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Development of the simplified method to evaluate dynamic mechanical analysis data on asphalt-aggregate mixturesAb-Wahab, Yunus Bin 16 February 1993 (has links)
Testing of asphalt binders and asphalt-aggregate mixtures using dynamic
mechanical analysis is becoming popular with improvements in high-speed
computers, precision equipment, and computer software. Researchers are trying
to describe the behavior of asphalt binders and asphalt-aggregate mixtures in
terms of their time- and temperature-dependent linear viscoelastic behavior.
The objectives of this thesis were to develop a simplified pneumatic test to
perform dynamic mechanical analysis (DMA), to evaluate the performance of the
pneumatic and hydraulic test systems using the computer software developed to
perform DMA tests, and, to develop a simplified method to evaluate the
experimental data obtained from DMA tests on aged asphalt-aggregate mixtures.
A simplified pneumatic test system was developed to perform DMA.
Computer software was also developed to perform DMA testing on both the
simplified pneumatic and hydraulic test systems. DMA was performed on both
test systems to compare their performance, and on aged asphalt-aggregate
mixtures to evaluate the application of the simplified method.
The results from the pneumatic and hydraulic test systems show that there
is about a 20 percent difference in the complex modulus, especially at high loading
frequencies. This is due to the compressibility of the air used in the pneumatic
test system. The compressibility of air is greater at warmer temperatures than at
cooler temperatures. Therefore, the application of the pneumatic test system to
perform dynamic testing should be limited to low frequencies ( < 2 Hz), low
temperatures ( < 25°C), and low load ( < 454 kg (1000 lbs.)) applications unless
a modification can be made to increase the pneumatic cylinder's response time to
match the hydraulic cylinder's response time.
The simplified analysis method developed in this thesis divides the DMA
results into four complex modulus and five phase angle parameters. These
parameters describe the shapes of the master stiffness and phase angle curves and
distinguished between the different asphalt-aggregate mixtures and the aging
methods performed on the aged asphalt-aggregate mixtures. The phase angle
parameters were reduced into two variables, peak frequency and peak angle,
which vary with the aging of each asphalt-aggregate mixture. The peak frequency
and peak angle decrease as the aging severity increases and the change of peak
frequency and peak angle vary with the asphalt-aggregate mixture and aging
treatment. Therefore, the complex modulus parameters and peak frequency and
peak angle may be good indicators to describe how a master curve's shape varies
with asphalt, aggregate, and aging type. / Graduation date: 1993
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Optimisation and improvement of the design of scarf repairs to aircraftHarman, Alex Bruce, Mechanical & Manufacturing Engineering, Faculty of Engineering, UNSW January 2006 (has links)
Flush repairs to military aircraft are expected to become more prevalent as more thick skin composites are used, particularly on the surface of the fuselage, wings and other external surfaces. The use of these repairs, whilst difficult to manufacture provide an aerodynamic, ???stealthy??? finish that is also more structurally efficient than overlap repairs. This research was undertaken to improve the design methodology of scarf repairs with reduced material removal and to investigate the damage tolerance of scarf repair to low velocity impact damage. Scarf repairs involve shallow bevel angles to ensure the shear stress in the adhesive does not exceed allowable strength. This is important when repairing structures that need to withstand hot and humid conditions, when the adhesive properties degrade. Therefore, considerable amounts of parent material must be machined away prior to repair. The tips of the repair patch and the parent laminate are very sharp, thus a scarf repair is susceptible to accidental damage. The original contributions include: ??? Developed analytic means of predicting the stresses within optimised scarf joints with dissimilar materials. New equations were developed and solved using numerical algorithms. ??? Verified using finite element modelling that a scarfed insert with dissimilar modulus subjected to uniaxial loading attracted the same amount of load as an insert without a scarf. As such, the simple analytic formula used to predict load attraction/diversion through a plate with an insert may be used to predict the load attraction/diversion into a scarf repair that contains a dissimilar adherend patch. ??? Developed a more efficient flush joint with a doubler insert placed near the mid line of the parent structure material. This joint configuration has a lower load eccentricity than external doubler joint. ??? Investigated the damage tolerance of scarf joints, with and without the external doubler. The results showed that scarf joints without external doublers exhibited a considerable strength reduction following low velocity impact. Based on the observations, the major damage mechanics in the scarf joint region following impact have been identified. These results demonstrated that it is important to incorporate damage tolerance in the design of scarf repairs.
