-1 were achieved when testing specimens and this rate was obtained using a split Hopkinson pressure bar. A substantial number of preliminary tests were conducted in order to obtain a suitable specimen size which was then used in the temperature measurement process. Quasistatic, intermediate and high strain-rate tests were performed; the last utilised the radiometer for temperature measurement. An Eyring plot was constructed from which fundamental values for activation volumes and enthalpies were obtained. Full descriptions of the testing techniques used have been included and a brief photoelastic analysis has been carried out on a partially deformed specimen which shows molecular alignment.

Low carbon bainitic steels microalloyed with Nb, Ti and V are widely used for the pipeline, construction and automobile industries because of their excellent combination of strength, toughness and weldability. Boron as another major alloying element has been also frequently used in this type of steels since the 1970s. The purpose of adding boron is to improve the hardenability of the steel by promoting bainite formation. / It has been realized that Boron can only be effective as a strengthening element when it is prevented from forming BN and/or Fe23(C, B) 6 precipitates. Therefore, Boron is always added together with other alloying elements which are stronger Nitride or Carbide formers, such as Ti and Nb. However, the formation of complex bainitic structures and the interaction with precipitates at industrial coiling temperature are not adequately understood. / In this study, the effect of boron on the microstructure and mechanical properties of a low carbon Nb-B steel was studied by a hot compression test (50% reduction at 850°C) followed by quenching samples into a salt bath. The microstructures of the tested samples were examined through optical microscopy and SEM; and the mechanical properties of these samples were investigated by micro-hardness and shear punch tests. / The results indicate that during thermo-mechanical controlled rolling (TCR), the final properties of the products not only depend on the applied deformation but also depend on the coiling temperature where phase transformation takes place. According to the investigation, two strengthening mechanisms are responsible for the strength of the steel at the coiling temperature: phase transformation and precipitation. Under optical microscopy, the microstructures of all specimens appear to be bainite in a temperature range from 350°C to 600°C without distinct differences. However, the SEM micrographs revealed that the microstructures at 550°C are very different from the microstructures transformed at the other holding temperatures. / Two strength peaks were observed at 350°C and 550°C in the temperature range studied. It is believed that the NbC precipitates are the main contributor to the peak strength observed at 550°C because the kinetics of NbC is quite rapid at this temperature. The strength peak at 350°C is mainly due to the harder bainitic phase, which formed at relatively lower temperature.

The high speed deformation behavior of a commercially available dual phase (DP) steel was studied by means of split Hopkinson bar apparatus in shear punch (25m/s) and tension (1000s-1) modes with an emphasis on the influence of microstructure. The cold rolled sheet material was subjected to a variety of heat treatment conditions to produce several different microstructures, namely ferrite plus pearlite, ferrite plus bainite and/or acicular ferrite, ferrite plus bainite and martensite, and ferrite plus different fractions of martensite. Static properties (0.01mm/s for shear punch and 0.001s -1 for tension) of all the microstructures were also measured by an MTS hydraulic machine and compared to the dynamic properties. The effects of low temperature tempering and bake hardening were investigated for some ferrite plus martensite microstructures. In addition, two other materials, composition designed as high strength low alloy (HSLA) steel and transformation induced plasticity (TRIP) steel, were heat treated and tested to study the effect of alloy chemistry on the microstructure and property relationship. / A strong effect of microstructure on both static and dynamic properties and on the relationship between static and dynamic properties was observed. According to the variation of dynamic factor with static strength, three groups of microstructures with three distinct behaviors were identified, i.e. classic dual phase (ferrite plus less than 50% martensite), martensite-matrix dual phase (ferrite plus more than 50% martensite), and non-dual phase (ferrite plus non-martensite). Under the same static strength level, the dual phase microstructure was found to absorb more dynamic energy than other microstructures. It was also observed that the general dependence of microstructure on static and dynamic property relationship was not strongly influenced by chemical composition, except the ferrite plus martensite microstructures generated by the TRIP chemistry, which exhibited much better dynamic factor values. This may suggest that solid solution strengthening should be more utilized in the design of crashworthy dual phase steels.

No description available.

