Study On Mechanical Behavior In Hsc

High speed cutting (HSC) technology, which have main feature of higher cutting efficiency and higher machined surface quality, has been pay attention in developed industrial countries,and obtained good economic and social benefits. However, HSC technology had been carried out relatively late at our country, and the research on basis of theory and technology for HSC are less than other overseas. As a result, there are still many problems which restrict the application and development of high-speed cutting technology.High-speed cutting process is a complex dynamic process, involving elasticity, plasticity, fracture mechanics, thermodynamics and tribology. Compared with traditional cutting process, the mechanical behavior of high-speed cutting process has different characteristics and rules. To explore the nature of mechanical behavior during high-speed cutting process under the guidance of materials science, mechanics and modern cutting theory, the dynamics of chip formation, HSC tribological behavior and thermo-mechanical coupling behavior were carried out systematically in order to reveal tool wear behavior and machined surface formation characteristics during HSC by experimental research, theoretical analysis and numerical simulation which supply high-speed hard cutting tool design and processing optimization theory with theory basis.In the high-speed orthogonal cutting experiments with different hardness of 45 steel, using SEM photos of three-dimensional chip morphology and metallurgical photos, study the physical mechanism of cutting chip formation and morphology transforming during high-speed cutting. The researching results showed that workpiece hardness and its performance is the most important factor to determine the characteristics of chip formation and shape; when the 45 steel workpiece hardness is greater than 36HRC, the chip morphological occurs change. When the workpiece hardness and its performance is determined, the cutting speed and feed rate mainly affect chip formation characteristics, with the increase in cutting speed, cutting process chip from the strip chip into a saw-tooth chip, chip thickness reduced, increasing the degree of saw-tooth, or even the formation of the cell chip broken off. Using acoustic emission of chip formation process, study the dynamic effects of cutting force, the results show that the segmentation frequency of saw-tooth chip linear increases with cutting speed during chip formation process, The tool-chip interface contact length for high-speed cutting of 45 steel is researched systematically. Based on the experimental study, in a wide range of cutting speed and feed rate, the contact length model of tool-chip interface for high-speed cutting 45 steel is established. The results showed that tool-chip interface contact length is about 1.5 to 4 times of the cutting thickness, and the contact length and chip thickness ratio (lc/ac) with the cutting speed and feed rate of increase gradually decreased. Adhesive contact area of tool-chip interface is relatively small during high-speed cutting, and gradually decreased with increased cutting speed. The sliding friction coefficient is always greater than the average friction coefficient in chip interface.Based on Merchant's cutting equation, the shear angle calculation equation for high-speed cutting 45 steel in a wide range is established by experimental study of shear angle and friction coefficient during high-speed cutting 45 steel, which consider synthetically cutting speed and feed rate to influence on shear angle.Based on orthogonal cutting experimental results, the cutting force during high-speed cutting different hardness 45 steel is studied systematically, which workpiece hardness, cutting parameters to impact cutting force is analyzed. Generation and distribution of cutting heat , cutting temperature and thermo-mechanical coupling problem is researched during high-speed cutting process, On the basis of J-C constitutive model, the finite element model based on the workpiece hardness was established, and simulated chip formation, cutting force and cutting temperature during high-speed orthogonal cutting different hardness 45 steel, and compared with experimental results. The tool wear behavior and the machined surface characteristics are researched during CBN tool high speed turning hardened 45 steel. CBN cutting tool wear mechanism during high-speed turning hardened is expatiated.