| In China,the strategy of large aircraft manufacturing had been put into the next 15-year development projects.In addition,the strategic support and guarantee for aerospace equipment manufacturing had been proposed in "Made in China 2025".Clearly,the aviation industry is increasingly prominent.As for aero-engine,its property is mainly determined by the manufacturing level of blade.Blades belong to the typical thin-walled parts and the processing process prone to chatter due to shape-shifting and unique shape(with free surface).What’s more,the processing chatter easily leads to the poor surface quality and the low production efficiency.Thus,it is important to analyze the processing principle of blades,to predict the stable region of blade and to study the processed surface quality of blade.This thesis was carried out from the general plane to specific surface and from the simple thin-walled parts to complex blades.Based on the design and determination of blade profile,through the cutting force model,2-d and 3-dimensional processing dynamics model,stability and surface profile model of milling machine,this paper analyzed the cutting force and the chatter stability in the manufacturing of blades,as well as made a research on the processed surface quality of blade by related experiments.The content is summarized as following:(1)The reasonable profile is constructed by analyzing the blade profile parameters of general turbine blades and applying the quintic polynomial.In addition,the CAM software and computer optimization and simulation technology are applied here,then the numerical control machining program is compiled and optimized.And this program is used to guiding the actual processing of titanium-alloyed blade by the high-fidelity machining simulation.(2)With analogizing the principle of orthogonal lathe milling,the parameters of the blade compound milling machining are analyzed,and the model for three-axis machining force of ball-end milling cutter is constructed.Besides,the milling forces is predicted by the cutting coefficient of the linear force model obtained in experiments.Then the influence of different parameters on milling force is analysed.Apart from above mentioned,the force model is extended to multi-axle turn-milling by transformation matrix introduced.(3)Based on regenerative effect,a 2-dimnetion milling dynamic model for general workpiece is constructed considering workpiece flexibility and is extended to the solution of 3-dimensional dynamic turn-milling force.Besides,according to the modal parameters observed in experiments,based on the relative transfer function of system and the time domain simulation verification,the stable machining area for complex thin-walled parts(blades)is predicted by analyzing the processing stability of thin-walled parts through frequency domain method and time domain method.(4)From the perspective of macroscopic texture and microscopic appearance,the difference between the chatter surfaces and stable surfaces of ordinary thin-walled parts is analyzed based on the quantitative comparison and qualitative observation for experimental data.In addition,the surface residual height model of orthogonal lathe milling is constructed and is specialized to the surface appearance of blade milling.Then some suggestions on choosing parameters are proposed for better surface quality obtained based on the simulation analysis for the effect of different parameters on the surface quality of turn-milling blade. |
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