Date of Award

1987

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

First Advisor

Craig S. Hartley

Abstract

A study of hydrostatic co-extrusion of a hard-core/soft-clad bi-metallic compound has been conducted. The research employs the Sachs' boring-out technique to determine the residual stress distribution in a hydrostatically co-extruded copper-clad Gildcop composite. A parallel simulation of the residual stress distribution in such composites extruded to extrusion ratios of 2.25, 4.0, and 7.5 was conducted using the ABAQUS finite element code. The version of the code employed uses an elastic-plastic constitutive law for material behavior and does not simulate deformation heating effects. Data for the mechanical properties were obtained experimentally by constant true strain-rate tests on material identical to that used in the extrusion experiments. The results indicate that the extrusion pressure varies linearly with the natural logarithm of the extrusion ratio. The simulation results obtained for this pressure, however, are generally higher than those found in experiments. Comparison of the experimental and numerical results of the residual stresses indicate that although the two results are qualitatively similar, they are quantitatively different. In all cases, the experimental results were much lower than those of numerical calculations, implying that some recovery has occurred during the extrusion process. The investigation shows, however, that finite element analysis in conjunction with experimental measurements can be applied successfully to predict and verify the qualitative residual stress patterns developed in hydrostatically extruded products.

Pages

154

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