PS-based nonionic, but polar, diblock copolymers (polystyrene-b-polymethacrylates, polystyrene-b-polyacrylates, polystyrene-b-poly(dimethyl siloxane)) have been systematically studied using the Langmuir film balance (LFB) technique, transmission electron microscopy (TEM), and atomic force microscopy (AFM). It has been found that these nonionic copolymers can form 2D surface micelles as has been found for ionic diblocks such as polystyrene-b-poly(vinyl pyridinium iodide) diblocks. This suggests that formation of surface micelles is a general phenomenon among AB diblock copolymers. Both structural parameters (aggregation number, aggregate size distribution, corona length and thickness, morphologies, boundaries etc.) and the response to conditions (temperature of the subphase, surface tension of the subphase, hysteresis, compression rates, etc.) have been explored for the monolayers formed from these materials. Many of these diblocks exhibit plateaus or inflections in their isotherms. Experimental data allow for the calculation of the thermodynamic parameters $ rm ( Delta S sb{t}$ and $ rm Delta H sb{t})$ associated with the transitions. Differences between the $ rm Delta S sb{t}$ and $ rm Delta H sb{t}$ values observed with the nonionic diblocks in question and the ionic diblocks studied before suggests that the nonionic diblocks monolayers have unique properties. Different mechanisms of the transitions(s) are proposed for samples which have one transition plateau or inflection and samples which have multiple transitions or inflections. A scaling theory-based calculation of the corona length and $ pi$-A isotherm are reasonably consistent with experimental data and thus provides a useful tool in these studies. Selected properties (i.e. subphase surface tension, waiting time etc.) for several ionic diblocks were also studied. Finally, the minimum chain lengths for circular micelles were calculated using a scaling theory methodology.

A new method of incipient melting temperature (IMT) detection, continuous heating and fracture (CHF) method, has been developed in which a constant strain rate tensile or torsion deformation is applied to a specimen whose temperature is simultaneously increased. The IMT is determined in a single test and any phase transformations before the IMT will also be detected by the effects on the stress vs. strain behavior in the same experiment. This method also provides information about the effect of phase transformation and temperature on the mechanical behaviour of steel near the incipient melting temperature. / By means of such tests, the incipient melting behaviour of a series of steels with carbon levels from 0.031 to 0.45 wt% was examined. For the steels containing 0.08-0.097%C and about 1.5%Mn, it was found that incipient melting occurs in the two phase ($ gamma$+$ delta$) region in the temperature range from 1470-1480$ sp circ$C, and is significantly influenced by microalloying elements. In the ultra-low carbon steel (0.031%C), the IMT is in the single phase $ delta$ region at 1495 $ sp circ$C, and for the medium carbon steels containing 0.3-0.42%C (hyper-peritectic) it is in the $ gamma$ single phase in the temperature range of 1401-1414$ sp circ$C. Comparison between the IMT obtained from CHF testing and the solidus temperature calculated from K-O model showed that these two values are extremely close. Since there is no nucleation barrier for melting, it seems that the CHF testing can delineate the solidus temperature in steel. (Abstract shortened by UMI.)

The effect of Si addition on the interaction between recrystallization and precipitation during multipass deformation has been investigated in terms of the no-recrystallization temperature (Tnr), the minimum temperature at which recrystallization can be completed. The Tnr was measured in three Nb microalloyed steels with Si concentrations ranging from 0.01 to 0.48wt.%. Continuous cooling conditions were employed, with interpass times of 20--200s and strains of 0.2 and 0.35 applied at a strain rate of 2s -1. / It was observed that for similar Nb contents, the Tnr increased with Si level, but appeared to saturate at long interpass times. In addition, high strains also reduced the influence of Si on the Tnr. This behaviour can be attributed to the acceleration of the Nb(C,N) precipitation kinetics by the addition of Si. With increasing interpass time or strain, the precipitates start to coarsen and, in consequence, the pinning effect due to precipitation is reduced. Therefore, under these conditions, the effectiveness of Si addition in raising the Tnr is diminished.

