Study On Machining Stability And Process Optimization Of Titanium Alloy Thin-walled Parts

With the development of aerospace science and technology,the titanium alloy thin-walled part is used increasingly.Due to sophisticated shape and poor stiffness,the machining accuracy is easily affected by deformation which generates in the process of clamping and cutting.Thus,the prediction and control of the instability in the milling process of thin-walled parts has become the issues of aerospace industry need to be resolved.In this paper,the titanium alloy thin-walled part with ear surface is applied to do research on the prediction of stability,the impact of fixture layout on the stability and the maching problem between the cutting radial depth and the stiffness of the thin-walled part during side-wall milling process.The main research is as follow:1) Based on the milling system,a instantaneous cutting force model and a dynamic cutting force model for thin –walled parts is established is established in the paper.Besides,in order to verify the established cutting force model,a series of milling experiments are conducted.2) The finite element method is applied to identify the modal paramenters of the spindle-cutter system, and by conducting the modal experiment, the finite element model is verified.A method is proposed to predict the stability domain of milling system and analyze the impact of cutting force coefficients,natural frequency and damping ratio,and radial cutting depth on the stability of milling system.3) Taking the ear-shaped thin-walled structure as the research object,a method for fixture layout design is put forward,using the method of Harmonic response analysis which aimed at suppressing machining vibration of thin-walled part during the milling process. By conducting a milling experiment of ear-shaped thin-walled structure,the method for fixture layout design is verified.4) Based on the typical thin-walled structure,a layer cutting model is built in order to study the maching problem between radial cutting depth and stiffness of the structure.Using finite element method and genetic algorithms,opmization of radial cutting depth of each layer is conducted.The opmized distribution of radial cutting depth is able to reduce the deformation of the thin-walled structure.5) A software for cutting simulation of thin-walled part with ear surface is established based on Visual C++,which achives functions of the input of dimensions and cutting parameters,clamping plan selection and viewing simulation results.The software can reduce the load of researchers with simple and easy operation interface.