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Made available in DSpace on 2014-10-09T12:29:29Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:52Z (GMT). No. of bitstreams: 1 00980.pdf: 2060410 bytes, checksum: 24b105c62d3d7d70b79bc6c4a7f00d2a (MD5) / Tese (Doutoramento) / IEA/T / University of Washington - Wash

This investigation involved creep and moisture movement measurements for about six months on 13-course clay (Engineering class B) and calcium silicate brickwork, and 5-course concrete blockwork, consecutively. Four different geometries of masonry were built, namely: single-leaf wall, cavity wall, hollow pier and solid pier, respectively having volume/surface area (V/S) ratios of 44,51,78 and 112 mm. Deformations were also measured on one-brick wide 5 or 6-stack high model brickwalls which were partly sealed to simulate the V/S ratios of the corresponding 13-course brickwork. At the same time, deformations were also measured on individual mortar prisms and brick or block units in order to verify composite model expressions for predicting masonry movements. Simulation of moisture diffusion of the corresponding mortarjoints and embedded bricks or block were made in terms of V/S ratio by partial sealing of the individual mortar prisms and brick or block units. The tests reveal that the modulus of elasticity to be independent of masonry geometry. However, there is a clear influence of geometry on the vertical ultimate creep and moisture movement of all the masonry types i,.e. creep and shrinkage increase with a decrease of V/S ratio. A similar trend occurs for horizontal shrinkage except for the clay brickwork which undergoes moisture expansion. Deformations of the model walls show reasonable agreement with the 13-course brickwork. When results of individual mortar and brick/block specimens are inserted in composite models,the predicted strains show good agreement with the measured strains, particularly in the vertical direction. There is no consistent pattern in the distribution of load and moisture strains for the different masonry geometries, and the measurements reveal that actual strains can be up to 100% higher than the average strains.

No description available.

Creep degradation of steam carrying vessels in the power generation industry is a concern that needs to be constantly monitored. The Weldcore® process has been earmarked as a potential method of creep sampling which will allow for thick-walled sections to be analysed. A component of the process involves plugging the resultant hole after removing a creep sample using a novel welding technique called friction hydro pillar processing. At the commencement of this study, insufficient data was available to warrant safe industrial application of the process. This research was conducted to evaluate the performance of 10CrMo910 friction hydro pillar process welds. The effects of downward force, stud taper angle, hole taper angle and hole base diameter on process response, defect population, static properties and dynamic performance were evaluated. The variation of downward force showed that higher forces produce significantly smaller defects and higher fatigue life. The occurrence of defects was linked to process parameters and geometry thereby identifying the correct parameters for safe use in the power generation industry. Flash formation was identified as an early indicator of weld defects and can assist with quality control in industrial applications. Methods of standardising the plunge depth and forge force were developed to identify the correct magnitudes for different geometries, without the need for testing. Defects were shown to populate specific regions of the weld and produce variations in fatigue life. Crack initiation sites were detected which will aid in identifying areas of focus in further research and development. Temperature measurements were linked to the occurrence of defects and crack initiation sites and have been identified as a method of identifying defective welds. The effects of process parameters and stud and hole taper angles on energy inputs and near interface temperatures were statistically evaluated. Downward force was shown to have the largest effect on energy input rates, total energy input and temperatures at the 11.5mm and 20.5mm positions. Smaller hole and stud taper angles produced lower energy inputs and were identified as more energy efficient than the larger taper angles. A regression model was also developed to predict the fatigue life of welds and can assist with critical process related decision making. A range of hole base diameters were identified which produced welds with low defect populations and fatigue performance similar to that of the parent plate. Larger hole base diameters were shown to produce significant defects along the hole bottom fillet, in the weld nugget and along the bond line. Temperature measurements of the larger diameter welds showed a delay in response and are attributed to a delayed contact of plasticised stud material with the sidewall. Welds with hole base diameters larger than 11mm produced unrepeatable and defective welds, and also required higher energy inputs making smaller diameters more desirable. Analysis of all welds in this study revealed that clearance and interfacial pressures characterise the quality of friction hydro pillar process welds, therefore models were developed to aid in critical decision making with respect to downward force and geometry. This study has successfully evaluated the effects of process parameters and geometry on the properties of friction hydro pillar process welds and thereby has increased understanding of the process.

