A method is developed for construction of deflection curves of beam-columns stressed into plastic range by thrusts and equal end moments producing single curvature bending. Actual deflection curves are plotted for 8x8 WF 31 lb/ft section acted upon by moments and thrusts of different magnitudes. These are used for construction of the end moment vs. end slope diagrams and the interaction curves which present in graphical form the ultimate strength of beam-columns of different lengths under various combinations of thrusts and moments. The latter are compared with similar graphs contained in current specifications. The study is based on moment vs. curvature relations developed at Lehigh University. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Le titane, comme ses alliages, présente des caractéristiques remarquables qui peuvent être modulées du fait des nombreuses microstructures qu’il est possible d’obtenir. Grâce à cette grande variété, le titane et ses alliages possèdent un grand nombre de propriétés. Parmi les plus intéressantes, on peut citer leur résistance à la corrosion, leur biocompatibilité, mais aussi leurs excellentes propriétés mécaniques (résistance, ductilité, ténacité, fluage…). Pour toutes ces raisons, l’attrait pour les alliages de titane n’a cessé de croître dans de nombreux secteurs. En effet ils sont maintenant largement utilisés dans les industries aéronautique et chimique, mais aussi l’architecture, le naval, l’industrie automobile, le sport ou encore la médecine. La nanoindentation est utilisée couramment de nos jours pour déterminer les propriétés mécaniques locales des matériaux. Elle permet notamment de caractériser des alliages métalliques possédant une microstructure polycrystalline. La taille de l’indenteur en nanoindentation étant faible (de quelques micromètres à quelques dizaines de micromètres), cette technique est idéale pour caractériser les propriétés mécaniques de surface des différents grains d’un matériau. Elle permet notamment de mesurer simultanément la dureté et le module d’élasticité. Si les essais de nanoindentation sont associés à un banc motorisé X-Y, une matrice étendue d’indents peut être réalisée avec un pas de quelques micromètres. Grâce à cette technique et dans le cadre de ce travail de thèse, nous avons réalisé dans un premier temps des cartographies de dureté et de module d’élasticité (HIPF et EIPF). Dans un second temps, nous avons évalué des propriétés non-conventionnelles d’alliages de titane, telles que l’effet mémoire de forme et la superélasticité. Dans la première partie de l’étude, la nanoindentation a été corrélée à l’EBSD (diffraction des électrons rétro-diffusés) afin d’identifier la relation entre l’orientation cristallographique d’un grain et ses propriétés mécaniques. L’étude a été menée sur les alliages de composition Ti-30Nb et Ti-27Nb (%at) de structure cubique centrée (phase ), et sur le titane de pureté commerciale T40, de structure hexagonale compacte (phase ). Dans la seconde partie de l’étude, la nanoindentation a été utilisée pour mesurer l’effet mémoire de forme (SM) et la superélasticité (SE) de différents alliages de titane à travers une large gamme de profondeur d’indentation. La mesure de ces propriétés non-conventionnelles a été réalisée à partir de l’étude des courbes charge-déplacement obtenues pour chaque essai d’indentation. L’amplitude de l’effet SE et SM a été caractérisée par des ratios de hauteur et de travail déterminés par l’étude des courbes de nanoindentation ainsi que des profils AFM réalisés au microscope à force atomique. / Titanium and titanium alloys presents remarkable characteristics which can be modulated due to the many different microstructures that is possible to obtain. Thanks to this huge variety, titanium and its alloys can exhibit many properties. Among the most interesting, there may be mentioned their corrosion resistance, biocompatibility, but also their excellent mechanical properties (strength, ductility, toughness, creep…). For all these reasons, interest for of titanium alloys has been growing in many areas. Indeed they are now widely used in the aerospace and chemical industries, but also in architecture, naval, automotive, sports or medicine. Nanoindentation is commonly used nowadays to determine local mechanical properties of materials. For example, this technique allows the characterization of metallic alloys having a polycrystalline microstructure. The size of the indenter in nanoindentation being small (few microns to few tens microns), and consequently this technique is ideal for characterizing the surface mechanical properties of different grains of a material. It allows simultaneous measurement of the hardness and the elastic modulus. If nanoindentation tests are associated with a XY motorized test bed, a wide array of indents can be achieved with a step of few micrometers. Thanks to this technique and as part of this thesis, we have realized at first hardness and elastic modulus mapping (HIPF and EIPF). In a second time, we have evaluated unconventional properties of titanium alloys, such as shape memory effect and superelasticity. In the first part of the study, nanoindentation was correlated with EBSD (Electron backscattered diffraction) to identify the relationship between the crystallographic orientation of a grain and its mechanical properties. The study was conducted on the Ti-30Nb and Ti-27Nb (at.%) alloy compositions having a bodycentered cubic structure ( phase), and the commercially pure titanium (CP-Ti) having a hexagonal close packed structure ( phase). In the second part of the study, nanoindentation was used to measure the shape memory effect (SM) and the superelasticity (SE) of various titanium alloys through a range of indentation depth. The measurement of these unconventional properties was performed from the study of load-displacement curves for each indentation test. The magnitude of the SE and SM effect was characterized by depth and work ratios determined from the study of nanoindentation curves and AFM profiles.

This thesis analyzes railway demand and its determinants in the context of regional railway passenger transport in the Czech Republic and Prague suburban railway system. Special attention is devoted to examining the impact of new trains on the demand for the selected route of Jizerskohorské Railway. In particular models, I utilize as estimation procedure and difference-in-differences estimator. Panel data analysis found, in line with other published studies, short-run inelastic nature of demand. In order to increase revenue to railway operator, one must distinguish between a group of dependent and discretionary riders whose elasticity is different. Effect of buying new trains can be substantial, especially on less frequented routes with a greater proportion of private car holders.

