This dissertation proposes a modi ed internal state variable (ISV) inelastic damage model that was motivated by experimental structure{property relations of thermoplastics. In particular, a new damage model was developed for glassy, amorphous thermoplastics. ISV evolution equations are de ned through thermodynamics, kinematics, and kinetics for isotropic damage arising from two di erent inclusion types: pores and particles. The damage arising from the particles and crazes is accounted for by three processes: damage nucleation, growth, and coalescence. Damage nucleation is de ned as the number density of voids/crazes. The associated ISV rate equation is a function of stress state, molecular weight, fracture toughness, particle size, particle volume fraction, temperature, and strain rate. The damage growth is based upon a single void growing and its growth is de ned by an ISV rate equation that is a function of stress state, strain rate sensitivity, and strain rate. The coalescence ISV equation enables interaction between voids and crazes and is a function of the nearest neighbor distance between voids/crazes, size of voids/crazes, temperature, and strain rate. The damage arising from pre-existing voids employs the Cocks{Ashby void growth rule. The total void volume fraction is a summation of the damage arising from particles, pores, and crazes. Micromechanical modeling results for a single void compare well to experimental ndings garnered from the literature. This formulation is then implemented into a nite element analysis. For damage evolution, comparisons are made between a one-dimensional material point simulator and a three-dimensional nite element (FE) simulation. Finally, good agreement is found between impact experiments and FE impact simulations using the implemented model.

Masonry is an orthotropic material that exhibits distinct directional properties due to the existence of mortar joints acting as planes of weakness. Therefore, a constitutive model employed in the numerical analysis should be capable of describing the anisotropic behavior. The main objective of this research is to implement a macroscopic failure criterion which describes the failure conditions in structural masonry. For this purpose, a comprehensive framework is outlined for modelling of the mechanical behaviour of structural masonry. In this framework, the anisotropic material properties are described using the microstructure tensor approach (Pietruszczak and Mroz, 2001). Then, a mathematical formulation defining the conditions at failure is discussed. The formulation contains several material parameters as well as material functions that describe the anisotropic behaviour. The identification procedure for these functions is outlined and is verified using the experimental tests conducted by Page (1983). Later, an extensive numerical study, including a set of numerical simulations of biaxial compression-tension and biaxial compression tests for different bedding plane orientations, is conducted to evaluate the performance of the proposed macroscopic failure criterion. In the last part of the thesis, some 3D finite element simulations of a shaking table test are performed involving a reduced scale model of four storey masonry building subjected to seismic excitation. A linear dynamic analysis, in which the proposed macroscopic failure criterion is incorporated through the UMAT subroutine, is carried out to assess the plastic admissibility of the stress field. The results including the distribution of the value of the failure function are then compared with the crack pattern in the experimental test. / Thesis / Master of Applied Science (MASc)

No / Thermoforming is widely employed in industry for the manufacture of lightweight, thin-walled products from pre-extruded plastic sheet and its largest application is in packaging. Over many years attempts have been made to simulate the process and thereby exploit modern computational tools for process optimisation. However, progress in this area has been greatly hampered by insufficient knowledge of the response of polymer materials under thermoforming conditions and an inability to measure this and other processing phenomena accurately. In recent years some address has been made to these problems through advances in measurement technologies, and in particular, the development of high speed, high strain, biaxial testing machines that are designed to replicate the conditions in thermoforming processes. In this work the development of an advanced finite element-based thermoforming process simulation is presented. At its heart is a sophisticated large strain thermally coupled (LSTC) material model for polypropylene, which has been developed after several years of research and is founded directly on biaxial test results at elevated temperatures. This material model has been demonstrated to provide an excellent fit to the biaxial data and to offer a very stable computational platform for the process simulation.The performance of the working simulation was validated through comparison with matching experimental test results, and this enabled investigation of the sensitivity of the process output (in the form of part wall thickness distribution) to changes in a range of other processing parameters. This work confirmed that the process is most sensitive to the parameters controlling plug/sheet contact friction. Heat transfer parameters were also shown to be significant and the requirement for the model to be fully thermo-mechanically coupled has been clearly established.

