Analysis Of Dynamic Characteristics Of Rotary Ultrasonic Machine Tool And Research On Grinding Force And Material Removal

Hard and brittle materials have the characteristics of high hardness,high brittleness,and low fracture toughness,making them a typical hard-to-process material.The traditional processing method for processing hard and brittle materials requires multiple procedures.The problems of low processing efficiency,fast tool wear,and severe heat generation make the processing cost of hard and brittle materials high.Rotary ultrasonic machining is a new type of composite technology specifically invented for the processing of hard and brittle materials,which is improved from traditional ultrasonic machining.Rotary ultrasonic machining replaces the free abrasive grains of traditional ultrasonic machining with consolidated abrasive grains.The abrasive grains rotate around the tool axis at high speed while making small ultrasonic vibrations along the tool axis.The material is realized by high-frequency hammering and scoring of the abrasive grains.Processing removal.Rotary ultrasonic machining can directly process hard and brittle materials,which simplifies the process flow,improves the processing efficiency,reduces the grinding force,prolongs the service life of the tool,and shows significant technological advantages in the processing of hard and brittle materials.At present,most of the domestic and foreign rotary ultrasonic machining is achieved by installing an ultrasonic vibration system on the tool holder of the existing machine tool.There are not many special machines for rotary ultrasonic machining,among which Demagee's ultrasonic series is the most famous.In response to this phenomenon,this research group has developed a special machine tool for rotary ultrasonic machining,which aims to further promote the practical application of rotary ultrasonic machining in industrial production.In order to better grasp the actual performance and structural design features of the machine tool,the resonance characteristics are avoided by operating the machine tool below the critical speed.In this paper,the dynamic characteristics of the rotating ultrasonic machine tool involved in the development are analyzed.The dynamic modeling of the joint of the machine tool is the basis for the analysis of dynamic characteristics.In this paper,the dynamic modeling of the linear rolling guide is completed by establishing a spring damping unit between the guide rail and the slider,and the dynamic parameters of the joint between the main box and the base are calculated by using Yoshimura Yonaka's combined area division method to complete the joint.Dynamic modeling has obtained the first nine natural frequencies and modal shapes of the machine tool,which has laid the foundation for subsequent process tests.Hard and brittle materials exhibit different mechanical properties when subjected to different external loads.In this paper,based on the damage and fracture mechanics of hard and brittle materials,the classic JH-2 constitutive model was used to simulate thenano-indentation test of Si C under quasi-static loading,and the load-displacement curves at different pressure depths were obtained.The crack nucleation and propagation of silicon carbide under elastoplastic stress field were studied.Studies have shown that hard and brittle materials will exhibit different mechanical responses under static loading than static loading.In this paper,the dynamic mechanical properties of hard and brittle materials under impact load are studied by performing separate Hopkinson pressure bar test simulation on silicon carbide materials.The damage evolution process and final crushing shape of the silicon carbide specimen under different impact velocities were observed,the strain history diagram of the pressure bar was extracted,and the strain rate of the silicon carbide specimen under different impact velocities was calculated using the three-wave method formula.The dynamic mechanical properties of silicon carbide materials and the reasons for the formation of strain rate effects were laid,which laid the foundation for the subsequent research on the grinding force and material removal under ultrasonic vibration.The impact of abrasive particles in traditional ultrasonic machining is an important factor that distinguishes rotary ultrasonic machining from ordinary grinding.In order to study the grinding force and material removal mechanism of rotary ultrasonic machining,we conducted an abrasive grain impact simulation on the silicon carbide specimen,observed the stress distribution of the specimen after being subjected to abrasive grain impact,and combined the analysis of the research results of the previous chapters The formation and propagation mechanism of micro-cracks is discussed.Under the superposition of sinusoidal high-frequency vibrations,the trajectory of the abrasive particles has changed.Based on the kinematic analysis of a single abrasive particle,the grinding simulation study under ultrasonic vibration was carried out,and the ultrasonic vibration was compared and analyzed.The difference between the grinding force and material removal and ordinary grinding,and the single variable simulation method was used to study the change of grinding force and material removal rate at different vibration frequencies and the reasons were analyzed.The effect and reason of ultrasonic amplitude on grinding force and material removal rate are provided,which provides a reference for the optimization of the process parameters of rotary ultrasonic machining.