Theoretical And Experimental Research On Shear Angle, Chip Flow Angle And Tool Condition Monitoring

Metal cutting is a leading machining method in manufacturing industry, and its mechanism research has great directive significance to all kinds of production lines and machining of parts. Metal cutting is a complicated nonlinear deformation process which has been simplified in previous researches. However, the simplified models in previous researches didn’t have good performances to reflect actual cutting process. Further studies of cutting mechanism are still needed to improve prediction results of metal cutting.Shear angle is an important parameter in metal cutting and is almost used in all kinds of cutting calculation. Using the cutting power equilibrium equation V-F=Ws+Wf, a new shear angle prediction model for orthogonal cutting was proposed in the study. The principal cutting force F which can reflect the complicated cutting situation was experimentally measured in the study. By substituting into the cutting power equilibrium equation with the measured value of the principal cutting force F, the prediction model has more accurate prediction than just theoretical derivation without experimental data.Three-dimensional (3D) cutting is a common cutting situation with the main and the minor cutting edge in engagement with workpiece. In this study, RATIO is defined as the ratio of the main to the minor cutting edge length engaged in cutting, and the effect of RATIO on cutting force was first proposed. The research results are in good accordance with qualitative analysis results derived from empirical formula of cutting force. Two prediction models of chip flow angle were proposed for Usui cutting model and helical V grooves turning:the minimum value of the total shear area produced by the two cutting edges was calculated to determine the chip flow direction for Usui cutting model; chip flow angle prediction model was expressed as the transformed cutting power equilibrium equation for V grooves turning. The relation between chip flow angle and the value of RATIO was first studied for the two cutting situations:chip flow angle decreases with the increase of RATIO at the constant equivalent cutting area; RATIO equal to 4 is the turning point before and after which the drop trend of the chip flow angle is different comparatively.Tool wear greatly affects quality of workpiece, machine life and safety of machine operators. In this study, image processing technology was applied to direct monitoring of tool condition by processing tool wear image obtained via endoscopy digital photographic system. Multi-resolution analysis was applied to the analysis of cutting force signals acquired by a turning dynamometer. Using the relationship between wavelet transform modulus maxima and singular point, the signal point location can be analyzed, and the local singularity was described by Lipschitz index. The wearing condition of cutting tool can be acquired by location of singular point and its other information to realize indirect tool condition monitoring. The feasibility of cutting tool wearing detection by wavelet transformation was validated by experiments.Shear angle, cutting force and chip flow angle in 3D cutting were analyzed in this study, and the research results were validated by FEM software and experimental measurement. In addition, tool wear monitoring was investigated in this study. The research conclusions obtained in this dissertation will be very helpful for the further application and studies of metal cutting.