Polymer matrix composites are seeing increasing use in structural systems (e.g. ships, bridges) and require a quantitative basis for describing their performance under combined mechanical load and fire. Although much work has been performed to characterize the flammability, fire resistance and toxicity of these composite systems, an understanding of the structural response of sandwich type structures and laminate panels under combined mechanical and thermal loads (simulating fire conditions) is still largely unavailable. Therefore a research effort to develop a model to describe the structural response of these glass/vinyl esters systems under fire loading conditions is relevant to the continuing and future application of polymer matrix composites aboard naval ships. The main goal of the effort presented here is to develop analytical models and finite element analysis methods and tools to predict limit states such as local compression failures due to micro-buckling, residual strength and times to failure for composite laminates at temperatures in the vicinity of the glass transition where failure is controlled by viscoelastic effects. Given the importance of compression loading to a structure subject to fire exposure, the goals of this work are succinctly stated as the:(a)Characterization of the non-linear viscoelastic and viscoplastic response of the E-glass/vinyl ester composite above Tg. (b)Description of the laminate compression mechanics as a function of stress and temperature including viscoelasticity.(c)Viscoelastic stress analysis of a laminated panel ([0/+45/90/-45/0]S) using classical lamination theory (CLT). Three manuscripts constitute this dissertation which is representative of the three steps listed above. First, a detailed characterization of the nonlinear thermoviscoelastic response of Vetrotex 324/Derakane 510A - 40 through Tg was conducted using the Time - Temperature - Stress - Superposition Principle (TTSSP) and Zapas - Crissman model. Second, the modeling approach and viscoelastic relaxation mechanism is validated by substituting the shear relaxation modulus into a compression strength model to predict lifetimes for isothermal and one sided heating of unidirectional laminates. Finally, viscoelastic stress analysis using CLT is performed for a general laminated panel to predict lifetimes under one sided heating. Results indicate that when temperatures remain in the vicinity of Tg, the laminate behavior is controlled by thermoviscoelasticity. / Ph. D.

Sprains are the most common injuries to ligamentous tissues. They are classified as first-degree, second-degree, or third-degree sprains depending upon their severity. First-degree sprains are the result of over-stretching of ligaments. Second-degree sprains involve partial tears of the ligaments. In third-degree sprains, the ligaments are completely torn. Although first- and second-degree sprains are not as severe as third-degree sprains, they occur more frequently. The mechanisms leading to sprains are still not well understood. Therefore, histo-mechanical experiments and theoretical studies are needed to advance our current knowledge on the etiology of sprains. In the first part of this study, a structurally-based constitutive equation is proposed to simulate the damage evolution process in ligaments. The ligament is modeled as a bundle of crimped collagen fibers that are assumed to be oriented along one direction, the physiological loading direction. The gradual straightening of collagen fibers determines the nonlinearity in the toe region of the tensile axial stress-strain curve. Straight collagen fibers behave as a linear elastic material. The gradual damage of collagen fibers determines the nonlinearity in the failure region of the tensile axial stress-strain curve. The parameters in the constitutive equation are estimated by curve fitting experimental data on rat medial collateral ligaments (MCLs) published in the biomechanics literature. In the second part of this study, mechanical experiments are performed in order to identify and quantify damage in ligamentous tissues. MCLs, which are harvested from Sprague-Dawley (SD) rats, are subjected to displacement controlled tensile tests. Specifically, the ligaments are stretched to consecutively increasing stretch values until their complete failure occurs. The elongation of the toe region and decrease in tangent modulus of the linear region of the collected stress-strain data are analyzed and two significantly different damage threshold strains are determined. The effect of age and skeletal maturation on the damage evolution process is also investigated by performing mechanical tests on MCLs isolated from two age groups of SD rats. In the third part of this study, scanning electron microscopy (SEM) is used to determine variations in the microstructure of ligaments that are associated with the elongation of the toe region and decrease in tangent modulus of the linear region of the stress-strain curve. MCLs from SD rats are subjected to different threshold strains that produce damage and, subsequently, examined using SEM. By comparing the morphology of collagen fibers and fibrils in undamaged and damaged MCLs, the microscopic variations induced by strain are determined and correlated to the observed macroscopic mechanical damage. / Ph. D.

