Study On Grinding Mechanism Of Zirconia Ceramics By Longitudinal-Torsion Ultrasonic Vibration Milling

Due to the excellent mechanical and physical properties and stable chemical properties of hard and brittle materials,they are increasingly used in military,precision manufacturing,medical beauty and other related fields,but ceramic ceramic hard and brittle materials are prone to materials during traditional grinding.It shows the collapse and collapse,and the change of the temperature gradient in the grinding area causes the thermal stress to change greatly,resulting in micro-cracks or even macro-cracks,which causes the surface quality to be degraded.This article has read a lot of domestic and foreign ultrasonic vibration processing materials.On the basis of the papers,and selecting zirconia ceramics as the research object,the basic research on the removal mechanism of ceramic materials for longitudinal torsional composite ultrasonic vibration milling is carried out,and the interaction between diamond abrasive grains and ceramic materials is analyzed,combined with kinematics.The theory is to deduct and simulate the abrasive grain trajectory of longitudinal torsional ultrasonic vibration processing,and to derive the grinding force model of the abrasive grain on the side of the milling head in the feeding direction according to the movement track of the abrasive grain,and to measure the grinding force and the scratch by the grinding force.The experiment explores the mechanism of longitudinal torsional composite ultrasonic vibration processing.The main research work is as follows:(1)Firstly,according to the various descriptions of the longitudinal torsional ultrasonic vibration system of the external ultrasonic power supply,combined with the vibration mode of the longitudinal torsional ultrasound,the interaction between the abrasive particles and the ceramic workpiece is analyzed based on the kinematics theory basis,and then the equation of the motion of the abrasive particles is derived.The simulation is carried out.Through the establishment of the trajectory model,the arc length of the abrasive particles during the machining process and the theoretical removal volume of the material prove that the longitudinal torsional ultrasonic machining can increase the effective motion distance on the basis of changing the traj ectory of the abrasive particles.(2)Based on the analysis of the trajectory equation of longitudinal torsional composite ultrasonic vibration machining,the effective number of abrasive grains in the machining process is analyzed.Combined with the theory of brittle fracture mechanics,the grinding force model of the upper surface of the milling tool in the feed direction is derived and simulated.The grinding force test platform was built,and the three-way force of longitudinal torsional composite vibration machining was measured by single factor milling zirconia experiment,and the correctness was verified by comparison with the simulation value.(3)Based on the analysis of the abrasive trajectory of longitudinal torsional composite ultrasonic vibration machining and the derivation of the grinding force model,based on the propagation principle of stress wave and brittle fracture mechanics,a differential equation of stress wave based on single abrasive grain is established,combined with generalized Hooke’s law establishes the mathematical model of stress wave,and then solves the mathematical model of stress wave by numerical simulation method of finite difference.The results show that compressive stress and tensile stress appear in the material due to the inertial effect of the internal particle of the material.The initiation and propagation of cracks were simulated by Ansys finite element simulation software,and the stress field of zirconia ceramics was simulated and analyzed with finite difference numerical simulation results.(4)Combined with the grinding force prediction model,the longitudinal torsional composite ultrasonic vibration milling process,the longitudinal ultrasonic machining and the ordinary milling machining comparison single factor force test,analyze and contrast the influence law of the three processing forms,and verify the grinding Through the above three forms of scratch test,qualitatively explore the mechanism of material removal in longitudinal torsional composite ultrasonic vibration processing,and compare the critical depth of material brittle plastic transformation under three kinds of scratches.The results show that:The block-like cracking of ultrasonic scratches is significantly slower than that of ordinary scribes,while the longitudinal twist marks are smoother,and the critical depth of scratches increases as the scratch speed increases,and is compared by tool wear test.Wear of single diamond abrasive grains in three forms.