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Thesis (Ph. D.)--Ohio State University, 2007.

Thesis (M. S.)--Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Wang, Youjiang; Committee Co-Chair: Jacob, K.I.; Committee Member: Aneja, A.P.; Committee Member: Garmestani, Hamid; Committee Member: Thio, Yonathan S.; Committee Member: Yao, Donggang

A visco-elastic-plastic mathematical model developed at Sheffield City Polytechnic was used to calculate the thermal stress and strain generated during the quenching of an infinite plate of high hardenability steel (835M30) in water, nine experimental oils and a polymer. In.the case of water, previous comparisons between experimental and calculated residual strains was poor. This discrepancy, during the present investigation, was reduced by introducing into the model the relationship between actual surface temperature and surface heat transfer coefficients and by incorporating the effects of various surface finishes into the model. However this discrepancy still remains to a limited extent. The same mathematical model was used to investigate the quenching characteristics of a number of experimental oils: overall the calculatedresidual stresses and strains compared well with the corresponding experimental data. The experimental oilscontained mixtures of additives. Those based on sodiumsulphonate increased the rate of cooling during quenching and the associated absolute residual stresses at a fixed point in the plate. Simultaneously the residual strains were reduced. The use of the succinimide additive produced converse effects in each case. The investigation also included the quenching of plates in polymer solutions of varying concentrations to provide a basis for comparison between the three most commonly used quenchants, viz. water, oil and water soluble polymers. The results indicated that in terms of the residual stresses and strains the oils produced smaller values particularly in the latter case when compared with the polymers. However when compared with water both the oils and water soluble polymers produced significantly smaller residual stresses and strains. The quenching characteristics were also investigated by the use of photography which gave an insight into the cooling characteristics of each quenchant. A water quench produced masses of fine bubbles during the nucleate boiling stage whilst this stage was characterised by large vapour blisters moving up the face of the plate in the case of the experimental oils. Previous photographic evidence indicated that solid polymer was deposited during quench and coated the plate with a gel-like substance which returned back into solution when the temperature was low enough.

The stress-strain behaviour of granular soils under monotonic and cyclic loading conditions and small lateral strains was studied in this work. A simple cubic triaxial apparatus (SCTA), originally developed at Leeds University for monotonic stress-strain studies of sand under controlled and small lateral strains, was used in this investigation. The three principal stresses and strains can be independentLy controlled and measured in this apparatus. The SCTA was modified and further developed to allow cyclic stress-strain studies of granular soils-to be performed. To increase the stress-strain data available on granular soils similar tests to those previously carried out on the medium sand, were performed on fine and coarse sands under monotonic loading conditions. The samples tested were cubic of 150 mm side length and prepared with ranges of initial porosities in a dry condition. To study the cyclic stress-strain behaviour of sand at small strains, a series of new tests on similar cubic samples of the medium sand were performed under cyclic loading conditions. Cyclic loads with different frequencies, amplitudes and number of cycles were applied and the samples were prepared dry at the loosest and densest conditions. Values of the coefficients of active pressure, earth pressure at rest, constrained secant modulus, Young's modulus and Poisson's ratio for the fine, medium and coarse sands were obtained and compared for different conditions. The relationships between vertical and lateral stresses are found and the volume change behaviour of sands in different conditions are studied. Finally some comparisons are made between the results obtained from monotonic and cyclic loading conditions.