<p>In this dissertation, we first used high-speed X-ray phase contrast imaging and infrared thermal imaging techniques to study the formation processes of adiabatic shear bands in aluminum 7075-T6 and 6061-T6 alloys. A modified compression Kolsky bar setup was developed to apply the dynamic loading. A flat hat-shaped specimen design was adopted for generating the shear bands at the designated locations. Experimental results show that 7075-T6 exhibits less ductility and a narrower shear band than 6061-T6. Maximum temperatures of 720 K and 770 K were locally determined within the shear band zones for 7075-T6 and 6061-T6 respectively. This local high temperature zone and the resulting thermal instability were found to relate to the shear band formation in these aluminum alloys. Secondly, a high-speed laser phosphorescence thermal imaging technique is developed and integrated with the compression Kolsky bar setup. The temperature field measurement during dynamic loading are performed at 100 – 200 kHz frame rate with a spatial resolution of 13 µm/pixel. The dynamic compression of copper shows 312 K temperature rise among the material surface. Experiments with thermocouple are also conducted and the results verifies the laser measurement. In the dynamic shear of aluminums, the temperature evolution during adiabatic shear band formation was observed and the results are compared with infrared measurements. The shear band was found forming at approximately 400 K and 440 K for 7075-T6 and 6061-T6, respectively, while the maximum temperature is measured as 650 K for 7075-T6 and 800 K for 6061-T6. Although the maximum temperature agrees with the infrared results, thermal softening is not considered as the main cause of the ASB formation due to the low temperature when the shear band forms.</p>

Winter road maintenance activities are crucial for maintaining the accessibility and traffic safety of the road network during winters. Common winter road maintenance activities include plowing and the use of de-icing agents (e.g. NaCl) to avoid freezing. Effective winter road maintenance strives towards keeping the roads free from snow and ice while reducing negative side effects of winter road maintenance, such as ground water contamination from road salt. Since the weather is decisive for when there is an increased risk of slipperiness, the understanding and continuous observation and forecasts of the road weather are of highest importance. Sensors are commonly installed along roads to measure road weather conditions to support the road maintenance personnel in taking appropriate actions. Different types of errors and uncertainties related to sensors used for frost warnings along roads have been investigated by using a regional scale dataset from south-western Sweden. The results from this study indicate that various types of uncertainties originate from both measurements and models which have a significant impact on the winter road maintenance efficiency. To provide better information about the road surface conditions, a new method for detecting ice formation on roads is presented. Infrared sensors were used to detect temperature patterns which may occur when ice formation take place on a road surface. The investigations demonstrate the potential to improve winter road maintenance by introducing new methods to better describe the road surface conditions. / QC 20101206

Thermographic phosphors are useful compounds to determine temperature, due to their luminescence characteristics being a function of temperature. In this research, Zinc Oxide: Gallium was evaluated for its ability to measure the temperature of an impact event in a drop weight apparatus. Different solids loadings of the phosphor were placed in a sylgard binder and these samples were then excited by a 355 nm laser as they were impacted. Images of the event were captured through two separate filters with a high-speed camera, from which intensity ratios were formed. These intensity ratios correlated to a temperature, revealing the change in temperature of the sample throughout the impact. Initial testing at a repetition rate of 500 kHz provided insignificant data, due to difficulties with timing. The whole impact event was not able to be captured, and the imprecise timing of the drop did not allow for imaging of a specific area of the impact. Moving to a slower repetition rate of 50 kHz, the entire impact was captured on the high-speed camera, showing three separate areas of interest. The first section of this area was where the impact was first initiated, resulting in a temperature increase. Next, there was a temperature decrease, where the energy from the drop weight transitioned to deforming, rather than heating the sample. Lastly, there was a final temperature rise when the sample was fully compressed, but the impact was still occurring. This trend presented itself in all of the samples, supporting the idea that when combined with the intensity ratio method, ZnO:Ga embedded in a sylgard binder is an appropriate method to determine the temperature changes in a high-speed impact event.

In the near future, Gen II, III, and IV nuclear reactors will be in operation. UO2 is a common fuel for reactors in each of these generations and molten salts are used as coolant/fuel in Gen IV molten salt reactors. This thesis investigates potential ways to measure thermal conductivity for these materials: Raman thermometry for UO2 and a needle probe for molten salts. Four Raman thermometry techniques are investigated in this thesis: The Two Laser Raman (TLR), Time Differential Domain Raman (TDDR), Frequency Resolved Raman (FRR), and Frequency Domain Raman (FDR). The TLR is a steady state method used with a thin film. The TDDR and FRR are both time domain methods used with thin cantilever samples. The FDR is a frequency domain method used with a thermally thick sample. Monte Carlo like simulations are performed for each technique. In the simulations, the affect introduced uncertainty has on the measurement of thermal conductivity and thermal diffusivity is measured. From the results, it is recommended that the TLR should be used for measuring thermal conductivity and the FRR used for measuring thermal diffusivity. The TDDR and FDR were heavily affected by the uncertainty which resulted in inconsistent measured thermal properties. For measuring the thermal conductivity of molten salt, a needle probe was designed and manufactured to withstand the corrosive environment found in using molten salts. The probe uses modulated joule heating and measures the temperature rise in a thermocouple. The phase delay and temperature amplitude of the thermocouple are used in determining the thermal conductivity. A new thermal quadrupole based analytical solution, which takes into consideration convection and radiation, to the temperature rise of the probe is presented. The analytical solution is verified using a numerical solution found using COMSOL. Preliminary data was obtained with the probe in water.

