International Journal of Mechanical Sciences 77(2013)30–39

Comparison of tool–chip stress distributions in nano-machining of monocrystalline silicon and copper
Chunhui Ji,  Jing Shi* , Zhanqiang Liu , Yachao Wang

Abstract:  Tool–chip interface is a critical zone for machining processes, and the interaction between work material and tool governs chip formation and affects cutting performances.To investigate the tool–chip stress distribution and friction phenomenain nano-machining of monocrystalline silicon and copper materials,
a moleculard ynamics simulation approach is adopted.TheTersoff potential function is employed to
model the interatomic force among silicon atoms,and an EAM potential function is used to model the
inter atomic force between copper atoms.Twelve cases of 3D orthogonal machining with various cutting
conditions are simulated.The stress distributions along the tool–chip interface in copper and silicon
machining are in estigated and compared at various cutting speeds (10–400m/s) and with two tool rake
angles (-15^o and -30^o). Also the effect of depth of cut on the friction behaviors in silicon machining is
investigated at three levels of depth of cut.The results show that the main deformation mechanism of
silicon machining is the amorphous phase transformation,while the machining process of copper is
dominated by the plastic deformation in volving the generation and propagation of dislocations. Under
the same machining parameters,the contact lengths of tool–chip interface are close for the cases of
silicon and copper machining at the initial stage,but they are constantly longer for copper machining
beyond the initial stage. Along the tool–chip interface, the normal and friction stress distributions are
more complex in silicon machining than those in copper machining, and the material flow near tool edge
could be downwards instead of upwards.The patterns of stress distributions in copper machining are not
influenced significantly by the cutting speed and tool rake angle, but those in silicon machining show
significant variations and thus are less conclusive.The results also indicate that the well-established

friction models for conventional machining may not work for

nano-machining.

Keywords: Stress distribution, Nano-machining,  Molecular dynamics simulation,  Copper,  Silicon,  Friction

2013-Comparison of tool–chip stress distributions in nano-machining of monocrys.pdf