Reinforced Concrete (RC) structures are common in earthquake-prone areas. During an earthquake, the steel reinforcement is subjected to cyclic strain histories which lead to inelastic response. In the case of rare, strong earthquakes, inelastic buckling and even rupture due to low-cycle fatigue can also occur. The understanding and characterization of the performance of RC structures under earthquake hazards requires the accurate simulation of the inelastic hysteretic behavior of steel reinforcement by means of appropriate constitutive models. Several uniaxial material models have been developed for reinforcing steel. Existing material models sacrifice efficiency for accuracy or vice versa. Conceptually simple and numerically efficient models do not accurately capture the hysteretic response and ignore rupture or buckling. On the other hand, more refined material models are characterized by iterative stress update procedures which can significantly increase the computational cost of an analysis. Additionally, experience suggests that refined models attempting for the effect of inelastic buckling tend to lead to numerical convergence problems in the stress update procedure. The goal of the present study is the formulation and implementation of an accurate and computationally efficient constitutive model for steel reinforcement under cyclic loading. A previously developed model, capable of capturing the inelastic hysteretic response of reinforcing steel in the absence of buckling and rupture, is used as a starting point in this study. The model is enhanced by replacing its original, iterative stress update procedure with an equally accurate, non-iterative one. Additionally, the model is enhanced to capture the effects of inelastic buckling and of rupture. The accuracy of the model and the efficiency of the non-iterative stress update algorithm are demonstrated by means of validation analyses. / Master of Science

Eve Ensler's goal in writing The Vagina Monologues was to generate a dialogue regarding women's sexuality to counter the silence that pervades the patriarchal culture that they inhabit. To achieve this goal, Ensler constructs two ideologies—one grounded in patriarchy and another supposedly grounded in female agency and dialogue—to reveal the problems within the current ideology in hopes that her audience will adopt her new ideology and resolve the detrimental silence women endure. To evaluate its success, this study utilizes an eclectic approach—comprised of constitutive rhetoric, second persona, third persona, and bell hooks' rhetorical options—to determine if the play's content encourages the dialogue Ensler desires. / Master of Arts

Le rapport à l'autre a lieu dans la concrétude de l'éthique et de l'érotique ; par ailleurs, il se réalise à travers des dispositifs techniques. Nous voudrons ici confronter la phénoménologie/éthique lévinassienne à une pensée de la technique comme constitutive et constituante. En particulier, nous chercherons à faire entrer en dialogue les descriptions de la révélation du visage, d'une part, et, d'autre part, une description fonctionnelle de la corporéité allant jusqu'à prendre en considération son déploiement dans l'outil saisi. L'augmentation technique des corps éthiques sera décrite comme l'affirmation d'un écart entre l'appel et les possibilités de la réponse, écart dans la responsabilité même. Finalement, c'est dans une lecture croisée de Lévinas avec l'analytique existentiale heideggerienne, que nous dégagerons une description de la subjectivité comme la réalisation du pour-l'autre par un être-au-monde. / The relation to the Other takes place in the concreteness of ethics and erotic relations ; in addition, this relation is quite generally mediated through technological devices. Here, we will confront the phenomenology and ethics of Levinas with a vision of technology as anthropologically constitutive and constituting. In particular, we will seek to set up a dialogue between the revelation of the face, on the one hand, and on the other hand a functional description of embodiment that takes into account its technological augmentation through the use of tools. The technological augmentation of ethical bodies will be described as involving an irreducible gap between the appeal from the other and the possibility of responding, a gap within the very domain of responsibility itself. Finally, by means of a comparative reading of Levinas with the existential analytics of Heidegger, we will arrive at a description of subjectivity as consisting in the accomplishment by a being-in-the-world of existing for-the-other.

La chromatine embryonnaire subit des changements nécessaires pour l’établissement d’un nouveau programme développemental. Ce travail a étudié l’organisation de l’hétérochromatine au cours du développement sous trois facettes. La première étant celle de d’hétérochromatine constitutive, à travers, l’établissement forcé de la marque H4K20me3 qui provoque un arrêt du développement préimplantatoire. Ce phénotype dépend spécifiquement de l’activité de la methyltransferase SUV4-20h2 et induit l’activation de la voie de signalisation ATR qui bloque la phase de réplication. En deuxième partie, l’hétérochromatine facultative a été le sujet d’une analyse de l’expression des protéines du complexe non-canonique PRC1 et de la modification H2AK119ub qui en résulte. Finalement, une analyse de la chromatine embryonnaire a été mise en place et a permis la détection des changements de niveau de compaction au cours du développement préimplantatoire. / Embryonic chromatin undergoes necessary changes to establish a new developmental program. This work has addressed the organization of heterochromatin in preimplantation embryos from three angles. The first part probed the absence of constitutive heterochromatin by forcing the establishment of the H4K20me3 mark which results in an embryonic arrest prior to the 2-cell stage. This phenotype is due to the specific histone methyl-transferase activity of SUV4-20h2 and is induced by ATR activation which blocks replication. In the second part, facultative heterochromatin was studied by analyzing the levels of several members of the non-canonical PRC1 complex as well as the resultant modification H2AK119ub. Finally, an analysis of the embryonic chromatin was set up and allowed for the measurement of changes in the chromatin openness during preimplantation development.

