Abstract
In this thesis, research is described in which suspensions of small, solid, spheres were sheared in a Ferranti-Shirley cone and plate viscometer, a method having been developed enabling the particle distribution present in the cone plate gap to be viewed in conditions identical to those present during viscosity measurments. Observations made with this apparatus indicate, that when the particles are suspended in a non-newtonian, normal force producing material, (Poly-iso-Butylene solution) the particles migrate rapidly to the edge of the cone-plate gap. Comparative observations on suspensions of particles in newtonian, and non-newtonian materials having little or no normal force effects, have been made, which do not show any similar radial motion. The observations were recorded photographically and the records analysed to give quantitative data concerning the rate of migration of the particles, and certain particle formations (rings), which developed during the shearing process. A theoretical explanation of the phenomemena has been sought in terms of the effect, upon an individual particle, of the gradient of normal stress known to exist in a normal force producing material, when sheare in a cone and plate instrument. In order to apply the theory to the observed particle radial motion,it was necessary to measure the viscous resistance experienced by a particle moving through a medium, which was itself being sheared in a plane perpendicular to the particles' direction of motion. Measurments were made on particles, falling under gravity in a coaxial cylinder apparatus to establish a value for this viscous resistance,which was then applied to the analysis of particle motion in the cone plate system. Using this data, the predictions of the theory have been evaluated, and compared with the results of observations of particle radial motion made in practice, some measure of agreement having been obtained.