Experimental And Finite Element Analysis Of Mechanical Polishing Of Reaction Bonded Silicon Carbibe (SiC)

Silicon carbide(Si C)ceramic is an ideal material for manufacturing the large-aperture lightweight space mirror,however,due to the characteristics of high hardness,high wear resistance,high brittleness,low fracture toughness,chemical stability.Si C has a poor machinability.Chemical mechanical polishing(CMP)which combined the effects of chemical etching and mechanical friction to remove the material is an ideal way to realize ultra-precision machining for material difficult to machine,such as SIC.However,the CMP mechanism,such as material removal mechanisms,form mechanism of the material removal non-uniformity,have not been understood completely.The control of CMP’ process has been depending on the semi-empirical or empirical means in some extend.In this paper to obtain the plan of high material removal rate,high surface quality and high surface planarity of SIC.It is of great significance for the improvement of CMP technology of SIC.From the total integral scattering theory,the roughness of the Si C surface is closely related to its reflectivity,the lower the roughness value,the stronger the reflectivity.In order to obtain high-precision silicon carbide reflector that meet the requirements,the silicon carbide reflectors are usually polished using Continuous Polishing technique.In order to explore the basic rules of Continuous Polishing of the reaction bonded silicon carbide,this paper studied it from the aspects of simulation and experimental.Based on the Preston equation and the rigid body contact model,the factors influencing the removal of the Continuous Polishing and the distribution of the contact pressure between the specimen and the polishing pad.Firstly,a model of relative motion was established to investigate the effects of parameters such as the rotational speed of workpiece and abrasive tool,on the relative velocity and trajectory distribution of the workpiece.On the basis of the trajectory distribution,the influence factors of wear of workpiece and abrasive tool and the conditions to implement the uniform wear of them in CMP were analyzed.A CMP simulation model was established by using ABAQU software in the case of direct contact between workpiece and polishing pad,the effects of the polishing pressure,the thickness,elastic modulus and poison’s ratio of polishing paid and the friction coefficient of workpiece and polishing pad on the contact pressure distribution.The experiments of chemical mechanical polishing of Si C were conducted on the basis of the above technique analysis.The surface planarity was described as the arithmetic average deviation of surface profile after polishing.In the CMP process,the effect of polishing pressure.Relative velocity,slurry concentration,polishing pad,and retaining ring on the material removal rate,surface roughness,surface morphology and surface planarity in chemical mechanical polishing of silicon carbide ceramic were studied by using single factor experiment method.