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

Flank wear of edge-radiused cutting tools under ideal straight-edged orthogonal conditions

Understanding the effects of tool wear is critical to predicting tool life, the point at which tool performance, in terms of power requirement, dimensional error, surface finish, or chatter, is no longer acceptable. To achieve the long cuts that are required for wear testing while maintaining a clear view of the basic process geometry effects, ideal straight-edged orthogonal conditions are realized in a bar-turning arrangement by employing a specially designed two-tool setup. The data show that increasing edge radius tends to increase wear rate, especially at the initial cut-in wear phase. The data also show that when the uncut chip thickness is less than or equal to the edge radius, forces actually decrease substantially with flank wear until most of the edge radius has been worn away. At that point the forces begin to increase with flank wear in a power-law fashion. This decreasing-then-increasing trend is a result of the parasitic (non chip removing) wear-land force increasing more slowly than the chip-removal force is decreasing. The decrease in chip-removal force with an increase in flank wear results from the blunt edge being effectively sharpened as it is removed by the growing wear land. An empirical model structure is formulated, guided by specific elements of the data, to well represent the force trends with respect to wear and edge radius and to assist in their interpretation. The edge-sharpening concept is further supported by a special experiment in which the edge is sharpened without the presence of the wear land. Copyright © 2002 by ASME

The effects of corner radius and edge radius on tool flank wear

The use of cutting tools with a honed edge radius to protect the cutting edge from chipping is ever increasing. The basic understanding of the fundamental cutting mechanics in the presence of an edge radius is increasing as well. The present state of knowledge leads one to question how edge-radiused tools behave under conditions that are more practical than straight-edged orthogonal cutting. Presented here is a study of the interaction of edge radius with corner radius, the latter of which is commonly seen in turning, boring, and face milling processes. Turning test data show that tool flank wear can be minimized for up-sharp tools by using a moderate corner radius. For tools with an edge radius, a wear-minimizing corner radius still exists but is higher than for up-sharp tools. Physical interpretations of these direct and interaction effects are presented

Flank wear of edge-radiused cutting tools under ideal straight-edged orthogonal conditions

Understanding the effects of tool wear is critical to predicting tool life, the point at which tool performance, in terms of power requirement, dimensional error, surface finish, burring, or chatter, is no longer acceptable. To achieve the long cuts that are required for wear testing while maintaining a clear view of the basic process geometry effects, ideal straight-edged orthogonal conditions are realized in a bar-turning arrangement by employing a specially designed two-tool setup. The data show that increasing edge radius tends to increase wear rate, especially at the initial cut-in wear phase. The data also show that when the uncut chip thickness is less than or equal to the edge radius, forces actually decrease substantially with flank wear until most of the edge radius has been worn away. At that point the forces begin to increase with flank wear in a power-law fashion. This decreasing-then-increasing trend is a result of the parasitic (non chip removing) wear-land force increasing more slowly than the chip-removal force is decreasing. The decrease in chip-removal force with an increase in flank wear results from the blunt edge being effectively sharpened as it is removed by the growing wear land. An empirical model structure is formulated, guided by specific elements of the data, to well represent the force trends with respect to wear and edge radius and to assist in their interpretation. The edge-sharpening concept is further supported by a special experiment in which the edge sharpening effect is studied in the absence of wear land