Experiments were conducted on ASTM A572 50 and A992 steel over a range of intermediate strain rates in order to determine material strength properties of structural members subjected to dynamic loadings. The yield and ultimate tensile stress (UTS) of the steels were determined at increasing strain rates using a hydraulic apparatus and compared to static values obtained from ASTM E8 standardized tensile experiments. Results revealed that A572-50 steel exhibited an increase in yield stress of up to 35% and UTS of up to 20% as strain rate increased from 0.002 to 2.0 s-1. A992 steel demonstrated a similar increase in yield stress of up to 45% and UTS of up to 20%. Ratios of dynamic-to-static strengths were used to develop dynamic increase factor curves spanning the range of strain rates studied. These curves provide designers with material property values required for accurate and economical design of protective structures.

No description available.

[pt] Para avaliação de movimentos de corridas de detritos em vertentes montanhosas, é necessária uma abordagem reológica através de modalegem consitutiva da massa de solo descendente. O modelo de Bingham é amplamente empregado na literatura de corridas, sendo seus parâmetros a viscosidade plástica e tensão de escoamento. Esta análise provê o entendimento da propagação do movimento dos detritos em campo, ao fornecer uma estimativa de sua velocidade, espessura e alcance. O presente trabalho apresenta uma proposta para determinação da tensão de escoamento e viscosidade de solos, através de ensaios de abatimento de tubo cilíndrico. A tensão de escoamento e a viscosidade foram determinadas em um reômetro rotaticonal, com base nas taxas de cisalhamento definidas nos ensaio de abatimento. Foram estudados dois solos naturais do Rio de Janeiro, com diferentes granulometrias e plasticidades. Os resultados experimentais obtidos são comparados com soluções analíticas da literatura, e mostram que deve-se ter cuidado na definição destes parametros reológicos com base apenas em dados relacionados a distribuição granulométrica dos solos. Como resultado, foi estabelecida uma relação entre teor de umidade, tensão de escoamento e viscosidade. Comparando os dados obtidos com resultados disponíveis na literatura, conclui-se que a metodologia desenvolvida pode fornecer uma maneira simples de avaliar parâmetros reológicos de solos para análises de corridas. / [en] To evaluate debris flow downhill movements, it is necessary a rheological approach through constitutive modelling the descendent moving mass. Bingham s model is widely employed in the debris flow literature, its input parameters being plastic viscosity and yield stress. Such analysis provides understandings of the propagation of the debris motion in the field, once it provides an estimate of its velocity, thickness and range area. The present study presents a proposal for the assessment of soil yield stress and plastic viscosity, by laboratorial testing on a cylindrical tube slump test. Through the definition of shearing rates in the slump tests, yield stress and viscosity were determined on a plate–plate rheometer. Two natural soils from Rio de Janeiro, Brazil, with differing grain size distribution and plasticity, were used in the investigation. The experimental results obtained are compared with analytical and semi empirical solutions from the literature, and show that care must be taken in defining viscosities based only on data related to grain size. Correlations were obtained concerning to soil moisture and shear rates, defined in the slump tests, and also between plastic viscosity and yield stress, defined in the rheometer tests. As a result, good relationships between water content and both yield stress and viscosity were established. Comparing the obtained data with other results available in the literature it is concluded that the developed experimental methodology may provide a simple way to evaluate rheological parameters of soils for debris flow analyses.

Workability has traditionally been used as one of the measures for controlling concrete mixture proportioning. This metric has provided limits on the water content in the concrete mixture for given aggregate size and type. The slump test, which is commonly used as an assessment of workability, is not adequate for characterizing the flow behaviour / rheology of fresh concrete. Studies have shown that Bingham's rheological properties, namely yield stress and plastic viscosity, provide good description of the flow behaviour of fresh concrete. In this thesis, an experimental program was designed on the basis of factorial design to evaluate the method of Cement Association of Canada for designing and controlling concrete mixture. The variables included in the mix design are water-cement ratio, water content, coarse aggregate size, silica fume, slag and bulk volume of coarse aggregate. In addition, Neuro-Fuzzy network has been adopted to correlate the current mixture proportioning method to the rheological properties of concrete. The network was constructed using experimental data tested in this study. Such correlation allowed the determination of water-cement ratio, water content, fine aggregate and coarse aggregate from compressive strength, yield stress and plastic viscosity. / Thesis / Master of Applied Science (MASc)

Yes / The principal aim of this paper is to investigate the effect of sand grading, surface morphology, and content on the rheological properties—that is, yield stress and plastic viscosity—of fresh mortar. Mortars were produced from four different types of sand at two volumetric cement-sand ratios of 1/0.9 and 1/0.6. Each blend was prepared with five water-cement ratios of 0.60, 0.55, 0.50, 0.45, and 0.40. The rheometer was used to determine yield stress and plastic viscosity parameters of each cement paste and mortar. Test results show that the relative yield stress and plastic viscosity of mortar to cement paste is inversely proportional to the excess paste thickness up to low values, below which the surface texture of sand particles becomes significant.

