Finite Element Simulation of MNT

The dimensional tolerance achieved by precision machining technology is on the order of 1 nm and the surface roughness is on the order of 0.1 nm. The dimensions of the parts or elements of the parts produced may be as small as 1 μm, and the resolution and the repeatability of the machine used must be of the order of 1 nm (10 nm). Unlike conventional machining processes, precision machining processes are not based on the removing the metal in the form of chips using a wedge shaped tool. When metal is removed by machining there is substantial increasing in the specific energy required with decrease in chip size. Since the shear stress and strain in metal cutting is unusually high, discontinuous microcracks usually form on the metal-cutting shear plane. Owing to the complexity of elasticplastic deformation at nanometer scale, the worldwide convinced precision materials removal theory is not built up until now. As the complexity associate with the precision machining process involve high strains, strain rates, size effects and temperature, various simplifications and idealizations are necessary and therefore important machining features such as the strain hardening, strain rate sensitivity, temperature dependence, chip formation and the chip-tool interface behaviors are not fully accounted for by the analytical methods. Experimental studies on precision machining are expensive and time consuming. Moreover, their results are valid only for the experimental conditions used and depend greatly on the accuracy of calibration of the experimental equipment and apparatus used. Advanced numerical techniques such as Finite Element Method (FEM) is a potential alternative for solving precision machining problems. Characterizing the surface, subsurface, and edge condition of machined features at the precision scale in the FEM analysis are of increasing importance for understanding, and controlling the manufacturing process.

Keywords: Finite element, thermal-mechanical coupling, materials removal criterion, boundary condition, residual stress.