Research On Ultrasonic Machining Unit And Cutting Experiments For Hard And Brittle Materials

As a kind of advanced materials with excellent performance, hard and brittle materials have many characteristics, such as high strength, high hardness, high wear resistance, corrosion resistance, thermal insulation, good chemical stability and so on, which brings more difficulties to processing at the same time. Ultrasonic machining (USM) is one of the few methods capable of the implementation of ultra-precision machining of a majority of hard and brittle materials. In this paper, aiming at the USM process of hard and brittle materials, the sandwich piezoelectric transducer and integrated horn are theoretically designed, the USM unit and tools are fabricated, and USM experimental system is established. For zirconia ceramics, the effects of different machining parameters on tool wear and machining quality are studied to summarize the rules.In chapter one the commonly used machining methods of hard and brittle materials at present are introduced as well as the realistic requirement of hard and brittle materials applied in many critical situations in several fields. By analyzing their advantages and disadvantages rotary ultrasonic machining (RUM) using fixed particles is indicated to be applied to almost any type of hard and brittle materials. Then the relevant research situations at home and abroad are introduced from two aspects of USM technology and system. Finally the weak links existing in the current study are summarized, the research meaning is pointed out, and the main research content is proposed.In chapter two the material removal mechanism is introduced as well as the principle of RUM and the trajectory of particles. Finite element analysis is used to research on rotary ultrasonic drilling of ceramics and the effect of feed rate on machining quality is qualitatively obtained.In chapter three the effects of relative properties of the piezoelectric materials and performance parameters of horns on USM unit are introduced. Based on the research on commonly used vibration frequencies and amplitudes of USM of hard and brittle materials the main performance parameters of USM unit are decided and the sandwich piezoelectric transducer and integrated horn are designed. Then the USM unit is fabricated and its composition is described.In chapter four the USM tools are designed and fabricated. USM experimental system is established and each component and its function are introduced. The operation process of the experiment system is described in detail. In addition, the amplitude measurement system of USM tools is established on the basis of the experiment system.In chapter five, the relation among exposed length, resonance current and vibration amplitude of USM tools is studied to summarize the rules. The effects of grit size, vibration amplitude, spindle speed and feed rate on tool wear and machining quality in rotary ultrasonic drilling of zirconia ceramics are studied. Internal causes are analyzed and changing rules are concluded.In chapter six the main research work is summarized, the shortages existing in the research are pointed out, and relevant assumptions and prospects for further study are put forward.