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TECHNICAL PAPERS

A Model for the Contact Conditions at the Chip-Tool Interface in Machining

[+] Author and Article Information
B. Ackroyd, S. Chandrasekar, W. D. Compton

Center for Materials Processing and Tribology, School of Industrial Engineering, Purdue University, West Lafayette, IN 47907-1287

J. Tribol 125(3), 649-660 (Jun 19, 2003) (12 pages) doi:10.1115/1.1537747 History: Received March 26, 2002; Revised July 01, 2002; Online June 19, 2003
Copyright © 2003 by ASME
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References

Figures

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Classification of the rake face zones proposed by (a) Doyle et al. 9 and (b) Madhavan et al. 1119
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Orthogonal cutting arrangement with a linear drive actuator
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Schematic of sapphire tool and optical path used for direct observation of the chip-tool interface
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SEM image of the cutting edge of a sapphire tool used in the experiments
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Selected frames from a high speed image sequence showing evolution of the chip-tool contact at Vc=1 mm/sec (a) initial contact between tool and chip resulting in an “incipient” chip (t=0.2 sec;d=0.2 mm) (b) steady state length of the intimate contact zone with RR as its boundary (t=1.3 sec;d=1.3 mm) (c) initiation of metal transfer onto the rake face at arrow D near the boundary of the chip-tool contact (t=5.8 sec;d=5.8 mm) and (d) growth of the region of metal transfer (t=17.8 sec;d=17.8 mm). The time, t, and length of cut, d, corresponding to each image are listed. CC is the cutting edge.
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Selected frames from a high speed image sequence showing evolution of the chip-tool contact at Vc=10 mm/sec (a) initial contact between tool and chip resulting in a chip (t=0.03 sec;d=0.3 mm) (b) intimate contact region at the chip-tool interface below AA(t=0.36 sec;d=3.7 mm) (c) formation of metal deposits near boundary of the chip-tool contact (t=1.20 sec;d=12.0 mm) and (d) division of intimate contact region into sub-regions above and below BB(t=4.87 sec;d=48.7 mm). Asperities such as the one shown at Q are typically seen moving above BB while it is difficult to resolve such asperities below BB. The time, t, and length of cut, d, corresponding to each image are listed. CC is the cutting edge.
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Selected frames from a high speed image sequence showing evolution of the chip-tool contact at Vc=500 mm/sec (a) (t=0.002 sec;d=1 mm) and (b) intimate contact zone at various stages of its evolution to steady state. The bright region in (b) is due to the chip underside and high chip curl (t=0.034 sec;d=17 mm), (c) intimate contact zone at steady state with boundary AA(t=0.074 sec;d=37 mm) and (d) division of intimate contact zone into sub-regions above and below BB(t=0.098 sec;d=49 mm). Asperity movement can be seen above BB. Note the almost complete absence of material transfer near the boundary AA of the chip-tool contact at this cutting speed in contrast to the lower cutting speeds. The time, t, and length of cut, d, corresponding to each image are listed. CC is the cutting edge.
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Two frames from a high speed image sequence showing retarded movement of an asperity (at arrow A) at the chip-tool interface near the cutting edge. Also seen in the frames is a narrow light band of stationary material near the cutting edge that corresponds to a “stagnation” zone. The time, t, of cutting is listed below each image. CC is the cutting edge. Vc=5 mm/sec, rake angle=−5 deg: (a) t=8.60 sec; and (b) t=9.27 sec.
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Two frames from a high speed image sequence showing movement of an inhomogeneity (at arrow I) on the underside of the chip not in contact with the tool rake face. Analysis of such inhomogeneities is used to determine the velocity of the bulk of the chip material. This velocity is referred to as the bulk chip velocity. The time, t, is listed below each image. CC is the cutting edge. Vc=5 mm/sec, rake angle=−5 deg: (a) t=3.27 sec; and (b) t=3.94 sec.
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Optical microscope images of the rake face of a sapphire tool after cutting is completed at (a) Vc=1 mm/sec and (b) Vc=10 mm/sec . Regions of irregular metal deposits can be seen near the boundary of the chip-tool contact. The extent of these regions is less at Vc=10 mm/sec. The dark region immediately adjoining the cutting edge in both the figures is the region of intimate chip-tool contact. There is no discernible metal transfer in this region. Note the similarity between these images and the in situ images of the rake face taken at the same cutting velocities in Figs. 5(d) and 6(d).
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Optical microscope images of the rake face of an aluminum tool after cutting is completed at (a) Vc=1 mm/sec and (b) Vc=10 mm/sec. Note the similarity with the images of the rake face of the sapphire tool shown in Fig. 10.
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Model of chip-tool contact conditions derived from the observations

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