Process mechanics of metal cutting with edge radiused and worn tools.

Literature in Manufacturing Research was found wanting of information pertaining to machining forces in orthogonal cutting in the light of a wear-land and edge radius on the cutting tool, the technological implications of which could be enormous. This work attempts to achieve a comprehensive study of the influence of edge condition on the forces on the cutting tool. The Quasi-continuum upper bound plasticity technique, Elastic Contact Mechanics and the Slip Line Field Technique are employed in the modeling efforts. Results from the high magnification video microscopy while machining pure zinc indicated the absence of the molecular or material size effect, preservation of physical similarity and annihilation of geometrical similarity. Though only the Type-II (Continuous without built-up Edge) chip is under investigation in this dissertation, for some materials such as cartridge brass, the movies indicate the formation of stagnant dead metal cap covering the edge radius, which, unlike built-up edge, is stable. The work on corner radiused tools indicates the existence of a critical corner radius that mitigates flank wear on the tool. Corner radii higher and lower than this critical radius tend to increase wear due to thermal load distributions that concentrate heat around the cutting edge. The elastic contact mechanics model indicates that the amount of elastic recovery of work material to either side of the wear land is negligible. The orthogonal tool wear cutting tests show a decrease in machining forces is possible for a freshly radiused tool until the wear land reaches about 4--5 times the edge radius, for a zero rake tool. Thereafter, machining forces increase with wear land length. This effect, that is called the sharpening effect here, is supported by results of another experiment. These experiments show a force decrease that follows the same exponential decay pattern as is observed in the straight-edged orthogonal tool wear experiments. These force data, along with chip thickness and previous observations of Warnecke (1977), are motivators for a slip line field model for the case of a worn, edge-radiused tool. The structure of the model and the requisite theory for this problem has been gathered and is detailed.Ph.D.Applied SciencesIndustrial engineeringMechanical engineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/123217/2/3068905.pd