THERMAL EXPANSION BEHAVIOR AND ANALYSIS FOR ALUMINUM-SILICON EUTECTIC ALLOYS AND THE COMPOSITE MATERIAL SYSTEMS: ALUMINUM - SILICON-CARBIDE AND ALUMINUM-TUNGSTEN.

摘要

Analytical solutions have been obtained for the thermal stress and strain of both concentric spheres and concentric cylinders comprised of dissimilar materials. Previously derived formulations for elastic interactions between the materials have been extended to include a plastically deforming shell for both the spherical and cylindrical models. The work hardening has been approximated by a linear stress-strain response of the shell material. Purely elastic response is assumed for the core material. Strain calculations over a given temperature range allow the linear expansivity ((alpha) = 1/L(,o) (DELTA)L/(DELTA)T) to be calculated. Solutions using the developed equations have been carried out using temperature dependent thermal properties.; Thermal expansion measurements have been performed on Al-Si alloys, aluminum alloy silicon carbide composites and aluminum alloy-tungsten composites. These measurements include detailed observations on heating and cooling over repeated temperature cycles between room temperature and 500(DEGREES)C. Changes in the expansivity have been observed in various temperature intervals that cannot be related to volume fraction rules of mixtures or to composite theory based on purely elastic behavior of the materials.; The models developed, in part, relate the differences in the observed expansivity between heating and cooling to plastic deformation of the shell material. The differences in expansivity between heating and cooling result in linear changes in dimensions after thermal cycling.