Thèse doctorat : Génie des Matériaux : Villeurbanne, INSA : 2005. / Titre provenant de l'écran-titre. Bibliogr. p. [119]-127.

Thèse doctorat : Génie des Matériaux : Villeurbanne, INSA : 2001. / Titre provenant de l'écran-titre. Bibliogr. p. 313-320.

Reproduction de : Thèse de doctorat : Génie mécanique : Toulouse, INPT : 2007. Reproduction de : Thèse de doctorat : Génie mécanique : Boumerdes (Algérie), Université M'hamed Bouguera : 2007. / Thèse soutenue en co-tutelle. Titre provenant de l'écran-titre. Bibliogr. 63 réf.

Thèse de doctorat : mécanique et matériaux : Ecole centrale de Paris : 2009. / Titre provenant de l'écran-titre. Bibliogr. 161 réf.

Thesis (M.S.)--Brigham Young University. Dept. of Mechanical Engineering, 2003. / Includes bibliographical references (p. 53-56).

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

I investigate the trading decisions of a large institutional liquidity trader by using a detailed data set from a transition management firm. The data set contains records for all trades of transitions completed between January 2008 and September 2008. Effective execution involves a trade off between trading patiently over time to minimize price impact costs and trading quickly to avoid opportunity costs due to price volatility. I estimate a model of transition duration that accounts for volatility, an order's percentage of average daily volume, and the bid--ask spread to uncover the firm's strategy of how quicklyto trade. To understand the firm's intermediate trading decisions, I estimate a vector autoregression that summarizes the dynamic relationship of volatility, trading volume, the bid--ask spread, and order type and order duration. My analysis suggests that the firm behaves strategically to minimize the total costs of trading.

Transformation Induced Plasticity (TRIP) steels have both high strength and high ductility. Retained austenite in the microstructure, upon straining, transforms to martensite and this absorbs energy and improves the work hardening of the steel, giving improved elongation. The transformation can be either stress-assisted or strain-induced and the initiation and the mechanism depend on the composition of, the size and shape of, and the phases surrounding, the austenite grains. It is important to understand the relationship between these variables and the properties of the TRIP steel. The aim of this work was to determine how the microstructure of the TRIP steel affects the transformation. Four experimental microstructures were developed, containing austenite grains with different sizes, shapes, and surrounding phases. The Fine microstructure had thin elongated austenite laths between fine bainitic ferrite laths, the Coarse microstructure had elongated austenite grains between coarser bainitic ferrite laths, the Equiaxed microstructure had equiaxed austenite grains in a matrix of equiaxed ferrite and the Acicular microstructure had elongated austenite grains surrounded by recovered ferrite laths. Tensile tests were performed and detailed characterization, using neutron diffraction, was done of samples with the four microstructures. The variation in the amount of austenite during deformation was measured. The tensile tests revealed that the microstructures had different mechanical properties and different transformation behaviours. Fine had the lowest elongation and the highest strength. Acicular and Equiaxed had good elongation but lower strength. Coarse had intermediate strength and Equiaxed had sustained work hardening. The transformation in Fine and Coarse was minimal. Coarse had some slow, steady transformation, but Fine may have had none. The transformation in Equiaxed was larger. It started quickly and then slowed at higher strains. The austenite in Acicular transformed steadily. The predominant mechanism of transformation was stress-assisted transformation, with strain-induced transformation occurring only in Equiaxed. The results of this work showed that the influence of the surrounding phases on the stability of the austenite is significant. The differences in the transformation behaviour of the four microstructures seemed to be due more to the surrounding phases than the grain size or the composition, although both these factors also played a role. / Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2007-12-14 13:35:07.248

This study examines the static recovery behaviour of a clad aluminum alloy manufactured by Novelis FusionTM technology after 72% cold rolling. The clad alloy system studied consisted of a core AA6XXX alloy clad on one side with AA3003. The Recovery at the inter-alloy region is compared with the recovery of core AA6XXX at the same depth from the rolling surface. Sample coupons from the inter-alloy region and core AA6XXX were heated isochronally and isothermally, at different temperatures and times, respectively, to probe the recovery kinetics of the X-ray peak broadening, X-ray macro-texture and micro-hardness from the cold rolled state. The recovery of the {220} and {311} X-ray line profiles were observed between the anneals. A pseudo-Voigt fit function was fit to the profile to obtain the defect related information. Recovery in the peak broadening began by 100°C and correlated to a decrease in the hardness. Sharpening of X-ray profiles during recovery is attributed to the microstructural evolution resulting from preferred release of the stored energy due to dislocation rearrangement and annihilation. Kinetic behaviour of the recovery is measured by observing the evolution of X-ray profiles and hardness during isothermal annealing at two different temperatures. Recovery behaviour in the inter-alloy region is measured to be relatively slower than the recovery of the core AA6XXX after same macroscopic pre-strain. Activation energy for recovery is calculated from the isothermal data to deduce a recovery mechanism. The activation energy calculated in core AA6XXX, 1.7eV, is close to the activation energy value for diffusion of Mg in Al (1.3-1.7eV). This indicates a possible role of Mg diffusion in the recovery of AA6XXX. The relatively higher activation energy for recovery of 2.9eV measured in the inter-alloy region may be due to pinning by nano-scale Al-Mn precipitates. The X-ray broadening data is deconvoluted to determine the apparent dislocation content using a modified Williamson-Hall model. The dislocation density measured in the AA6XXX and inter-alloy regions in the deformed and recovered conditions indicates that dislocation density is a suitable parameter that represents the stored energy that drives subsequent structural evolution during recovery. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2011-09-30 19:02:44.02