A photoelastic study of tool stresses caused by unsteady,shear localised chip formations during machining

Abstract

In the high speed machining of metals it has been established that the shearing process is frequently non-uniform resulting in a serrated chip with highly localised shearing. This type of chip formation is promoted solely by the properties of the material being machined and is not initiated by vibrations or resonances of the machine structure. It has been found that this type of unsteady, shear localised chip form can be duplicated when polyethylene is machined at low speeds with araldite cutting tools. By means of a photoelastic technique the variations in tool stress associated with these non-uniform chip forms has been revealed during the machining process. The photoelastic results clearly show that the tool stresses oscillate in a regular manner during the formation of each chip segment. The results obtained have lead to a better understanding of the chip formation process and provide a more complete description of the stress conditions experienced by the cutting tool.

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