Study of the minimum depth of material removal in nanoscale mechanical machining of single crystalline copper

It is widely believed that the minimum depth of material removal of single crystalline workpieces is one single atomic layer in nanoscale mechanical machining. However, direct evidence for this is still lacking. In this work the minimum depth of material removal of single crystalline copper in nanoscale mechanical machining is investigated through nanoscratching using molecular dynamics simulations. We demonstrate that the minimum depth of material removal of copper workpiece can achieve a single atomic layer under certain machining conditions in nanoscale machining process. It is found that the minimum depth of material removal is closely associated with the crystal orientation and scratching direction of copper workpiece. Our results also demonstrate that even when the depth of material removal is a single atomic layer of copper workpiece under certain machining conditions, the workpiece material is not removed in a layer-by-layer fashion, which rejects the hypothesis that single crystalline metal materials can be continuously and stably removed one layer of atoms after another in nanoscale mechanical machining. These understandings not only shed light on the material removal mechanism in nanoscale mechanical machining but also provide insights into the control and optimization of nanoscale machining process.