Study On The Simulation Of High Efficiency Cutting Hydrogenated Titanium Alloy And Prediction Of Tool Wear

Titanium alloy are widely used in aeronautics and aerospace industry, and civil applications as wellowing to its excellent mechanical properties. However, the poor machinability and the induced rapidtool wear during cutting has limits the further wide application of titanium alloy. Therefore, how toimprove the machinability of titanium alloy has been drawn much attention. In recent year,thermohydrogen treatment technique has provided a potential way to realize the high efficiencycutting of titanium alloy because this special technique could change the microstructure of titaniumalloy. Supported by National Natural Science Foundation of China (50775115), the high-efficiencycutting mechanism and the tool wear behavior are investigated using the finite element simulationmethods. Particularly, the machinability of hydrogenated titanium alloy is studied under thehigh-efficiency cutting circumstance. The influence of the hydrogen content on the titanium alloymachinability and the tool wear are discussed.The major research work is as follows:1. Several key factors in finite element simulation of the cutting process of the hydrogenatedtitanium alloy are investigated.(1) The static and dynamic compression experiments of hydrogenated titanium alloys are carriedout with the material testing machine and split Hopkinson pressure bar (SHPB). The stress-straincurves are obtained at high temperature and high strain rate. The modified Johnson-Cook(J-C)constitutive relations of hydrogenated titanium alloy are derived.(2) The ductile fracture criterion, which is suitable to the cutting process is studied. Fourcommon ductile fracture criterions are compared each other depending on non-linear FEM softwareand compression tests of titanium alloy. The results reveal that the Oyane ctirerion based on cracktheory is suitable to describe the cutting process of hydrogenated titaium alloy. Furthermore, theconstant parameters in Oyane criterion of all hydrogenated titanium alloys are calculated. The resultsare proven valid in the cutting experiments.(3) The friction laws between cutting tool and hydrogenated titanium alloy are analyzed. Theconstant force test platform is designed and applied to simulate the sliding zone of Zorev’s frictionmodel. The sliding friction efficient is measured and compared under different loads, temperature andsliding velocity. The sliding friction laws are therefore obtained.2. The FEM models of the cutting process of the hydrogenated titanium alloy are established. Thesimulated cutting force, cutting temperature and chip morphology are compared with the experimental ones. Furthermore, the FEM models are utilized to simulate the high efficiency cutting process of thehydrogenated titanium alloy.3. The tool wear mechanism is studied during cutting the hydrogenated titanium alloy with opticalmicroscope and scanning electron microscope. At the same time, the relationship between tool lifeand cutting parameters were investigated. The results show that the hydrogenation could improve themachinability of Ti6Al4V alloy.4. The wear rate models concerning different wear mechanism are built according to the wearexperimental results, which include abrasive wear, adhesive wear and diffusion wear. Then the FEMmodel of tool wear simulation is presented. Several problems of tool wear simulation, i.e. predictionof temperature distribution, the updating of tool geometry and the smoothing of wear boundary of toolare presented and discussed. The reasonable prediction of the tool wear is proven feasible in thecutting experiments.5. The tool wear behavior is simulated during cutting hydrogenated titanium based on theestablished finite element model. The effect of cutting parameters on tool wear is investigated. Theexact proportion of different wear mechanism is determined according to the simulation results., Thedominate wear mechanism and the corresponding changing tendency in the cutting process isanalyzed. Moreover, based on the experiment and simulation results, the mechanism of hydrogenationon improving titanium’s machinability is discussed. The reasonable range of the cutting parametersduring high efficiency cutting hydrogenated titanium alloy is provided. Finally, the influence of toolwear on chip morphology, cutting temperature, cutting force and tool stress are investigated.