| Budget Amount *help |
¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 1994: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1993: ¥2,000,000 (Direct Cost: ¥2,000,000)
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| Research Abstract |
The role of friction in nano-scale machining has been investigated using a new molecular dynamics simulation model based on the Nose-Hoover method, in which the restricted analytical region moves together with the tool advancement. Orthogonal machining of a (111) plane of a copper single crystal by a diamond-like tool with 3 nm edge radius has been simulated, where the uncut chip thickness and the cutting speed was set at 1 nm and 20 m/s, respectively, and the cutting direction was taken to be [101]. Morse type potentials with various magnitudes of the cohesion energy were postulated to approximate the friction at the tool-workpiece interface as well as the materials themselves.The major results obtained are as follows :
(1) Chip formation in the nano-scale metal machining is similar to that observed in macro-scale machining. With increase of the bond energy at the interface, both chip thickness and contact length between the chip and tool become larger, leading to increases in the average cutting forces and the temperature in the system. Besides, the machined surface is subjected to severe damages.
(2) Tool wear has also been modelled by taking into account the tool consisting of the carbon atoms which have a reduced cohesion energy and obey Newton's equation of motion. The atomistic wear proceeds with the repetition of inter-diffusion between the workpiece and tool atoms and re-adhesion of the worn atoms to the tool.
(3) The shape of interface potential and the tool wear distributions also affect the minimum thickness of cut and the depth of the region where the displaced workpiece atoms exist : two and ten atomic layrs are their minimums, respectively.
(4) Existing atomistic defects such as vacancies and dislocations increase the cutting force and enlarge the atomistic disturbance in the workpiece as well, which is due to the interaction between the defects and the dislocations emerging from the cutting edge.
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