Study On Edge Chipping At The Small Hole Exit In Rotary Ultrasonic Milling-grinding Of Microcrystalline Mica Ceramics

With the development of advanced science and technology,traditional materials and processes have been unable to achieve the performance of high-end fields such as aerospace,high-tech and biomedical.Microcrystalline mica ceramics have potential advantages in these fields by virtue of their physical,chemical and biological characteristics.However,the hard and brittle nature of microcrystalline mica ceramics makes it difficult to process,and it is easy to cause cracks and edge chipping,which results in poor surface quality of the workpiece after processing and cannot meet the requirements of practical application.Ultrasound vibration millinggrinding hole processing is a combination of traditional milling-grinding and ultrasonic vibration,in order to achieve high-efficiency and high-quality processing of microcrystalline mica ceramics small hole.Ultrasonic vibration assisted machining changes the material removal mechanism and has a good effect on brittle material processing,which can reduce cutting force and subsurface damage.Millinggrinding can change the trajectory of abrasive particles,which is beneficial to the discharge of chips and reduce the cutting temperature.At present,the research on the removal mechanism of microcrystalline mica ceramics is mainly through quasi-static nanoindentation experiments or scratch experiments.The research on the mechanism of material removal during ultrasonic vibration assisted scratch is still in the exploration stage.Moreover,the research on ultrasonic vibration-assisted machining of hard and brittle materials mainly focuses on surface morphology and roughness.There is still no complete theoretical basis for the study of microcrystalline mica ceramics small hole processing exit chipping,so ultrasonic vibration milling-grinding of small holes is of great significance for the study.In this paper,the trajectories of abrasive grains in traditional milling-grinding and ultrasonic vibration milling-grinding were compared.The removal mechanism of ceramic materials during ultrasonic vibration assisted machining was described from the kinematics of abrasive particles.The removal process and internal stress distribution of the materials were analyzed by scratch simulation.The morphology of the surface of the trench and the critical depth of the brittle-plastic transition were analyzed by microcrystalline mica ceramic scratch experiments.The effects of ultrasonic vibration on the plastic domain of the brittle material were studied by comparing the morphology of the ultrasonic.The results of simulation analysis and scratch experiments provided the basis for subsequent milling-grinding processing research.The ultrasonic vibration milling-grinding process was simulated by finite element method,and the formation process of exit chipping was studied.Based on the Hertz contact formula of maximum contact force,the first and second chipping formed after ultrasonic vibration milling-grinding were theoretically modeled.Finally,the ultrasonic vibration milling-grinding experiment was designed and the exit chipping evaluation index was established.The influence of processing parameters on the exit chipping index was studied.The single factor experiment was used to improve the prediction model and the orthogonal experiment was used to verify the prediction model.It provided a theoretical basis for the optimization of processing parameters.And based on the optimized parameters,an exploratory study on the efficient machining of deep-small hole ultrasonic vibration milling-grinding was carried out.