No description available.

No description available.

A Zn - 1 wt % Al alloy has been studied in an attempt to relate tensile data and metallographic observations to assumed modes of superplastic deformation. Tensile testing, was carried out at a constant crosshead speed to determine the stress versus strain rate relationships as a function of grain size and temperature. Further analysis included activation energy determinations, low temperature (-100°C) deformation behavior, deformation grain growth characteristics, and surface and internal metallography. Stage II deformation was consistent with a process combining boundary sliding and migration and boundary diffusion. Deformation in stage I was characterized by a low strain rate sensitivity and a variable activation energy. Normal slip processes were operative during stage III deformation. Deformation grain growth and anisotropic grain shape changes were pronounced and variable in stages I and II. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

A qualitative analysis of current creep theory has been made by studying the creep of polycrystalline lead. The behaviour of the low temperature stress-strain curve with prior creep history, and the strain response to decreases in creep stress were examined. The effect of temperature and creep strain on the low temperature stress-strain curve was investigated over the temperature range 0.5Tm to 0.8Tm. Specimens were quenched to 77°K. after creep and strained to determine the stress-strain curve. The 77°K. yield stress was found to increase during primary creep and remain constant in steady state. Increasing the creep temperature drastically lowered the low temperature yield stress. The reversible flow stress ratio was found to decrease with increasing temperature. These observations were in qualitative agreement with both a reaction rate theory and a rearrangement model. Stress decrease tests were carried out by reducing the creep stress after deforming the specimen varying amounts into primary and steady state in the temperature range 0.5Tm to 0.85Tm . The strain response to a stress decrease in steady state was in best agreement with the simple recovery theory. The variation In yield stress due to non-regular obstacle spacing was found to be extremely small at all temperatures and did not behave in accordance with the qualitative predictions of the rearrangement theory. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

The stress/strain relationship for most engineering materials is known to be time dependent. This is most evident during a creep test in which continual deformations are observed under constant stress conditions. In the laboratory, a specimen of cohesive soil subjected to a constant shear stress may fail after having deformed alt relatively slow rates for a considerable time. This type of failure, termed creep rupture, is also known to occur in the field. Results of drained and undrained triaxial creep rupture tests are presented in this thesis. These tests were performed on a sensitive marine clay from western Canada which was consolidated to various stress histories. Pore pressure measurements were taken during undrained tests using an electrical transducer. In addition to the creep rupture tests, incremental load and constant strain rate triaxial tests were performed for comparative purposes. The strain rate during a creep rupture test was observed to initially decrease as the specimen strained, reach a transient minimum strain rate, and then increase until rupture. Failure was found to be inevitable whenever the strain rate started to increase after having reached a minimum value. Pore pressures measured during the undrained tests did not reflect the onset of creep rupture at the transient minimum strain rate, and therefore, the onset of creep rupture cannot be explained in terms of effective stresses. A relationship was found to exist between the deviator stress, strain and current strain rate during undrained triaxial tests having the same consolidation history. This relationship permitted the prediction of the results of constant strain rate tests based on the results of creep rupture tests. This resulted in an understanding of the interrelation between the transient minimum strain rate of a creep rupture test and the maximum deviator stress of a constant strain rate test. Once the transient minimum strain rate had been reached, the results of creep rupture tests showed that the strain rate was inversely proportional to the time remaining before rupture. This relationship is independent of stress level, consolidation history and drainage conditions. As a result, it is suggested that measurement of deformations in the field can be used to predict the time until a sudden failure would be anticipated. The upper yield strength, defined as the maximum compressive stress which will not cause a creep rupture failure, was evaluated from both creep rupture and constant strain rate tests. It was found that the compressive strength increased as a linear function of the cube root of the strain rate. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate