The Effect of Prior Cutting Conditions on the Shear Mechanics of Orthogonal Machining

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Abstract
It has been proposed several times in the metal-cutting literature that the machining process is non-unique and that the instantaneous machining conditions depend on the prior machining conditions (e.g. depth of cut, rake angle etc.). To evaluate the validity of this concept, a series of experiments was conducted using a highly accurate CNC machining center. For these experiments, the machining conditions were changed during the course of an orthogonal cutting experiment in a repeatable manner and the measured forces compared as a function of prior history. Tests were conducted on several tempers of 1100 aluminum and commercial purity zinc to evaluate the effect of material properties on the machining response. It was found that the change in measured cutting forces which could be ascribed to prior machining history was less than 3 percent and that material properties, particularly work hardening response, had no discernible effect on the magnitude of the difference.