Primary Deformation Zone Research Articles

Influence of strain, strain-rate and temperature on the flow stress in the primary deformation zone in metal cutting

The development of an empirical equation for the flow stress of mild steel in terms of the strain, strain-rate and temperature is described. The equation covers a range of temperature, strain-rate and strain appropriate to the primary deformation zone in metal cutting. The flow stress distribution in the primary zone for normal cutting conditions is obtained and discussed.

A Solution of the Free Oblique Continuous Cutting Problem in Conditions of Light Friction at Chip-Tool Interface

A model for free oblique continuous cutting is proposed. In addition to the hypotheses used in Merchant’s model for free oblique continuous cutting, coincidence of chip-tool friction force with the direction of chip flow on the tool face is assumed; moreover, the deformation process in the primary deformation zone is considered as a case of plane strain. The direction of chip flow is predicted and is found to be function of the cutting conditions. The theoretical predictions compare favorably—less than 10 percent discrepancies—with experimental data published in literature for conditions of low friction at chip tool interface.

On Mechanics of Cutting Process with Varying Undeformed Chip Thickness : 1st Report, Some Considerations on Cutting Mechanics

A basic discussion on an unsteady cutting process, in which the undeformed chip thickness increases or decreases linearly as in peripheral milling, is carried out. In order to make clear a change of the cutting mechanics with a varying underformed chip thickness, the deformation process of a process of a chip formed in previous cutting stage on the tool rake face must be took into consideration. In this paper, a time dependency of cutting energy is analyzed and theoretical equations are derived on the basis of changes in shearing energy in primary deformation zone and frictional energy consumed in tool-chip interface. Numerical solutions of the equations are calculated and compared with experimental results obtained in peripheral milling. A qualitatively good agreement of the variational configurations in both results shows appropriateness of the theoretical analysis. It is also confirmed that a theoretical discussion can interpret the characteristic variation of cutting mechanics in the milling process.

The mechanics of continuous chip formation in orthogonal cutting

On the basis of the experimentally observable processes occurring during the chip formation process, an idealization of the lower boundary of the primary deformation zone in orthogonal cutting is proposed. This boundary is made up of a length L extending from the tool tip in the direction of cutting and a length extending from the extremity of L (remote from tool tip) at an angle of 45° until it intersects the free surface of the workpiece. Using this model and making some simple assumptions regarding the stresses acting on this boundary and the influence of the finite radius of curvature of the cutting edge, relations between the cutting force components and the geometry of the cutting process are deduced. Published experimental data are then shown to be consistent with these relations. The normal stress distribution ahead of the tool is then idealized as a uniformly distributed tension, immediately ahead of the tool, followed by a region of uniform compression and deductions based on these assumptions, are tested using experimental data. The model is then used to account for the features observed when cutting in the presence of built-up edge and explanations of the size effect are offered. The effects of cutting in the presence of cutting fluids are explained in terms of the model and, finally, a parameter reflecting the width of the primary deformation zone is shown to vary with cutting conditions in exactly the same way as does the experimentally measured width. The length L is proposed as an inverse measure of the ductility of the cutting process, the ductility increasing as L decreases. L is shown to be linearly related to the adhesion length, i.e. the length of that part of the tool-chip contact region over which the chip adheres to the rake face.