Research On The Chip Formation Mechanism And Tool Wear Of Titanium Alloy Thin-walled Workpiece In High Speed Milling

High speed milling was widely used in aerospace, auto industry and so on with the rapid development of mechanical manufacturing. The serious problem was improving the efficiency and quality of milling. As a typical hard processing material, the low processing efficiency of titanium restricted the development of aerospace industry seriously. Serrated chip was easily generated in high speed milling titanium alloy thin-walled workpiece. Serrated chip leaded to milling force fluctuation, tool system vibration, workpiece surface quality deterioration and tool wear increase. Therefore, research on serrated chip formation mechanism of titanium alloy thin-walled workpiece in high speed milling contributed to understand the nature of high speed milling, improve titanium alloy parts surface quality, milling efficiency and tool life.Combination of theoretical and experimental method was used in this thesis to research serrated chip formation mechanism and tool wear of titanium alloy thin-walled workpiece in high speed milling. The main contents are as following:(1) Serrated chip critical condition was researched theoretically and theoretical formula of serrated chip critical condition was derived on the basis of parallel shear model. Then, serrated chip geometry was characterized and theoretical formula of serrated chip size was derived. Lastly, theoretical formula of serrated chip adiabatic shear band space was derived.(2) High speed milling titanium alloy thin-walled workpiece was conducted. Chip macroscopic morphology was observed and milling force was measure in different milling parameters. Influence laws of milling parameters on macroscopic morphology and milling force were summarized.(3) Scanning electron microscopy was used to observe micromorphology of free surface, back surface and longitudinal section of chips. Metallographic microscope was used to observe adiabatic shear band. Influence laws of milling parameters on micromorphology and adiabatic shear band of chips were summarized.(4) Microhardness tester was used to test microhardness of chips longitudinal section. Influence laws of milling parameters and adiabatic shear on microhardness of chips longitudinal section were summarized.(5) Variation of chips length and width with milling parameters was researched. It could reflect effects of milling parameters on tool wear. Then, scanning electron microscopy was used to observe the tool wear morphology. Wear mechanism of coated carbide tool was analyzed in high speed milling titanium alloy. This could provide certain reference for tool optimization design.