Analysis And Performance Research On Dynamic Characteristics Of Rotary Composite Boring Bar

Because the traditional metal material boring bar has lower natural frequency and dynamic stiffness,it is easy to chatter in the process of high-speed boring.Flutter affects machining quality and accuracy,which is difficult to meet the requirements of processing technology and reduces tool life.In order to ensure the stability of the cutting process,it is usually adopted to reduce the cutting parameters or improve the static stiffness of the boring bar.However,this will reduce the processing efficiency during the actual process.Moreover,only improving the static stiffness of the boring bar cutter body can not adapt to the complex and changeable processing technology,so a new type of vibration-reducing boring bar is needed to design and develop to improve the dynamic stiffness of the vibration-reducing system and cutting system.It is the best way to improve the dynamic stiffness and basic natural frequency of machine tool structure including boring bar by using composite materials.In this thesis,the dynamic characteristics of composite boring bar are analyzed theoretically and calculated numerically.The structure of composite boring bar is as follows:the tool bar is hollow composite material,the core of damping material is embedded,and the surface of the tool bar is wrapped with metal sleeve.To solve the problem accurately,a large-scale finite element commercial analysis software ANSYS is used to carry out finite element modeling and dynamic simulation of composite boring bar.The object of study includes the dynamic characteristics and harmonic response analysis of static and rotating composite boring bar,undamped and damped composite boring bar.Using the finite element method,studied the effects of the structural design parameters of composite boring bar,including the ply methods of composite material,the types of composite material and damping core material,the thicknesses of adhesive layer and metal sleeve and the length of boring bar,which on natural frequency,whirling frequency,critical speed,Campbell diagram,harmonic response curve,damped natural frequency,modal damping ratio and dynamic stiffness.The results of finite element analysis in this thesis are consistent with those in the literature.The finite element model of composite boring bar is established,and modal analysis and harmonic response analysis are carried out.The effects of different ply methods and structures on natural frequency and amplitude-frequency response curves are analyzed,and the modal analysis of rotary boring bar is carried out to analyze the effects of different ply methods on whirling frequency and critical speed.Damping performance of composite boring bars with five ply methods and different structures is analyzed.The natural frequency,modal damping ratio and amplitude-frequency response curves of composite boring bar are obtained by modal analysis and harmonic response analysis using ANSYS.The whirling frequency,critical speed and dynamic stiffness of the rotary boring bar are calculated.The effects of the natural frequencies,modal damping ratios and dynamic stiffness on the dimensions and materials of different structures of the rotary composite boring bar are discussed.