Modeling of the Tool Edge Radius Effect on the Mechanics of Micromachining

Abstract

The mechanics of tool-based micromachining is significantly different from that of conventional-macro machining due to the tool edge radius effect. Such effect arises in micromachining as the micron-scaled undeformed chip thickness, a approaches the size of the tool edge radius, r of several microns. A predictive cutting model that assumes a perfectly sharp cutting edge yields reasonable agreement with experimental results in conventional-macro machining but such an assumption is not valid in micromachining. However the operating mechanism is not fully understood at present. This thesis presents a fundamental modeling study of the tool edge radius effect in micromachining using an advanced finite element modeling technique. Through the arbitrary Lagrangian-Eulerian (ALE) method, the effects of tool edge radius on the contact phenomenon and plastic deformation behavior of micromachining are elucidated. A thrust-oriented mechanism known as the extrusion-like chip formation mechanism is activated at a critical a/r combination which produces high quality surface finish.