The superior mechanical properties of carbon nanotubes would make them excellent candidates for the next generation of composite materials. Researchers have tried to demonstrate the potential of that novel material with various degree of success. In order to complement the experimental efforts in this new field, the modeling of these new material systems is required. One challenge when modeling nanotube composites is the large scale span between the nanotube itself and the final component. The present study focuses on the creation of a framework and methodology to span three orders of magnitude in scale with interconnected models that relate performance of single-walled carbon nanotubes (SWNT) at the nanometer scale to a nano-array, nano-wire and micro-fiber with self-similar geometries. The geometry chosen is the helical array composed of discontinuous SWNT. The five elastic constants of the twisted SWNT fibers are then predicted using a finite element analysis combined with the strain energy method. It is shown that the Young's modulus of carbon nanotube fiber decreases dramatically even for small twist angles (less than 20°) without any contribution to the transverse properties. Moreover, it was shown that adding the polymer and its properties can have important effects on the elastic properties of the SWNT/polymer fiber. Finally, this model is compared to the experimental data and theoretical models found in the literature.

The issue of mold cooling is one, which presents a foundry with a dilemma. On the one hand; the use of air for cooling is safe and practical, however, it is not very effective and high cost. On the other hand, water-cooling can be very effective but it raises serious concerns about safety, especially with a metal such as magnesium. An alternative option that is being developed at McGill University uses heat pipe technology to carry out the cooling. / The experimental program consisted of designing a permanent mold to produce AZ91E magnesium alloy and A356 aluminum alloy castings with shrinkage defects. Heat pipes were then used to reduce these defects. The heat pipes used in this work are novel and are patent pending. They are referred to as McGill Heat Pipes. / Computer modeling was used extensively in designing the mold and the heat pipes. Final designs for the mold and the heat pipes were chosen based on the modeling results. / Laboratory tests of the heat pipe were performed before conducting the actual experimental plan. The laboratory testing results verified the excellent performance of the heat pipes as anticipated by the model. / An industrial mold made of H13 tool steel was constructed to cast nonferrous alloys. The heat pipes were installed and initial testing and actual industrial trials were conducted. This is the first time where a McGill heat pipe was used in an industrial permanent mold casting process for nonferrous alloys. / The effects of cooling using heat pipes on AZ91E and A356 were evaluated using computer modeling and experimental trials. Microstructural analyses were conducted to measure the secondary dendrite arm spacing, SDAS, and the grain size to evaluate the cooling effects on the castings. The modeling and the experimental results agreed quite well. The metallurgical differences between AZ91E and A356 were investigated using modeling and experimental results. Selected results from modeling, laboratory and industrial trials are presented. The results show a promising future for heat pipe technology in cooling permanent molds for the casting of nonferrous alloys.

<p> This thesis consists of two topics: Thermal strain of concrete under low temperatures, and durability and processing techniques of concrete with CNTs. The low temperature test studies the anti-freezing action of concrete under cooling environment. Concrete mixes using different amounts of air-entraining agent and water/cement ratios were made and cured under different humidity environments. During the cooling process from 10 &ordm;C to -25 &ordm;C, the strain of concrete was measured every 3~5 &ordm;C. The strain-temperature curve of concrete under different mixing proportion was produced from these results. A numerical model was developed based on the theory of the self-consistent model. No knowledge of real pore shapes is needed to apply in the model. The only inputs for the model came from the (Brunauer-Emmett-Teller) BET test, which gave the pore size distribution of concrete sample. The validity of the numerical model was compared to the experimental results, and showed similarity in trend and peak strain. CNT is one of the most popular topics in engineering. CNT has an extremely high strength and Young's modulus. CNT is a nano-scale material, however, and tends to clump together, which makes it difficult to apply. Other research has successfully incorporated CNT into cement paste and polymer materials. This has not yet been done into concrete. This research mainly focuses on the important factors that must be solved to adopt CNT in concrete area. An ultrasonicator was used to aid the dispersion and distribution of CNT in water, while several chemicals were also adopted for this purpose. Both strength and durability were tested for CNT concrete of different mix designs. It is suggested that ultrasonicator can improve the strength of pure CNT concrete (without chemicals) by around 100%. In addition, the sodium polyacrylate treated CNT concrete has showed best durability result and good strength result. </p>

