Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Mechanical and Materials Engineering

Supervisor

Dr. Robert J Klassen

Abstract

Splined Mandrel Flow Forming (SMFF) is a metal spinning operation that involves the application of high multiaxial compressive stress states to invoke large plastic flow in the work piece. This allows for essentially one-step fabrication of complex internally-splined shapes. In this research project, the equivalent plastic strain, invoked throughout bcc (1020 steel) and fcc (5052 and 6061 aluminum alloys, pure copper, and 70/30 brass) samples, that were made by SMFF, was measured. The objective of the research were to measure the to obtain data on the effect of microstructure and mechanical parameters on the flow formability of ductile bcc and fcc metal work pieces. To address this objective the equivalent plastic strain in the high strain regions of the flow formed metal parts were measured with the use of Micro/nano-indentation hardness measurements. Also, micro/nano-indentation tests were performed, on the same alloys the metal alloys which were used in the SMFF experiments, to assess the effect of pre-exist plastic strain, strain rate, and deformation volume on the operative deformation mechanisms. These parameters were found to depend upon the microstructure and the associated deformation mechanisms.

Data from indentations tests at constant loading rate and constant strain rates on a variety of ductile metals/alloys were used to determine the effect of dislocation type (i.e. “statistically stored”, and “geometrically necessary”), stacking fault energy, and activation volume. This accounts for the observed strain rate sensitivity and the depth dependence of the indentation stress. It also affects the local strain magnitude and gradient during the SMFF process. This micro/nano-indentation based test technique allows one to then obtain data from which to validate calculated equivalent plastic strain distributions derived from numerical simulations and, for end users of a metal forming technique, allows one to understand and quantify the mechanical properties of the formed work piece.

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