Date of Award

Winter 2008

Project Type

Dissertation

Program or Major

Mechanical Engineering

Degree Name

Doctor of Philosophy

First Advisor

Brad L Kinsey

Abstract

The products of miniaturization, such as mobile phones, personal digital assistants, computers and other electronic devices have become an indispensable part of our daily lives. Nowadays, more and more industrial products including some medical and electromechanical products contain micro scale metal parts such as connector pins, resistor caps, screws, contact springs and chip lead frames. Miniaturization brings the challenge of realizing the production of these microscale metals parts. Microforming, due to its well known advantages of high production rates, excellent material utilization, and low costs, is a promising manufacturing method compared to the alternative processes in this field. However, well-established conventional, macroscale metal forming processes can not simply be miniaturized without considering possible size effects.

The goal of this research was to determine if deformation size effects occur with miniaturization. Both deformation size effects with respect to specimen size and grain size were considered through the investigation of two processes, microextrusion and microbending. In both of these forming processes, deformation gradients are generated through the cross-sections of the specimens. To analyze these deformation size effects, the distribution of the deformation was characterized by micohardness evaluations. In addition for microextrusion, X-Ray pole figure analyses and microstructure analyses were also performed.

For both processes, the deformation distribution through the cross sections of the fine grained specimens is not affected significantly by the specimen size (i.e. deformation distribution is independent from the specimen size) since the hardness profiles for the all specimen sizes are similar. However, as the specimen size is miniaturized, the deformation distribution of the coarse grained specimens deviates from the fine grained ones, and from the larger size specimens. In addition, as the specimen size decreases the coarse grained specimens have higher hardness increase values at the central region compared to fine grained specimens. This occurs due to the penetration of deformation from highly strained outer regions to the less strained inner regions (or expansion of the highly deformed regions).

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