ON MECHANICS OF UNSTEADY CUTTING PROCESS WITH VARYING UNDEFORMED CHIP THICKNESS : 3RD REPORT : INFLUENCES OF STRAIN HARDENING OF WORK MATERIALS

概要

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Experiment of milling process, which is an unsteady cutting process with varying undeformed chip thickness, is carried out by using annealed and rolled aluminium, copper and 7 : 3 brass as work material. Effects of the strain hardening on the cutting process are discussed. When cutting the metals such as aluminium and copper having a low yield point and a high strain hardening characteristic, multiple patterns of cutting force variation may appear. This phenomenon is considered to result from the transitional period in an initial cutting process being very long for these materials, and cutting energy decreasing remarkably when the ratio of the depth of work hardened layer to the undeformed chip thickness exceeds the critical value. This becomes more conspicuous when a large rake angle tool is used. The above inference is confirmed by the measurements both of the cutting force of a special workpiece to eliminate the hardened layer by annealing, and of the hardness distribution on subsurface of workpiece.