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Within the last ten years there has been much interest in the field of elasto-plastic behavior of engineering materials. Hie recent popularity of the low-cost light-weight plastically designed structures has added a great deal of impetus to this interest. This thesis deals with one of the aspects of elasto-plastic behavior, namely, the distribution of the residual stresses in a simple member which has been plastically deformed in tension and/or compression,. In particular, an attempt has been made to relate these residual stresses to the well-known but little understood Bauschinger effect.

The behavior of anisotropic materials has been the object of much recent research® The high strength to weight ratio needed by aerospace structures has necessitated the use of exotic, composite materials which generally exhibit anisotropic behavior® These materials cannot be fully utilized unless analytical techniques are used which take maximum advantage of their anisotropic behavior.

Lightweight thermal paper (LWTP) is a noteworthy import commodity with wide usage and large import value in the United States. In this study, the trade pattern and market dynamics of the LWTP import market in the U.S. has been examined based on almost ideal demand system. The results revealed that both the trade volume and import source of LWTP had changed during last decade. Competition relationships were found among major suppliers in both the short run and long run, and the long-run competition is stronger than that in the short run. The repeal of restriction on conducting countervailing investigation against non-market economy temporarily stimulated the import of LWTP products from China, but the following antidumping/countervailing investigation and the corresponding punitive duties generated trade depression effect on the imports. In addition, positive trade diversion effect was found on German products, which raises doubt on the effectiveness of this trade remedy policy.

This work focuses on understanding deformation mechanisms and responsiveness associated with the wrinkling, folding, and snapping of thin polymer films. We demonstrated the use of elastic instabilities in confined regimes, such as the crumpling and snapping of surface attached sheets. We gained fundamental insight into a thin film's ability to localize strain. By taking advantage of geometric strain localization we were able to develop new strategies for responsive surfaces that will have a broad impact on adhesive, optical, and patterning applications. Using the rapid closure of the Venus flytrap's leafets as dictated by the onset of a snap instability as motivation, we created surfaces with patterned structures to transition through a snap instability at a prescribed stress state. This mechanism causes surface topography to change over large lateral length scales and very short timescales. Changes in the stress state can be related to triggers such as chemical swelling, light-induced architecture transitions, mechanical pressure, or voltage. The primary advantages of the snap transition are that the magnitude of change, the rate of change, and the sensitivity to change can be dictated by a balance of materials properties and geometry. The patterned structures that exhibit these dynamics are elastomeric shells that geometrically localize strain and can snap between concave and convex curvatures. We have demonstrated the control of the microlens shell geometry and that the transition time follows scaling relationships presented for the Venus flytrap. Furthermore, the microlens arrays have been demonstrated as surfaces that can alter wettability. Using a similar novel processing technique, microarrays of freestanding elastomeric plates were placed in equibiaxial compression to fabricate crumpled morphologies with strain localized regions that are difficult to attain through traditional patterning techniques. The microstructures that form can be initially described using classical plate buckling theory for circular plates under an applied compressive strain. Upon the application of increasing compressive strain, axisymmetric microstructures undergo a secondary bifurcation into highly curved, nonaxisymmetric structures. The inherent interplay between geometry and strain in these systems provides a mechanism for generating responsiveness in the structures. By swelling the elastomeric plates with a compatible solvent, we demonstrated the microstructures ability to reversibly switch between axisymmetric and nonaxisymmetric geometries. To further explore the localization of strain in materials, we have fabricated sharply folded films of glassy, homogenous polymers directly on rigid substrates. The films were uniaxially compressed and buckle after delaminating from the substrate. As the applied strain is increased, we observed strain localization at the center of the delaminated features. We found that normally brittle, polystyrene films can accommodate excessive compressive strains without fracture by undergoing these strain localizing fold events. This technique provided a unique way to examine the curvature and stability of folded features, but was not adequate for understanding the onset of folding. By taking thin films, either glassy or elastomeric, and simply lifting them from the surface of water, we observed and quantified the wrinkle-to-fold transition in an axisymmetric geometry. The films initially wrinkle as they are lifted with a wavelength that is determined by the film thickness and material properties. The wrinkle-to-fold transition is analogous to the transition observed in uniaxially compressed films, but the axisymmetric geometry caused the fold to act as a disclination that increased the radial stress in the film, thereby decreasing the wavelength of the remaining wrinkles. Further straining the films caused the remaining wrinkles to collapse into a discrete number of folds that is independent of film thickness and material properties.

Thesis advisor: Christopher Maxwell / This paper aims to measure the impact of increases to Seattle minimum wage from the years 2015 – 2018 on total earnings of the greater Seattle area. My research concentrates on low-wage industries but also touches upon the effect on high wage industries and the overall economy. Also, to ensure continuity of results, models were replicated at the federal level. This question is important because of a modern movement for higher state and city minimum wages. There have been several research papers about this topic already; however many economists have come up with conflicting results. My methods are a combination of previously used methods in an attempt to provide an unbiased analysis. In addition, research that has been released on this topic only covers the initial increases in minimum wage from 2015 – 2016. My research expands on this time frame and analyzes the impact of minimum wage increases from 2015 – 2018. My results show a statistically significant positive impact of minimum wage on total earnings for the greater Seattle area, not just for low-wage industries but also for the overall economy. These results show that a high minimum wage can be beneficial for the economy. / Thesis (BA) — Boston College, 2019. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Departmental Honors. / Discipline: Economics.