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Matric suction response of unbound granular base materials subject to cyclic loadingCraciun, Ovidiu, Engineering & Information Technology, Australian Defence Force Academy, UNSW January 2009 (has links)
The emergence of analytically-based pavement design has encouraged investigations toward a better understanding of the behaviour of pavement layers under cyclic loading. Unbound granular base (UGB) materials are commonly placed as base course layers in the design of pavement foundations. Due to their nature and geometry they are unsaturated geo-materials and therefore, it is desirable to study their behaviour using the framework of unsaturated soil mechanics. Current literature reflects very limited achievements in this direction. This thesis presents the development of a cyclic triaxial testing system and associated testing methodology that meets the challenges of testing an UGB material as an unsaturated soil. The testing system enables the initialisation of a specimen to target matric suction and facilitates direct measurement of its evolution under cyclic loading. In conjunction with the use of accurate on-specimens strain measurement transducers, ???clean??? strain and matric suction cyclic responses are obtained. Two types of cyclic triaxial testing are investigated: with constant cell pressure (i.e., CSeries testing) and with varying (cyclic) cell pressure where both axial and radial stress components are simultaneously (and in phase) pulsed (i.e., V-Series testing). Different initial matric suctions, si will be imposed in the testing program and the influence of si on material behaviour is analysed. This is investigated in a similar manner for C- and V-Series testing. The influence of si appears to be significant for both cyclic and permanent strain responses. A strong stress path dependency is found to characterise the behaviour of the UGB material. Under a wide range of cyclic deviator stress magnitudes, permanent strain response is found to correlate with that of matric suction response. Both appear to indicate better the relative performance of a UGB material than the response of resilient modulus. Another particular aspect investigated is the influence of additional fines on the behaviour of the UGB material. To ???isolate??? the effects of additional fines the cyclic and permanent strain responses of ???equivalent??? specimens with equivalent compaction and unsaturation condition, but different fines content, are compared. The results showed that the relative performance of the two materials (distinguished by the different percentage of fines content) in intertwined with the strong stress path dependency. It is also found that a material compacted at higher dry density may not improve its behaviour under cyclic loading, but may worsen with load cycles. Soil-water characteristic curve tests are conducted for the UGB materials investigated, showing high sensitivity of initial matric suction to moisture content, which increases further for the material with additional fines. This explains the notion of ???sensitivity??? of UGB materials as commonly suggested by practicing pavement engineers.
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Nitric Acid Dehydration Using Perfluoro Carboxylate and Mixed Sulfonate/Carboxylate MembranesR.L. Ames January 2004 (has links)
Thesis (Ph.D.); Submitted to Department of Chemical Engineering, Colorado School of Mines, Golden, CO (US); 1 Sep 2004. / Published through the Information Bridge: DOE Scientific and Technical Information. "LA-14178-T" R.L. Ames. 09/01/2004. Report is also available in paper and microfiche from NTIS.
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Endodontic sealers their properties and effects on fiber post retention /Najib, Farrah Huthail. January 2008 (has links) (PDF)
Thesis (M.S.)--University of Alabama at Birmingham, 2008. / Title from first page of PDF file (viewed Feb. 16, 2009). Includes bibliographical references (p. 49-57).
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The complete denture an i̲n̲ v̲i̲v̲o̲ model to evaluate wear resistance : a thesis submitted in partial fulfillment ... denture prosthodontics /Swarts, Robert G. January 1982 (has links)
Thesis (M.S.)--University of Michigan, 1982.
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The complete denture an i̲n̲ v̲i̲v̲o̲ model to evaluate wear resistance : a thesis submitted in partial fulfillment ... denture prosthodontics /Swarts, Robert G. January 1982 (has links)
Thesis (M.S.)--University of Michigan, 1982.
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Molecular assessment of biocompatibility development of an in vitro test for detection of pro-inflammatory properties of dental materials utilizing intercellular adhesion molecule-1 /Julian, Leigh Ann, Yourtee, David M. January 1998 (has links)
Thesis (Ph. D.)--School of Pharmacy and School of Dentistry. University of Missouri--Kansas City, 1998. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.
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Clinical trial to determine the accuracy of prefabricated trays for making alginate impressionsDamodara, Eswar Keran C. January 2008 (has links) (PDF)
Thesis (M.S.)--University of Alabama at Birmingham, 2008. / Title from PDF title page (viewed on Sept. 17, 2009). Includes bibliographical references (p. 46-49).
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A comparison of the effect of a restorative versus an orthodontic self-etching primer on orthodontic shear bond strengthLangley, Cranford Shane. January 2009 (has links) (PDF)
Thesis (M.S.)--University of Alabama at Birmingham, 2009. / Title from PDF title page (viewed on Sept. 3, 2009). Includes bibliographical references (p. 32-37).
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