The formation of saw-tooth chips is one of the primary characteristics in the machining of hardened steels with geometrically defined cutting tools. Catastrophic failure within the primary shear zone during saw-tooth chip formation is usually attributed to either cyclic crack initiation and propagation or to the occurrence of a thermo-plastic instability. The results presented here show that the primary instability resulting in the formation of saw-tooth chips is initiation of adiabatic shear at the tool tip and propagation partway towards the free surface. Depending on the work material hardness and cutting conditions, catastrophic failure within the upper region of the primary shear zone occurs through either ductile fracture or large strain plastic deformation. Prior to the onset of chip segmentation, which occurs with increases in work material hardness and cutting speed, there is a transition in the morphology of the free surface of continuous chips, from the familiar lamellar structure to what has been termed a “fold-type” structure. This transition is attributed to the operation of thermally softened micro-shear zones, which, it is suggested, are a precursor to adiabatic shear initiation.
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August 2002
Technical Papers
The Mechanisms of Chip Formation in Machining Hardened Steels
John Barry, Research Engineer,
John Barry, Research Engineer
Department of Mechanical Engineering, University College Dublin, Ireland
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Gerald Byrne, Head of Department
Gerald Byrne, Head of Department
Department of Mechanical Engineering, University College Dublin, Ireland
Search for other works by this author on:
John Barry, Research Engineer
Department of Mechanical Engineering, University College Dublin, Ireland
Gerald Byrne, Head of Department
Department of Mechanical Engineering, University College Dublin, Ireland
Contributed by the Manufacturing Engineering Division for publication in the JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING. Manuscript received Aug. 2000; Revised July 2001. Associate Editor: M. Elbestawi.
J. Manuf. Sci. Eng. Aug 2002, 124(3): 528-535 (8 pages)
Published Online: July 11, 2002
Article history
Received:
August 1, 2000
Revised:
July 1, 2001
Online:
July 11, 2002
Citation
Barry, J., and Byrne, G. (July 11, 2002). "The Mechanisms of Chip Formation in Machining Hardened Steels ." ASME. J. Manuf. Sci. Eng. August 2002; 124(3): 528–535. https://doi.org/10.1115/1.1455643
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