Les matériaux granulaires exhibe un spectre très large de propriétés constitutives, le long de chemins de chargement très divers. Développer des modèles constitutifs permettant de reproduire ces caractéristiques a demeuré un réel challenge scientifique au cours des dernières décennies. A cet égard, les approches multi-échelles constituent aujourd’hui une voie très prometteuse. Elles permettent de relier les propriétés macroscopiques à celles observées à l’échelle microscopique.Une investigation a été menée sur la base de simulations numériques discrètes (DEM)d’essais biaxiaux, afin d’identifier les caractéristiques micro-structurelles du matériau granulaire, la manière dont elles évoluent au cours d’un chemin de chargement, et le rôle qu’elles jouent dans l’émergence du comportement macroscopique. A l’échelle mésoscopique,le réseau de transmission de force (chaines de force) et les cellules définies parles vecteurs branches (meso-cycles) apparaissent jouer un rôle de première importance.Les meso-cycles, construits à partir du réseau de contact de l’assemblage, peuvent être caractérisés en fonction du nombre de cotés qu’ils contiennent (topologie). Leur influence sur le comportement volumique de l’échantillon est en effet étroitement liée à ce nombre de contact. En outre, leur interaction avec les chaines de force est également fortement dépendante de leur topologie. Ainsi, les cycles contenant 3 cotés (L3) participent activement à la stabilisation des chaines de force, alors que les cycles contenants au moins6 cotés (L6+) contribuent essentiellement au comportement dilatant de l’échantillon et à l’effondrement des chaines de force. Enfin, l’existence d’une méso-structure unique à l’état critique, au sein de la bande de cisaillement (rupture localisée) ou au sein de l’échantillon (rupture diffuse), est clairement démontrée.viii Sur la base de ces résultats, un modèle constitutif a été développé à partir du modèle H-directionnel (Nicot and Darve, 2011b). La structure du matériau granulaire est décrite par un assemblage d’hexagones (modélisant les cycles L6), orientés dans toutes les directions de l’espace. A partir d’opérations d’homogénéisation, les contraintes et les déformations incrémentales peuvent être reliées à l’échelle de l’assemblage, donnant lieu à un modèle de comportement dont la performance a pu être testée le long de chemins de chargements variés. / Granular materials exhibit a wide spectrum of constitutive features under various loading paths. Developing constitutive models which succeed to characterize these features has been challenging scientists for decades. A promising direction of achieving this can be the multi-scale approach. Through which the constitutive model is formulated in the way that relating material's macroscopic properties to their micro-scale essences, namely, corresponding micro-structure properties.To better characterize the micro-structure and formulate the relation between different scales, a comprehensive investigation have been carried out on the basis of numerical biaxial tests using 2D discrete element method (DEM), in order to ascertain the micro-structure characteristics of the granular material, the way they evolve versus loading and their corresponding rules in the macroscopic behaviors. In a meso-scale, intermediate between the single contact scale and the macro-scale, the force transmission network (force-chains) and area element enclosed by contacts branches (meso-loops) are highlighted in terms of their significant influences on material's macro-scale behavior. Meso-loops herein are tessellated from the whole area of the granular assembly by the contact branch network, and are subsequently categorized according to their side number.The development of meso-loops is observed to be intimately related to material's volumetric evolution, especially the plastic part. Then, the interaction between force-chains and meso-loops and its significance to the global volumetric behavior are revealed. Otherwise, in critical state, an identical meso-structure is found in the failure area of both localized and diffuse failure mode. Meso-loops with 3 sides (L3) appear to be indispensable for the force-chain stability, meanwhile, meso-loops with more than or equal to 6 sides (L6+) contribute much to the volume expansion and accelerate the force-chain buckling. The interplay between L3 and L6+ largely embody, or are representative of, the various mechanical performance of the granular material.A constitutive model has been developed by modifying the H-directional model. In this model, individual hexagons, representatives of L6+, construct the fabric as distributing along different directions in the space. Then multi-scale approach is then used to relate macroscopic properties from local ones, and eventually, to give the constitutive relation. This model is then validated in different loading paths, and eventually proved satisfying.