Critical cutting thickness in ultra-precision machining of single crystal silicon

This paper makes use of a strain gradient theory to obtain excellent consistency between observed experimental phenomena and theoretical calculations in exploring the brittle–ductile transition mechanism of single crystal silicon (SCS). The critical cutting thickness in the ultra-precision machining of SCS is then derived by means of theoretical calculations. SCS was first subjected to nanoindentation, and it was observed that under a particular scale of deformation, the silicon not only underwent plastic deformation, but more importantly also experienced strain gradient effects. This can be attributed to different types of dislocation motion present in the crystal, suggesting that the plastic deformation of SCS is caused by geometrically necessary dislocations, and that a size effect fulfills the necessary conditions for plastic region machining of SCS. Subsequently, the ability of scale gradient theories to link together microscopic mechanisms with observable mechanical properties was utilized to calculate the critical cutting thickness in the ultra-precision machining of SCS as approximately between 110 and 220 nm, a result which was then verified by experimental means.