A compressive creep study of cold compacted colloidal boehmite has been carried out during the dehydroxylation reaction. The creep tests were made as a function of temperature, applied stress and the relative density of the cold compact. The activation energy for creep has been found to be 9.1 ± 1.5 Kcal/mole. The total creep rate was due to the stress associated with the neck formation at the points of contact and the applied stress. The creep rate is proportional to the applied stress. The final form of the total creep rate equation is ė =[0.144 exp ( formula omitted )+2.2x10ˉ⁷σ] sec ˉ¹. Electron photomicrographs of fractured surfaces of deformed specimens revealed the presence of contact points in the aligned fibers, confirming the existence of the driving force for shrinkage. Equations relating the change in length and the strength of a compact with time have been tested with the experimental data, which indicated that the rate controlling mechanism may be volume diffusion for the creep process. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

A theoretical and experimental investigation into the creep of a sensitive clay under different deviator stresses is presented. The effect of deviator stress on pore-pressures within the soil is also studied. An explanation of the phenomenon of creep is offered which is based on a consideration of the micro-structure of the clay. Experimental evidence to support this explanation is presented. The experimental work consisted of standard triaxial "consolidated undrained tests" performed on cylindrical specimens. Pore-pressures were measured by means of a pore-pressure panel based on the M.I.T. design. The observed data show that, with other variables remaining constant, the strain rate increases with increase in applied stress. Experimental results do not conclusively prove the existence of an upper yield value for the clay tested, but they do suggest it as a possibility. With the temperature remaining constant, the test results show that the pore-pressure increases with increase in applied stress. Under a given applied deviator stress the pore-pressure increases at a decreasing rate and does not attain a maximum or constant value at any time during the test. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

The hypothesis is examined that short-term creep response of earlywood and latewood tissues of some coniferous species, stressed in tension parallel to the grain, is a function of microfibril angle of the S 2 layer of and relative degree of crystallinity in the tracheid cell wall, along with specific gravity of that wood tissue and its extractives content. A new technique was developed to measure the total creep that occurred over a 60-minute period of time for small specimens (nominally 0.010 in, thick) of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) (normal and compression wood), Sitka spruce (Picea sitchensis (Bong.) Carr.) and western hemlock (Tsuga heterophylla (Raf.) Sarg.), taken from earlywood and latewood zones of the same increment. Total creep was determined at two initial deformation levels, 3,000 microin.per in. (strain level No. 1) and 6,000 microin. per in. (strain level No. 2). Microfibril angle was measured by a modified mercury impregnation method, while cell wall crystallinity was determined on small, unoriented pellets by the X-ray diffraction technique. Air-dry specific gravity (oven-dry weight) and alcohol-benzene plus hot water extractives were also determined by conventional methods. Multiple regression analyses were carried out and prediction equations, based on the experimental results, have been constructed. It is shown that the variability in total creep response can best be explained by using the prediction equation which contains microfibril angle of the S2 layer, specific gravity and extractives content. The multiple coefficients of determination (R²) using this subset of variables are 0.7680 and 0.8550 for initial strain Numbers 1 and 2, respectively. Cell wall crystallinity was eliminated from the prediction equations as the least important variable due to its high inverse correlation with the microfibril angle of the S2 layer (r=0.9284). Two possible reasons are suggested to explain this correlation. First, in the case of a small angle, the scatter around the mean microfibril angle is smaller and the microfibrils probably lie almost parallel to each other. As a result, the relative degree of amorphous material required to fill the micro-spaces between microfibrils would be smaller. Considering the case of a large microfibril angle, the microfibrils are probably not parallel to each other; consequently, relatively large micro-spaces would be occupied by the amorphous material. A second possible reason for this relationship may be that cellulose chain molecules, in the case of a small microfibril angle, will have a better chance for increased frequency of cross links (bonding between neighbouring chains) along their unit length. Consequently, a tendency of improved geometric order should be observed with better chain coherence in the resulting cellulose as compared to situations associated with tracheids characterized by larger microfibril angle. It must be indicated that reasons for this high degree of correlation, as noted above, remain conjectural. Among the structural features studied, microfibril angle was shown to control creep response to the greatest extent. As it increases, total creep increases, the reason being that with a small angle, microfibrils are in a position to bear most of the applied load and therefore their relative movement towards a smaller angle would be less. This results in a small plastic deformation. In the case of a large angle, there is a possibility that the microfibrils have a large tendency to move to a smaller angle causing a large creep response. Wood samples of low specific gravity creep more than those with high specific gravity. This behavior is explained by the higher relative per cent of the S2 layer in the latter. Extractives are shown to contribute significantly to the variation in total creep. They probably act as plasticizers causing a reduction in the primary and secondary bonding between microfibrils. This would facilitate the movement of the stiff inextensible microfibrils to accommodate the creep-inducing stresses. Results obtained in this study were compatible with the proposed hypothesis. / Forestry, Faculty of / Graduate

A Sn - 1% Bi alloy has been studied to determine the effects of superplastic deformation on the grain growth kinetics. Using both constant crosshead speed and creep tests, the grain size was measured as a function of deformation time and strain over a wide range of strain rates. It was found that during deformation, considerable increases in the grain growth rates occurred when compared to static annealing. The effect was most pronounced at intermediate strain rates (≃10⁻²/minute) in the high strain rate sensitivity region. However, the grain growth rates on annealing after deformation were found to be less than static rates. To aid in understanding the mechanism of the enhanced growth, alternating tension-compression tests were performed. The amount of grain elongation and the changes in preferred orientation with deformation were also measured. Grain type and grain size distributions after deformation and after annealing were established and analyzed in terms of a grain coalescence mechanism. However, the most favourable mechanism appears to involve the production of excess vacancies in the grain boundary region leading to increased boundary mobility. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

Game developers often find themselves coming up with ideas along the production period of a game varying in size and may go unnoticed or seem insignificant to the scope of the project but in the long run add up to break deadlines, budget and affect the morale and engagement of developers. In the modern game development industry agile development methods have increased in popularity allowing flexibility in the development process. This agile approach has emerged from traditional software development where waterfall development methods are common practice (Kanode and Haddad, 2009). Through in-depth interviews with developers from Sweden, Finland, and the United Kingdom this study aims to explore how feature creep is perceived by the individual developer and its effect on the day-to-day development. The ambition is to establish whether feature creeping as a phenomenon can be a useful tool for innovation and work culture. / Spelutvecklare får kontinuerligt idéer under produktionen som varierar i storlek och kan gå obemärkta eller anses meningslösa för projektets ramar och över tid och kan påverka deadline, budget, moral och engagemang hos spelutvecklare. I dagens spelindustri har agila arbetsmetoder ökat i popularitet som möjliggör flexibla utvecklingsprocesser. De agila arbetssättet har vuxit fram ur traditionell mjukvaruutveckling där vattenfallsmetoder är ofta förekommit (Kanode och Haddad, 2009). Genom ingående intervjuer med utvecklare från Sverige, Finland och Storbritannien undersöker den här studien hur feature creep upplevs av den enskilda spelutvecklaren och dess effekt på det dagliga utvecklandet i spelbranschen med en ambition att se hur fenomenet feature creep kan vara ett användbart verktyg för innovation och arbetskulturen.

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published_or_final_version / abstract / Mechanical Engineering / Master / Master of Philosophy