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published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

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This study is concerned with a thermo-elasto-plastic continuum in which the thermodynamic coupling between material deformations, heat generation and flow are included. The elasto-plastic behavior is represented by a linear "rate-type" theory and restricted to infinitesimal deformations. The heat flow equations are posed in incremental form for the linear theory of heat conduction. The theory is such that the conservation laws of thermodynamics are satisfied. A displacement formulation is used and the field equations are shown to be linear operator equations. The operators are tested for symmetry and positive-definiteness in order to test their suitability for solution by a variational method. It is shown that the special case of thermo-elasticity may be solved by minimisation of a functional and that convergence of approximate solutions may be predicted. In the general case of thermo-elasto-plasticity, the operator is shown to be unsymmetric. Therefore an iterative functional is introduced in order to obtain a solution by a variational method. Approximate solutions to some illustrative problems are found using a finite-element-formulation, and it is shown that the results are consistent with expected physical behavior. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

The accurate determination of wear metals in lubricating fluids is of great potential value in the proper maintainence of all types of machinery. Savings of both time and money have been reported in the military and civilian sectors following the implementation of routine wear metal screening in lubricating oils. Current methods are known to discriminate against metals present in the form of particulates. The first part of this dissertation focusses on the direct determination of wear metals in lubricating oils by atomic emission spectroscopy utilizing an inverted inductively coupled plasma as a source. Data are presented which show the effects of power and viewing position on the signal intensity of a variety of sized iron particulate samples in lubricating oil. The second part of this dissertation describes the characterization of a relatively new spectroscopic source--the dual inductively coupled plasma (DICP). The DICP increases the residence time of the analyte in the source by extending the physical length of the plasma discharge and providing two energy deposition regions. Emission intensity, electron density, ion-to-atom intensity ratios, and calculated temperatures are used to compare the DICP with standard inductively coupled plasmas recorded in the literature.

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Although metal fatigue has been recognized for many years and during that time many persons have tried to find the explanation for it, there is still not a complete theory concerning this phenomenon. Metal fatigue is one of the major problems the modem designer must face. If the design techniques are to progress as other technological advances are made, it is evident that it will involve a better understanding of metal fatigue.

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