Conventional cutting fluid serves both as a coolant and lubricant. In cryogenic machining, liquid nitrogen
(LN2) is recognized as an effective coolant due to its low temperature; however, its lubrication properties
are not well known. The focus of this study was to investigate how the friction between the chip and the
tool is affected by focused jetting LN2 to the cutting point in machining Ti–6Al–4V. Results of cutting
force measurements indicated that the cold strengthening of titanium material increased the cutting force
in cryogenic machining, but lower friction reduced the feed force. A mathematical model was developed
to convert the measured 3D forces in oblique cutting into the normal and frictional force components on
the tool rake face, and then to calculate the effective friction coefficient. It was found that the friction
coefficient on the tool–chip interface was considerably reduced in cryogenic machining. Increased shear
angle and decreased thickness of the secondary deformation zone, findings from a chip microstructure
study, offer further evidence that friction is reduced. 2001 Elsevier Science Ltd. All rights reserved.
Conventional cutting fluid serves both as a coolant and lubricant. In cryogenic machining, liquid nitrogen(LN2) is recognized as an effective coolant due to its low temperature; however, its lubrication propertiesare not well known. The focus of this study was to investigate how the friction between the chip and thetool is affected by focused jetting LN2 to the cutting point in machining Ti–6Al–4V. Results of cuttingforce measurements indicated that the cold strengthening of titanium material increased the cutting forcein cryogenic machining, but lower friction reduced the feed force. A mathematical model was developedto convert the measured 3D forces in oblique cutting into the normal and frictional force components onthe tool rake face, and then to calculate the effective friction coefficient. It was found that the frictioncoefficient on the tool–chip interface was considerably reduced in cryogenic machining. Increased shearangle and decreased thickness of the secondary deformation zone, findings from a chip microstructurestudy, offer further evidence that friction is reduced. 2001 Elsevier Science Ltd. All rights reserved.
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