Research On Machinability Of TC4-DT Titanium Alloy And Structural Design Of Bionic Tool

The amount of damage tolerance titanium alloy is increasing with the rapid development of aviation industry, because of its high fracture toughness and excellent fatigue life. TC4-DT damage tolerance titanium alloy has become the key material of aeronautical monolithic component. The fighting performance and service life of new aircraft have been greatly improved. Generally, the processing technology of TC4 titanium alloy has been applied to the process of TC4-DT titanium alloy. But the tool wear and cutting vibration have become more prominent, because TC4-DT titanium alloy has more difficult processability. There are new challenges to achieve the high-speed and high-effciency machining for TC4-DT titanium alloy monolithic component. It is difficult to obtain high processing quality and efficiency when machining titanium alloy structural parts, because that there are large cutting force and vibration caused by the weak rigidity of thin walls and deep cavities. It is an efficient approach to improve the processing quality and efficiency by optimizing the tool structure to make full use of the superb performance of tool materials and coatings.In this paper, the dynamic mechanical properties of TC4-DT titanium alloy at high temperature and high strain rates were studied bsed on the split Hopkinson pressure bar test. The thermal softening and strain rate strengthening effects were researched by analyzing the material stress-strain curves and changes of metallurgical structure. The Johnson-Cook constitutive relationship model under cutting conditions was constructed and applied in the cutting FE simulation. The dynamic mechanical properties of TC4-DT and TC4 titanium alloys were comparatively studied. The different variation of stress and temperature for TC4-DT and TC4 titanium alloys during plastic deformation were revealed.The experiments of milling titanium alloys with the solid cemented carbide milling cutter were carried out. The tool wear morphology was observed by SEM. The element distribution of worn tool surface was detected by EDS. And then the tool wear mechanism was revealed. The relationship among tool wear, cutting force and vibration of milling TC4-DT titanium alloy was investigated to provide a theoretical and technical support for the realization of online check of tool wear state. The cutting force, vibration and surface roughness of milling TC4-DT and TC4 titanium alloys were comparatively studied to assess the milling properties of TC4-DT titanium alloy. The different tool wear criterions for milling TC4-DT and TC4 titanium alloys and the evaluation method of tool tolerant usage based on cutting process parameters were proposed.The design guidelines of tool machining TC4-DT titanium alloy were proposed based on the research of dynamic mechanical properties and milling characteristics. The structure of groove and micro-blade of end mill were designed by observing and imitating the corn leaf’s teeth. The orthogonal cutting models for TC4-DT titanium alloy were developed and parameterized. The structural parameters of bionic tool were optimized according to the results of FE simulation.The bionic tool with designed groove and micro-blade was customized. The experiments of milling TC4-DT titanium alloys were carried out using the bionic tool and comparative tool with the same rake angle, relief angle and helix angle. The excellent cutting performance of the designed tool was verified by comparatively analyzing the cutting force, vibration, temperature, surface residual stress and surface roughness.