This licentiate thesis presents developments of nanocalorimetry systems tailored for use under extreme conditions such as high pressure, intense magnetic fields, and low temperature. Nanocalorimetry is a powerful approach to study strongly correlated systems like superconductors, heavy fermions, and quantum materials with non-trivial magnetic or electronic properties, materials with emergent magnetic orders, as well as quasicrystals. Introducing high pressure or magnetic fields as tuning parameters in specific heat measurements at low temperatures can enhance the understanding of underlying physical properties of such materials. The key component of calorimeters is the thermometer. A thin-film thermometer based on a composite ceramic metal oxide has been developed. It shows high sensitivity and negligible magnetoresistance over a broad temperature range. Two different nanocalorimeters are fabricated starting from an existing nanocalorimeter design, a high-pressure nanocalorimeter and a calorimeter for sample rotations in high magnetic fields. The high-pressure nanocalorimetry setup involves a nanocalorimeter built on a robust substrate combined with a diamond anvil cell, a gasket sandwich with electric leads, and an optical setup for pressure detection through ruby fluorescence spectroscopy. The high-field nanocalorimeters are fabricated on SiNx membranes for specific heat measurements down to 30 mK. Miniaturization is performed to extend their use for angular-dependent measurements in high magnetic fields, so far used up to 41 T. Reducing the calorimeter platform size in both calorimeters is achieved by a method of plasma etching performed after device fabrication. Specific heat measurements of Eu-doped GdCd7.88 quasicrystals and GdCd6 approximant systems are performed in fields up to 12 T. The preliminary results show the presence of spin-glass behavior in the quasicrystals and an antiferromagnetic transition in the approximant crystals at low temperatures.

No description available.

Polymer extrusion is an energy intensive process whereby the simultaneous action of viscous shear and thermal conduction are used to convert solid polymer to a melt which can be formed into a shape. To optimise efficiency, a homogeneous melt is required with minimum consumption of process energy. In this work, in-process monitoring techniques have been used to characterise the thermal dynamics of the single screw extrusion process with real-time quantification of energy consumption. Thermocouple grid sensors were used to measure radial melt temperatures across the melt flow at the entrance to the extruder die. Moreover, an infrared sensor flush mounted at the end of the extruder barrel was used to measure non-invasive melt temperature profiles across the width of the screw channel in the metering section of the extruder screw. Both techniques were found to provide useful information concerning the thermal dynamics of the extrusion process; in particular this application of infrared thermometry could prove useful for industrial extrusion process monitoring applications. Extruder screw geometry and extrusion variables should ideally be tailored to suit the properties of individual polymers but in practise this is rarely achieved due the lack of understanding. Here, LDPE, LLDPE, three grades of HDPE, PS, PP and PET were extruded using three geometries of extruder screws at several set temperatures and screw rotation speeds. Extrusion data showed that polymer rheology had a significant effect on the thermal efficiency on the extrusion process. In particular, melt viscosity was found to have a significant effect on specific energy consumption and thermal homogeneity of the melt. Extruder screw geometry, set extrusion temperature and screw rotation speed were also found to have a direct effect on energy consumption and melt consistency. Single flighted extruder screws exhibited poorer temperature homogeneity and larger fluctuations than a barrier flighted screw with a spiral mixer. These results highlighted the importance of careful selection of processing conditions and extruder screw geometry on melt homogeneity and process efficiency. Extruder scale was found to have a significant influence on thermal characteristics due to changes in surface area of the screw, barrel and heaters which consequently affect the effectiveness of the melting process and extrusion process energy demand. In this thesis, the thermal and energy characteristics of two single screw extruders were compared to examine the effect of extruder scale and processing conditions on measured melt temperature and energy consumption. Extrusion thermal dynamics were shown to be highly dependent upon extruder scale whilst specific energy consumption compared more favourably, enabling prediction of a process window from lab to industrial scale within which energy efficiency can be optimised. Overall, this detailed experimental study has helped to improve understanding of the single screw extrusion process, in terms of thermal stability and energy consumption. It is hoped that the findings will allow those working in this field to make more informed decisions regarding set conditions, screw geometry and extruder scale, in order to improve the efficiency of the extrusion process. / Engineering and Physical Sciences Research Council

