The Simulation And Experimental Research On Ultra-Precision Fly Cutting Of Zirconia Ceramics

As an advanced engineering material,zirconia ceramic has been widely used in aerospace,biomedical,and information and communication fields due to its excellent material properties,such as high hardness,high temperature resistance,wear resistance,and ablation resistance.However,zirconia ceramics is a typical hard-brittle material,brittle fracture in the machined surface and rapid tool wear often occur during cutting process,which seriously restricts its large-scale promotion and use.Good surface integrity is needed in the cutting process of zirconia ceramic.As a kind of ultra-precision machining technology,diamond fly-cutting shows great feasibility and advantages in cutting this material due to its high machining accuracy and efficiency.Based on the theory of brittle-ductile transition of brittle materials,the removal mechanism of zirconia ceramics has been analyzed by SPH cutting simulation,and an ultra-precision flying-cutting sub-platform has been built.The diamond fly-cutting zirconia ceramic test has been carried out on the built processing platform in order to explore the machinability of zirconia ceramic.The ultra-precision fly-cutting processing sub-platform has been built on the existed three axis ultra-precision milling machine.After the structural design of the fly-cutting system,the dynamic characteristics are analyzed by finite element simulation.the simulation results show that the natural frequency of the system is much higher than its rotational frequency,so the resonance can be effectively a voided.In addition,the deformation of the fly-cutting disk is small during high speed rotation,which has little impact on the machining process.A method and equipment for dynamic balance debugging of flying-cutting system has been designed in order to ensure that the balance accuracy grade was within the accuracy requirement of the air spindle.The micro-mechanical properties of zirconia ceramics were measured by nanoindentation and Vickers indentation experiments,and the critical cutting thickness of brittle-ductile transition was estimated using the Bifano empirical formula.An SPH cutting simulation model of zirconia ceramics was established in LS-DYNA based on the JH2 constitutive model.The material removal mechanism,chip morphology,crack generation and propagation pattern in the brittle/plastic cutting process were investigated through simulation analysis.The influences of different process parameters and tool parameters on cutting force,stress,strain,and brittle-ductile transition were analyzed.The critical cutting thickness of brittle-ductile transition was measured by fly-cutting experiment to verify the simulation model.The precise fly-cutting tests of zirconia ceramic have been carried out by radial and axial fly-cutting methods on the built ultra-precision fly-cutting processing sub-platform.The surface topography,cutting force,and tool wear during the cutting process were analyzed in order to explore the machinability of zirconia ceramic.Finally,the ductile domain precision cutting of zirconia ceramic has been realized and a high quality machining surface has been obtained by controlling the maximum undeformed chip thickness in the fly-cutting region.