Knowledge of the stress-strain relationship of the compacted soils in tension is of importance for understanding of cracking that occurs in earth structures, in particular embankment dams and landfill barriers. Understanding the correlation between tensile properties and traditional soil parameters and soil suction is essential in identifying problems associated with desiccation induced cracking. A series of extensive laboratory experiments were performed on three different soils from existing embankment dams. This thesis concentrated on the investigation of tensile strength in relation to the type of soil, compaction water content, compaction density ratio, rate of loading, soil suction, moisture retention characteristics and the effect of drying and wetting. Stress-strain behaviour and tensile properties indicated a dependence on soil type and compaction criteria. The plasticity index, clay content and type of mineral has shown a significant influence on tensile strength. Compaction dry of optimum resulted in an increase in strength. Compaction wet of optimum showed a decrease in strength and small increase in strain at failure. Higher compaction effort resulted in higher tensile strength, tensile stiffness and brittle stress-strain behaviour. Difference in loading rate revealed response time for initial tensile deformation as well as sustainable duration up to failure point. The effect of soil suction plays an important role in drying during which specimens exhibited a considerable strength increase. The magnitude of strength increase may have been contributed by a combination of suction, air entry value and compaction density. The effect of wetting could cause decreasing in suction and thus a reduction in strength. Based on the findings, it was concluded that the desiccation-induced may not necessarily occur due to an associated increase in tensile strength. However, an increase in tensile strength is likely to be accompanied by an increase in shrinkage. Therefore, desiccation-induced cracking is related to the interaction between moisture loss, change in soil suction, tensile stress and shrinkage.

Interbody fusion cages are increasingly used in the treatment of spinal disease and injury in order to stabilize movement and promote arthrodesis of the vertebral bodies, but the micro-mechanics of the interaction between the cage and the adjacent host bone is not fully understood. This information has bearing on post-surgical therapy protocols, prediction of long-term bone tissue changes, and optimization of cage design. In order to gain insight into this problem, functional microCT imaging was used to directly evaluate implant micromotion and full-field vertebral body strains in an animal model implemented with various configurations of BAK interbody cages. It is believed that variations in cage design will produce variable implant success, functional fusion will be related to the extent of implant fixation, and specific strain fields will be associated with fused and unfused samples. We found that samples ranged from completely unfused (implant motion) to fully fused with organized trabecular bone (no motion). Strains concentrated at the implant interface in unfused samples, while fully fused samples exhibited uniformly distributed strains. / Graduation date: 2004

Thesis (M.Eng.)--Memorial University of Newfoundland, 2005. / Bibliography: leaves 113-116.

Ph.D. / Materials science / The influence of resonant and sub-resonant frequency vibration on the longitudinal residual stresses in A-36 mild steel weldments has been studied. Residual stress analysis was carried out using sectioning, x-ray and blind-hole-drilling techniques. The hole-drilling method was modified to take into account the effect of local plastic yielding due to stress concentration and the machining stresses, with a resultant accuracy comparable to that obtained by the sectioning method. As a result of the vibratory treatments, residual stress redistribution occurred near the weld; the peak stresses were decreased by up to 30%. The resonant frequency vibration had a more pronounced stress redistribution as compared to the sub-resonant frequency vibration. Transmission electron microscopy studies indicated local plastic deformation as the mechanism by which this stress reduction occurred. Constant amplitude axial fatigue experiments on samples machined from regions adjacent to the weld showed that both the vibratory techniques did not induce any fatigue damage.

Thesis (M.C.E.)--University of Delaware, 2009. / Principal faculty advisors: Dov Leshchinsky and Christopher L. Meehan, Dept. of Civil & Environmental Engineering. Includes bibliographical references.

Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 190-211).

Thesis--Teknillinen Korkeaukoulu, Otaniemi. / Includes bibliographical references.

Thesis (Ph. D.)--School of Materials Science and Engineering, Georgia Institute of Technology, 2004. Directed by W. Steven Johnson. / Includes bibliographical references (leaves 261-271).

Thesis (Ph. D.)--Lehigh University, 2003. / Includes vita. Includes bibliographical references (leaves 334-335).

Thesis (M. Phil.)--University of Hong Kong, 1972. / Mimeographed.