Ph.D. Proposal Presentation by Sathyan Subbiah
Thursday, October 7, 2004

(Dr. Shreyes N. Melkote, Chair)

"Some Investigations of Scaling Effects in Micro-Cutting"

Abstract

The industry needs economical manufacturing processes to make miniature components required in many applications such as in MEMS, medical devices, and defense. As a manufacturing process, mechanical removal of material (cutting) has been widely used to make macro-sized parts. Thus, many researchers are exploring the applicability of this process to meso/micro-sized parts and have observed and reported differences between macro-scale cutting (>500 µm) and micro-scale cutting (0.1-500 µm). Principal among the differences is in the energy supplied for micro-cutting and its subsequent distribution among various aspects of cutting. As the uncut chip thickness is decreased, the specific cutting energy is seen to increase. Also, the literature shows evidence of scaling effects in sub-surface plastic deformation and in the amount of energy expended in this, with reduction in uncut chip thickness. Hence, the focus of this work is to develop fundamental understanding of some of the factors contributing to the behavior in specific cutting energy, while providing some explanations for the sub-surface plastic deformation in micro-cutting.
The research plan consists of the following: (1) Interpret and analyze specific cutting energy as a ratio of two numbers (2) Perform unique experiments to isolate the constant cutting force component (3) Model the constant cutting force component using dislocation based fracture mechanics (4) Measure energy used in sub-surface plastic deformation under various micro-cutting conditions and confirm the presence of scaling effects in sub-surface plastic deformation, and (5) Provide an explanation for this scaling effect using fracture mechanics based approach.
The significant contribution of this work includes a new approach to viewing size-effect in specific cutting energy and incorporating the various reasons attributed to it from this point of view. Also, isolating, measuring, and modeling a component of cutting force that is independent of uncut chip thickness will provide a better understanding of the size effect in specific cutting energy. The energy used in sub-surface plastic deformation will be measured and explained using the plastic deformation associated with ductile fracture. This is expected to clarify the scaling effect reported in this aspect of micro-cutting.