Analysis of stresses during exit in interrupted cutting with champfered tools

This paper presents an analysis of the stresses in the workpiece and tool during exit in interrupted cutting with chamfered tools. An elastic-plastic finite element model is developed to examine the stress fields in the workpiece for various chamfer forms and exit angles. Eight different cases are considered. The workpiece material considered is low carbon steel (203.4 N/mm2 yield stress). The geometric conditions considered include cases where the thickness of the cut h1 is rather small (h1 = 0.04 mm) compared to the chamfer width (Lc = 0.2 mm), as well as cases where Lc = h1 = 0.3 mm. Chamfer angles of 5 and 20° are considered, while the exit angle is taken as 60 and 90°. For the various conditions considered, the loads on the tool are obtained and then used to analyze the stresses in the tool nose. An elastic, plane-strain finite element model is developed for the tool with a very fine mesh near the cutting edge. The material of the tool carbide inserts is considered to be homogeneous and isotropic.The results indicate that the presence of the chamfer does not prevent the dangerous rotation of the workpiece shear angle in the negative direction. For the cases where the thickness of the cut is small compared to the chamfer width (Lc = 5h1), the magnitude of the shear stresses near the cutting edge increases significantly when the chamfer angle is increased from 5 to 20°, and also these stresses reach levels corresponding to the shear flow strength of sintered carbides. For the cases where the thickness of cut is equal to the chamfer width, the results suggest that the build up material which is formed on the chamfer decreases the probability of tensile failure in the tool.