Non-intrusive acoustic thermometry using an acoustic impulse generator and two microphones is developed and integrated with tomographic techniques to reconstruct temperature contours. A low velocity plume at around 450 °F exiting through a rectangular duct (3.25 by 10 inches) was used for validation and reconstruction. 0.3 % static temperature relative error compared with thermocouple-measured data was achieved using a cross-correlation algorithm to calculate speed of sound. Tomographic reconstruction algorithms, the simplified multiplicative algebraic reconstruction technique (SMART) and least squares method (LSQR), are investigated for visualizing temperature contours of the heated plume. A rectangular arrangement of transmitter and microphones with a traversing mechanism collected two orthogonal sets of acoustic projection data. Both reconstruction techniques have successfully recreated the overall characteristic of the contour; however, for the future work, the integration of the refraction effect and implementation of additional angled projections are required to improve local temperature estimation accuracy. The root-mean-square percentage errors of reconstructing non-uniform, asymmetric temperature contours using the SMART and LSQR method are calculated as 20% and 19%, respectively. / Master of Science / Computational tomography is an approach to reconstruct the cross-sectional planar image of a 3D object. This technique is widely used in the medical field using x-rays to visualize cross-sections of internal organs. Along with x-rays, acoustic rays can also be utilized with tomographic techniques. The speed of sound travelling through a gaseous medium, such as air, is depended on the density, humidity, and temperature of the medium. Using this relationship, the temperature of the medium can be calculated with known speed of sound, density, and humidity. The speed of sound can be found using the distance and time of flight of the acoustic ray using transmitter and microphones. Since the effect of density and humidity of the medium on speed of sound is relatively insignificant, those values were assumed to be constant. In this research, the acoustic temperature measuring technique using the speed of sound relationship was applied and validated, then the technique was integrated with tomography using two projection angles. A rectangular duct (3.25 by 10 inches) with a heated air at around 450 °F exiting the duct was tested. The calculated temperature from acoustics was compared with values measured with thermocouples. After the acoustic temperature measuring technique was validated, multiple acoustic rays arranged in two orthogonal projections were setup. The speed of sound values from the acoustic rays were utilized to reconstruct the temperature distribution of the duct exit using two tomographic reconstruction methods: LSQR and SMART. Both reconstruction techniques have captured overall contour of the temperature. More projection angles and sound refractive properties will be utilized in the future to overcome the limitations of detailed reconstruction.

The thesis presents observations on the CO2 concentration and carbon isotopes in air CO2 (δ13C) to constrain the inter-annual variability of carbon inventory over the Southern Ocean between the years 2011-2013. Based on the observation, the region of CO2 venting was identified over the Southern Ocean. Further, isotopic characterization allowed inferring about the possible sources of CO2 degassing and contribution from the dissolved inorganic carbon (DIC) that exsolved to generate CO2. It is concluded that the origin CO2 is mainly from the degassing of CO2 available from the dissociation of DIC or organic degradation. Live Foraminiferal samples of Globigerina bulloides from towing were captured, separated and analysed for δ18O and δ13C from various locations across the Southern Ocean between 10°N−60°S. A large similarities in the estimated values (deduced from simultaneous composition of ocean water 18O, δ13C in DIC and temperature i.e. SST under equilibrium condition) and measured δ18O and δ13C values were observed until 40°S from the equator, and hence it was concluded that the calcification depth of G. bulloides is confined to a depth of ~75-200m till 40°S latitude. However, further south (>40oS) disequilibrium from the estimates was detected. A number of possible reasons were cited for the observed disequilibrium such as (1) Deeper depth habitat (2) Partial dissolution (3) Non-equilibrium calcification (4) Oceanic Suess Effect and (5) Genetic Variability. A box model of isotopic mass balance was presented in this study to explain the pattern of enrichment in the 13C values of sea water DIC with latitude (up to about 43°S). The model shows that a steady state of the carbon isotope ratio of water is achieved in a relatively short time of ~5000 days. Rainwater isotope in the open marine condition across the latitudinal transects over Southern Ocean marking zone of precipitation and evaporation is another element of this thesis. A variation with excess lighter isotopes in rainwater was observed in high latitude rain in this study. Observed isotopic depletion is attributed to rainout process over the ocean. The average rainout fraction over the Southern Ocean in the region of zone of precipitation is ~44%, while it drops to ~25% in the zone of evaporation. Second part of the thesis presents a novel method of isotope thermometry which is called “clumped isotope (13C18O16O16O-2 in the calcite structure) thermometry”. A revision in the thermometry equation relating 47 vs T in synthetic carbonates precipitates and otoliths was proposed. The revised calibration was used on fish otoliths from the modern and past environment to estimate the temperatures. Together with the clumped isotope, conventional stable isotopes in the shell carbonates were measured to effectively reconstruct the seasonal fresh water fraction at seasonal time scales.

No description available.