Parametric Modeling Of Milling Titanium Alloy And Prediction Of Tool Wear State

Titanium alloy is widely used in aviation and aerospace fields due to excellent comprehensive performance, known as a strategic metal material making the human to the space age. However, titanium alloy is a typical difficult-to-machine material for poor thermal conductivity, low elastic modulus and high chemical activation. High cutting temperature generated during titanium alloy machining usually leads to fast tool wear and poor surface quality. On the other hand, most materials need to be removed from roughcast due to the design characteristics of components used in the aircraft industry, resulting in increasing the processing difficulty. Cemented carbide is widely used in machining titanium alloy materials because of excellent performance. However, cemented carbide tool wear is a prominent problem. Serious tool wear not only has great influence on machining efficiency and quality, but also on the processing cost. There is a lack of effective method of tool life prediction for titanium alloy processing. Therefore, the study of tool wear model, prediction of tool wear extent, and monitoring tool wear state have become worthy of attention for titanium alloy processing.This paper discussed the tool wear characteristics and regularity of cemented carbide under the action of coupled thermo-mechanical field for titanium alloy Ti6AI4V processing. The cutting force in milling of Ti6A14V was firstly studied from two aspects of theory and experiment. There is the close correlation between the cutting force and cutting temperature in cutting process. Therefore, the cutting temperature variation in milling Ti6A14V was discussed and cutting temperature model in milling was established based on the classic heat transfer theory. The experimental study to measure cutting temperature in milling Ti6A14V utilizing semi-artificial thermocouple was presented. Then the thermo-mechanical coupling effect for carbide tool wear was discussed and the tool wear model was proposed considering the temperature effect. Finally, the prediction of tool wear state was obtained from the secondary development of AdvantEdge simulation software.Cutting force is an important parameter in cutting process, which has the important influence on the cutting power, cutting heat, tool wear and machining distortion. Meanwhile, the tool wear could also lead to the variation of cutting force. Machining process is the process of motivation and interaction between cutting force and tool wear. The cutting force allowing for tool wear effect in milling of Ti6A14V was studied from two aspects of theory and experiment. First of all, orthogonal and oblique cutting force model was established based on the classical shear angle theory and Armarego oblique cutting theory respectively. Then cutting force model allowing for tool wear effect was obtained. Finally, the modeling of three-dimensional cutting force in end milling considering tool wear was discussed by means of discretization thought. In addition, the experimental work of end milling Ti6A14V with solid carbide tool was developed and comparison between experimental results and predicted results was discussed. The results showed that the proposed mathematical model can help to predict three-dimensional cutting force under the tool wear effect with high accuracy.Cutting temperature is another important parameter in cutting process. For milling, the intermittent cutting process is more complex and machining environment is worse than turning process. Tool wear is generated under high temperature and high pressure. First of all, the heat transfer model of the cutting zone temperature field considering tool wear effect was established based on the classical heat conduction theory. The temperature fields of shear heat source, tool/chip and tool/workpiece heat source were obtained with heat source method. The temperature model in milling was established by means of discretization thought. After the calibration of nonstandard thermocouple consisted of Ti6A14V and constantan, the experimental study to measure cutting temperature in milling Ti6A14V utilizing semi-artificial thermocouple was presented. The predicted and experimental results for milling process were presented and compared. The results showed that the proposed mathematical model could predict cutting temperature with high accuracy.Tool wear can occur easily under the coupling effect of cutting force and cutting heat in milling titanium alloy. The cemented carbide tool wear mechanism was discussed through a lot of experimental phenomena. The element diffusion effect on the variation of physical properties of cemented carbide tool was obtained based on the variation of microstructure, chemical composition and physical property. The thermo-mechanical coupling effect for carbide tool wear was discussed and the tool wear model was proposed based on Fick diffusion laws. And tool wear subroutine written by FORTRAN is embedded into the finite element software AdvantEdge utilizing secondary development technology. Titanium alloy Ti6A14V material constitutive relation model, the material failure model and tool/chip friction model were determined. Finally, the validity of the model was verified by comparing the simulation results obtained from the secondary development of AdvantEdge simulation software with the experimental results.