<p> The effects of vapor-grown carbon nanofiber (VGCNF) weight fraction, applied stress, and temperature on the viscoelastic responses (creep strain, creep rate, and creep compliance) of VGCNF/vinyl ester (VE) nanocomposites were studied using a central composite design (CCD). The nanocomposite test articles were fabricated by high shear mixing, casting, curing, and post-curing in an open face mold under a nitrogen environment. Short-term creep/creep recovery experiments were conducted at prescribed combinations of temperatures (23.8 - 69.2 C), applied stresses (30.2 - 49.8 MPa), and VGCNF weight fractions (0.00 - 1.00 parts of VGCNF per hundred parts of resin, phr) determined from the CCD. The response surface models (RSMs) for predicting these viscoelastic responses were developed using the least squares method and an analysis of variance procedure. The response surface estimates indicate that increasing the VGCNF weight fraction marginally increases the creep resistance of the VGCNF/VE nanocomposite at low temperatures (i.e., 23.8 - 46.5 C). However, increasing the VGCNF weight fraction for temperatures greater than 50 C decreased the creep resistance of these nanocomposites. The latter response may be due to a decrease in the nanofiber-to-matrix adhesion as the temperature is increased. The RSMs for creep strain, creep rate, and creep compliance revealed the interactions between the VGCNF weight fraction, stress, and temperature on the creep behavior of thermoset polymer</p>

<p> A series of mechanical tests was performed on a matrix of pressure vessel alloys to establish correlations between shear punch tests (SPT), microhardness (Hv), and tensile data. The purpose is to estimate tensile properties from SPT and Hv data. Small specimen testing is central to characterization of irradiation-induced changes in alloys used for nuclear applications. SPT have the potential for estimating tensile yield and ultimate strengths, strain hardening and ductility data, by using TEM disks, for example. Additional insight into SPT was gained by performing finite element analysis (FEA) simulations. </p>

<p> The penetration of granular materials is of interest to a variety of different fields, and is an active area of research. The objective of this project is to gain understanding of the dynamics of a projectile penetrating into a granular material. To do this, experiments were run and a numerical model was created. </p><p> A dart gun was used to accelerate an aluminum dart to velocities around 100 m/s, which then impacted a target tank filled with Ottawa sand. The dart flew along a view window, which allowed for a recording of the penetration event using a high speed camera. Pressure gauges inserted into the target tank measured the timing and magnitude of the compaction wave created by the dart. In these penetration events a two wave structure was discovered; a compaction wave and a fracture wave. The fracture wave is characterized by a white cone around the nose of the dart, which is created by increased reflectance from the newly created fracture surfaces in the grains of sand. </p><p> An experiment was conducted in which single grain of sand was crushed. From this experiment it was discovered that the phenomenon that creates increased reflectivity is the creation of fractures faces in the sand, and is not triboluminescence. Stress-strain data for the sand was also gathered, to be used in the numerical simulation. An ultrasonic pulser/receiver was used to gather data on the longitudinal and shear wave sound speeds through "as poured" Ottawa sand; 263 m/s and 209 m/s respectively. It was determined that the compaction and damage wave speeds were not related to either the longitudinal or shear wave speeds. </p><p> A numerical model was created using an EMU Peridynamic code. This code utilizes integral rather than differential equations, which allows for the modeling of crack propagation and fracture. The numerical simulations run were two-dimensional and on a smaller scale than the penetration experiments. The numerical simulation showed evidence of a compaction wave, force chain creation, and grain fracture, all of which were also observed in the penetration experiments.</p>

<p> Grain boundary embrittlement in the Cu-Bi alloy system was investigated using small-scale fracture toughness tests that were based on commonly used bulk-scale tests. Tests were conducted on pure and Bi-doped &lt;001> twist Cu bicrystals with misorientation angles of 6, 13, and 33&deg; in order to determine the effect of misorientation angle on the degree of embrittlement. The results of these tests showed that the 6&deg; grain boundary was nearly immune to embrittlement, showing little to no differences in fracture toughness values and failure mechanisms between the pure and doped specimens. However, the 33&deg; boundary exhibited a significant amount of embrittlement, with a nearly 40% decrease in fracture toughness in the doped specimens compared to the pure and a distinct shift in the failure mechanism from transgranular shear to intergranular fracture. The 13&deg; boundary exhibited an intermediate amount of embrittlement with a measurable drop in toughness, but not a clear shift in the failure mechanism. These results are consistent with previously published results from tests on bulk-scale bicrystals.</p><p> Furthermore, a single-crystal plasticity model was incorporated into a commercial finite element software package (ABAQUS) in order to investigate the development of the plastic zone in front of the notches created in the test specimen. It was found that the size of this zone was likely constrained by the specimen dimensions, which had a significant impact on the measured fracture toughness values.</p>