Machining with tool-chip contact on the tool secondary rake face-part I: a new slip-line model

摘要

Given the growing number of applications of groove-type chip breaker tools in modem machining, it is becoming increasingly important to study the tool-chip contact on the tool secondary rake face. This type of tool-chip contact significantly changes not only the state of stresses in the plastic deformation region, but also changes the distribution of forces and temperatures over the tool rake face. A new slip-line model accounting for the tool-chip contact on the tool secondary rake face is proposed in this paper. The model also takes into account chip curl and incorporates seven slip-line models developed for machining during the last six decades as special cases. Dewhurst and Collins's matrix technique for numerically solving slip-line problems and Powell's algorithm of nonlinear optimization are employed in the mathematical formulation of the model. The inputs of the model include (a) the tool primary rake angle γ{sub}1, (b) the tool secondary rake angle γ{sub}2, (c) the tool land length h, (d) the undeformed chip thickness t{sub}1, (e) the ratio of hydrostatic pressure P{sub}A to the material shear flow stress k, (f) the ratio of frictional shear stress τ{sub}1 on the tool primary rake face to the material shear flow stress k, and (g) the ratio of frictional shear stress τ{sub}2 on the tool secondary rake face to the material shear flow stress k. The outputs of the model include (a) the cutting force F{sub}c/kt{sub}1w and the thrust force F{sub}t/kt{sub}1w, (b) the chip up-curl radius R{sub}u, (c) the chip thickness t{sub}2, and (d) the natural tool-chip contact length l{sub}n.