Thesis (Ph. D.)--Ohio State University, 1986. / Includes vita. Includes bibliographical references (leaves 170-179). Available online via OhioLINK's ETD Center.

The possible deformation behaviour of spheres in a compact has been theoretically analyzed and experimentally verified. The change in contact area radius 'a' relative to the particle radius R has been related to the bulk density and bulk strain for four possible modes of packing: simple cubic (Z = 6), orthorhombic (Z = 8), rhombohedral (Z = 12), and body-centered cubic (Z = 8). An equation relating the above parameters can be represented by D — D。= [formula omitted] D。(a/R)² for different types of packings, D and D。 being the densities at any a/R and at a/R = 0, respectively. It has been shown experimentally by deforming monosized lead spheres at room temperature, 50 and 100°C in a cylindrical die, that the overall deformation is similar to that of the orthorhombically packed spheres. A change in the coordination number Z during the deformation process was also observed and may partially account for the deviation from the theoretically predicted values. Similar experiments using sapphire and K-Monel spheres were also carried out in the temperature range 1570 - 1700°C and 800 - 1000°C respectively. The results showed that the deformation behaviour was very similar to that of the lead spheres. A study of the geometry of deformation revealed that most of the spheres deformed in a random manner, although individual colonies of orthorhombic, tetragonal and rhombohedral packings were observed. It was also observed that the deformed faces that were approximately perpendicular to the direction of pressing were about 2.2 times larger than those parallel to the direction of pressing. This observation has been subsequently used to modify the theoretical models. The particle rearrangement and plastic flow have been found to be the predominant mechanisms for the densification of lead, K-Monel, and sapphire spheres under the experimental conditions used in this investigation. The criterion for yielding of two hemispheres of the same material in contact was used to incorporate the yield strength in the basic density equation. This equation has been found to fit the data obtained during the hot-pressing of the spheres. It has been observed that the deformation of sapphire single crystal spheres takes place by a complex deformation process. The presence of the basal and prismatic slip has been identified in the spheres deformed at 1570 and 1700°C. Presence of cross slip is also confirmed by the optical and electron micrographs at these temperatures. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

Particulate, discrete and frictional systems such as sand constitute a separate class of materials. In order to derive stress-strain relations for these materials, their key features have to be identified and incorporated into the theoretical formulations. The presence of voids, the ability to undergo continuous and systematic spatial rearrangement of particles, the existence of bounds for the developed ratio of tangent and normal contact forces and the systematic variations of the tangent and normal contact force distributions during general loading, are identified as key features of particulate, discrete and frictional systems. The contact normal and the contact branch length distribution functions describe the spatial arrangement of particles mathematically. The distribution of contact normals exhibit mutually orthogonal principal directions which coincide with the principal stress directions. Most contacts in frictional systems do not develop limiting friction during general loading. Sliding of a few suitably oriented contacts followed by rolling and rigid body rotations and displacements of a large number of particles is the main mechanism causing non-recoverable deformations in frictional systems. As a part of the rearranging process, dominant chains of particles are continuously constructed and destructed, the rates being different at different stages of loading. A change of loading direction is associated with a change of dominant chains of particles resulting in changes in strain magnitudes. Rate insensitive incremental stress-strain relations are derived here using the principle of virtual forces. The key features of frictional systems have been incorporated into the stress-strain relations following the theoretical framework proposed by Rothenburg(1980), for analysing bonded systems of uniform spherical particles. For frictional systems, the load-deformation response at particle contacts is assumed to be non-linear. The deformations resulting from all internal activity are quantified defining equivalent incrementally elastic stiffnesses in the tangent and normal directions at contacts and defining loading and unloading criteria. After each increment of loading, the incremental stiffnesses and contact normal distribution are updated to account for the changes resulting from rearrangement of particles. Laws that describe the spatial rearrangement of particles, changes in the ratio between the tangent and normal contact force distributions and the resistance to deformation resulting from changes in dominant chains of particles are established based on the information from laboratory experiments reported in the literature and numerical experiments of Bathurst(1985). The stress ratio and the state parameter (defined as the ratio of void ratios at the critical-state to the current state, computed for a given mean-normal stress) are identified as key variables that can be used to quantify the extent of particle rearrangements. The proposed formulations are capable of modelling the non-linear stress-strain response which is dependent on the inherent anisotropy, stress induced anisotropy, density of packing, stress level and stress path. To predict the stress-strain response of sand, a total of 24 model parameters have to be evaluated. All the model parameters can be evaluated from five conventional triaxial compression tests. The proposed stress-strain relations have been verified by comparing with laboratory measurements on sand. The data base consists of triaxial tests reported by Negussey(1984), hollow cylinder tests graciously carried out for the author by A. Sayao, and true triaxial and hollow cylinder tests made available for the Cleveland Workshop(1987). / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

At present the majority of wood-stave pipelines are supported on rigid cradles which bear on the lower 45% of the pipe circumference. The accepted method of analysis, developed by Regnell, completely ignores the stress concentrations induced in the staves just above the cradle tips. In this work, a full ring is proposed to distribute the support reaction to all staves and minimize deflections from a circular profile. From a consideration of equilibrium and stress-displacement relations for a stave element two fourth-order partial differential equations in terms of the radial and tangential displacements of the element are developed. Trigonometric series are applied to their solution. The support ring displacements are similarly described in series form. A study of the compatibility of ring and stave deflections removes the indeterminacy and all stress resultants, as functions of the ring or stave deflections, are then available from back-substitution. The formulas established are sufficiently complex that access to an electronic computer is a great practical advantage. In a numerical example, the effects of modifying the ring stiffness, hydraulic head, and the circumferential stiffness of the stave cylinder are investigated. The non-linear influence of ring and band tensions on the deformed shape of the structure is included. Design considerations are briefly discussed. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

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Master of Science

published_or_final_version / abstract / Civil Engineering / Doctoral / Doctor of Philosophy

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