A REASSESSMENT OF THE EXTRAPOLATION TECHNIQUE FOR DETERMINING PARASITIC CUTTING LOADS UNDER ORTHOGONAL CUTTING IN STRAIN-RATE HARDENING MATERIALS

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Abstract
One suggested procedure for determining parasitic cutting loads is to conduct cutting tests at different feeds, measure the cutting forces, plot the forces as a function of feed and extrapolate the data to zero feed. The intercept obtained at zero feed is identified as the parasitic cutting load. This procedure has been tested against cutting data for zinc and shown to give incorrect results. Further an appreciable non-zero intercept was obtained even when the known parasitic cutting forces were subtracted from the measured data. An analytical assessment of this procedure demonstrates that this procedure is fundamentally incorrect for materials, like zinc, which exhibit high strain rate sensitivity. For materials which are strain rate insensitive however the procedure is valid. The validity of the procedure is essentially insensitive to the work hardening behavior of the work piece.