Force System Due to the Presence of Elasto-Viscous Flow Zone during High Speed Machining

During high speed machining a thin non crystalline layer is found to appear between the tool and chip (secondary shear zone) which is known as flow zone, due to melting of chip surface adjacent to the tool face because of high pressure and temperature at the tool chip interface. The nature of flow zone is believed to be elasto-viscous at moderately high cutting speed. In the course of literature survey it was found that the force system during high speed machining has been the subject of many investigations. But none of the present metal cutting theory is capable of predicting accurately what happens to the cutting mechanism/force system, mainly because of the presence of the flow zone at the tool chip interface. It indicates that very little work has been performed during high speed machining and no definite trend has emerged out so far.

The main objective of this paper is to present the theory of cutting forces on the assumption that the secondary shear zone consists of solid material area and the molten area, considering hydrodynamic and momentum effects. This theory explain that the work piece properties and cutting conditions influence the formation of flow zone, which effects the formation of secondary shear flow and hence force system behavior. A new force system which is applicable to high speed machining is developed including momentum and hydrodynamic forces.