The thoracolumbar transversospinal muscles are vital in normal function and are implicated in the pathogenesis of different forms of spinal pathology and pain. They are the target for specific forms of clinical intervention such as exercise regimens and the release of �trigger points�, and are often analysed through imaging studies and electromyographic recordings. Despite the importance of these muscles, there is a paucity of knowledge in regard to aspects of their functional morphology. The aim of this thesis was to examine the thoracolumbar transversospinal muscles between the mid-thoracic spine and sacrum, examining their gross morphology, fibre arrangement, fibre types, and an animal model in order to provide a better understanding of their functional morphology. The gross morphology of these muscles was studied by micro-dissection of cadaveric material. Their form was found to differ from that published in either text book or peer reviewed articles, clearly indicating the existence of a �semispinalis� muscle in the lumbar spine. In addition, the arrangement of these muscles was found to be homologous between the thoracic and lumbar regions, which is contrary to published descriptions. Arrangement of the muscle fibres was examined by identifying motor endplates with acetylcholinesterase histochemistry in all muscles throughout the area of interest. Only one endplate per fibre was observed, and no in-series fibres were found. All muscles showed a complex multipinnate form with large areas of muscle tendon intruding into each muscle. Fibre type proportions in each muscle were investigated by immunohistochemistry. Results indicate the percentage of total muscle area occupied by type I fibres decreased the more caudad the vertebral level of origin, for all muscles. There were significant differences in the area percentage of type I fibres between many different vertebral levels. These differences were mostly found between the most cranial and most caudal levels examined. The percentage of type I fibres recorded suggest all muscles are likely postural in function, and the gradual decrease in type I fibres and the lack of a distinct thoracic / lumbar boundary in the data suggests the thoracic and lumbar transversospinal muscles are homologous. The thoracolumbar transversospinal muscles of the MLC3F nlacZ transgenic mouse were micro-dissected to determine their morphology, and their fibre arrangement subsequently determined using acetylcholinesterase histochemistry. These muscles showed a homogeneous form throughout the thoracolumbar spine, and no in-series muscle fibres were observed with all muscles having one motor endplate per fibre. Results indicated similarities between the morphology of mouse and human transversospinal muscles, perhaps indicative of an adaptation to an upright posture. This thesis provides information that facilitates a more complete understanding of the morphology and function of the thoracolumbar transversospinal muscles. In addition, results indicate that these muscles are homologous through the thoracic and lumbar spine, and therefore the classification and nomenclature used to describe these muscles should be re-examined. Furthermore, the morphological evidence, combined with recent embryological studies, supports the use of the term �spinotransverse� to more accurately describe this muscle group.

Particulate filled polymer composites are gaining growing acceptance in the commodity industry because the properties can be adjusted according to the industry's requirements. As particulate filler, fly ash is ready to compete with other particular fillers in polymer composites industries. Although fly ash is a cheap material but the fact that fly ash is grey-black in colour, limits the application of fly ash only to product where colour is not important. As such, a method was needed to be developed to increase the whiteness of fly ash without reducing the advantages of it as a cheap material. In this research, twelve commercially provided fly ash samples from Australian thermal power stations were investigated with respect to composition. Seven of them were thermally modified and further investigated and characterized with respect to colour, size, size distribution, and density. Of these seven fly ashes a particular grade was modified to a whiteness of 93.3 in L*a*b* scale (using barium sulfate as standard), without changing other inherent properties such as particle size and density. By comparison L*a*b* value for Omy carb 20, based on calcium carbonate is 96.9. The whiteness of fly ash was increased using a one stage thermal method ensuring the related cost of production would be not a major hurdle. The next aspect of the thesis involved incorporating as-received and heat treated fly ash samples in isotactic polypropylene up to 80 parts of fly ash per hundred resins (phr), demonstrating that fly ash content in polypropylene composites can be quite high with properly maintained combination of mechanical properties -- in particular up to 200 % improvement in Young's modulus and 63 % gain in notched impact properties, as explained in the thesis. Whilst the Young's modulus properties of the fly ash PP composites match very well with Kerner model, they lie in between the Rule of Mixture series and parallel. The tensile strength properties obtained in this research are at least 25 % higher than those predicted by Nielsen, Landon and Nicolais; whereas the strain to failure values are between 25 - 50 % higher than those predicted by Nielsen, and Smith. Whilst tensile strength of the fly ash filled polypropylene composites were less than the original polypropylene samples, as normally reported in the literature, in this thesis surface modification of fly ash particles by using 10% vinyl triethoxy silane (VTES) coupling agent gave a nominal increase in tensile strength especially at higher fly ash content. The final aspect involved study of oxidation behavior of fly ash filled polypropylene composites. Fillers, including fly ash can shorten the life time of polymers from both chemical as well as physical factors. As-received fly ash contains iron based impurities which may catalyze the anti oxidant in polypropylene, therefore reducing the service life time of the polymer. In this work, thermal treatment studies showed that the iron in fly ash can be changed to a chemically inert material so the effective service life of the polymer will only be influenced by physical factors. Therefore thermal treatment of fly ash not only increases the whiteness but also it reduces the risk of the filler on the life time of the polymer, and hence the composites.

Bibliography: leaves 213-223. / xv, 223 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis examines the cell-fluid interactions that occur during homogenization and combines them with an investigation of the mechanical properties of the cell. This results in a predictive model for cell-disruption efficiency during high-pressure homogenization. The mechanical properties of individual cells are characterised using a micro-manipulation technique. / Thesis (Ph.D.)--University of Adelaide, Dept. of Chemical Engineering, 1997

Licentiatavhandling (sammanfattning) Alnarp : Sveriges lantbruksuniversitet. / Härtill 3 uppsatser.

Thesis (Ph. D.)--Materials Science and Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Thadhani, Naresh; Committee Member: Doyoyo, Mulalo; Committee Member: Kecskes, Laszlo; Committee Member: Li, Mo; Committee Member: Sanders, Thomas; Committee Member: Zhou, Min.

Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv., 2008. / Härtill 5 uppsatser.