order to study the material removal mechanism of precision grinding for engineering ceramics,we need to do finite element simulation for grinding process.In this paper,zirconia ceramic precision grinding is taken as the research object,and a new index for evaluating the surface topography of grinding wheel is put forward according to the characteristics of the surface topography of the grinding wheel.On the basis of the measurement and evaluation of the surface morphology of the grinding wheel and the definition of the shape of the abrasive grain,the surface morphology of the grinding wheel is modeled,and the new evaluation index of the grinding wheel morphology is introduced to the modeling of the grinding wheel morphology,so that the model is more close to the reality.The finite element model of grinding is established,and the finite element simulation analysis of zirconia ceramic grinding is carried out,and the material removal mechanism of zirconia ceramic grinding is analyzed.The precision grinding experiment of zirconia ceramics is carried out,and the experimental results are compared with the simulation results to verify the correctness of the simulation.The material removal mechanism of zirconia ceramics is further revealed,and the basis for reasonable selection of grinding parameters and improving the quality of zirconia ceramics is provided.The specific research work are as follows:1)Two new indexes,the degree of grain protrusion area ?d and the degree of grain protrusion area dispersion ?s were proposed to evaluate the surface topography of the grinding wheel.The influence of the different dressing conditions on the surface orphology of the grinding wheel was evaluated by ?d and ?s,thus guiding the dressing of the grinding wheel.The diamond grinding wheels with different ?d and ?s obtained by dressing were used for grinding experiments,and the grinding force during grinding and the grinding surface roughness after grinding were analyzed,and the surface topography characteristic parameters ?d and ?s of diamond wheel were selected to optimize the finishing quality and the highest grinding wheel performance.2)Through the detection of the shape of grain,9 kinds of model of abrasive grain shape,and the proportion of it are defined.By measuring the surface of the grinding wheel,the parameters of the grinding wheel surface like the degree of grain protrusion area ?d and the degree of grain protrusion area dispersion ?s are obtained.The use of random numbers defines the size of the abrasive grain,the coordinates and angle of the abrasive grain position,and defines the height of the surface of the grain bonding on the surface of the grinding wheel.By adjusting the plane height of the binder and the distributing parameter ?2 of the height of protrution of the abrasive grain,the ?d and ?s of the grinding wheel model match the actual situation.Finally,the grain density,the average spacing and the height of protrution of the diamond grinding wheel surface are verified.3)On the basis of the modeling of the surface of the grinding wheel,the finite element model of the grinding wheel and the workpiece is established.The simulation scheme is designed with Box-Behnken,and the grinding simulation is carried out by the finite element model.The grinding force,roughness,damage depth and crushing rate are analyzed and analyzed by the variance analysis.The results show that the grinding depth has the most influence on the crushing rate.Based on Bifano's definition of plastic removal,a single-factor simulation process parameter scheme was designed for grinding depth.Through simulation,when the grinding wheel rotation speed was 31.42 m/s,the workpiece speed was 20 mm/s,and the grinding depth was 2.69 ?m,the crushing rate was 9.45.%(less than 10%)is the critical point for brittle-plastic removal.4)The grinding experiment of zirconia ceramics was carried out,and the grinding force,roughness,damage depth and breaking rate were detected and compared with the simulation results to verify the accuracy of the simulation.The critical load model A of transverse crack is used as a critical load condition model for removing brittle-plastic of zirconia ceramics.The critical grinding depth obtained in the simulation is tested,and the normal grinding force per unit area method is obtained,and the parameter C is 0.56,and the validity of the critical load condition model is analyzed through experiments.