Magnetorheological (MR) fluids offer solutions to many engineering challenges. The success of MR fluid is apparent in many disciplines, ranging from the automotive and civil engineering communities to the biomedical engineering community. This well documented success of MR fluids continues to motivate current and future applications of MR fluid. One such application that has been considered recently is MR fluid devices for use in impact and other high velocity applications. In such applications, the fluid environment within the device may be well beyond the scope of our understanding for these fluids. To date, little has been done to explore the suitability of MR fluids in such high velocity and high shear applications. While future applications may expose the fluid to adverse flow conditions, we must also consider current and existing applications which expose the fluid to extreme flow environments. Consider, for example, an MR damper intended for automotive primary suspensions, in which shear rates may exceed 10^5 s^-1. Flow conditions within these dampers far exceed existing fluid behavior characterization. The aim of the current study is to identify the behavior of the fluid under these extreme operating conditions. Specifically, this study intends to identify the behavior of MR fluid subject to high rates of shear and high flow velocities. A high shear rheometer is built which allows for the high velocity testing of MR fluids. The rheometer is capable of fluid velocities ranging from 1 m/s to 37 m/s, with corresponding shear rates ranging from 0.14x10^5 s^-1 to 2.5x10^5 s^-1. Fluid behavior is characterized in both the off-state and the on-state. The off-state testing was conducted in order to identify the high shear viscosity of the fluid. Because the high shear behavior of MR fluid is largely governed by the behavior of the carrier fluid, the carrier fluid behavior was also identified at high shear. Experiments were conducted using the high shear rheometer and the MR fluid was shown to exhibit nearly Newtonian post-yield behavior. A slight thickening was observed for growing shear rates. This slight thickening can be attributed to the behavior of the carrier fluid, which exhibited considerable thickening at high shear. The purpose of the on-state testing was to characterize the MR effect at high flow velocities. As such, the MR fluid was run through the rheometer at various flow velocities and a number of magnetic field strengths. The term "dwell time" is introduced and defined as the amount of time the fluid spends in the presence of a magnetic field. Two active valve lengths were considered, which when coupled to the fluid velocities, generated dwell times ranging from 12 ms to 0.18 ms. The yield stress was found from the experimental measurements and the results indicate that the magnitude of the yield stress is sensitive to fluid dwell time. As fluid dwell times decrease, the yield stress developed in the fluid decreases. The results from the on-state testing clearly demonstrate a need to consider fluid dwell times in high velocity applications. Should the dwell time fall below the response time of the fluid, the yield stress developed in the fluid may only achieve a fraction of the expected value. These results imply that high velocity applications may be subject to diminished controllability for falling dwell times. Results from this study may serve to aid in the design of MR fluid devices intended for high velocity applications. Furthermore, the identified behavior may lead to further developments in MR fluid technology. In particular, the identified behavior may be used to develop or identify an MR fluid well suited for high velocity and high shear applications. / Ph. D.

Les fluides à seuil ont des propriétés mécaniques étonnantes : en dessous d'une certaine contrainte, appelée contrainte seuil, le fluide se comporte comme un solide. Au-delà de la contrainte seuil, ils s'écoulent comme un gel. Ce mémoire porte sur l'étude des actions des forces magnétiques volumiques sur ces fluides. Nous étudions la possibilité de réaliser la transition solide-gel à partir des forces magnétiques volumiques créées par différents dispositifs magnétiques. Ces fluides n'ont pas de propriétés magnétiques particulières. Il est donc nécessaire de créer des champs magnétiques intenses pour agir sans contact sur ces fluides. Nous étudions différentes configurations magnétiques capables de dépasser la contrainte seuil au sein du fluide. L'influence des différents paramètres des configurations magnétiques est explorée, notamment à l'aide d'études paramétriques. Notre travail mêle des équations de magnétostatique et de mécanique des fluides non-newtoniens. Les calculs de magnétostatique sont menés de façon analytique alors que la partie mécanique et le couplage magnéto-mécanique sont traités par un logiciel de simulation numérique par la méthode des éléments finis. Les conditions magnétiques et mécaniques nécessaires à la transition solide-gel et à la modification d'écoulements de fluides à seuil sont discutées, notamment à l'aide de simulations numériques et de nombres adimensionnels / Yield stress fluids have amazing mechanical properties: below a particular shear stress, called yield stress, the fluid behaves like a solid. Once the yield stress is exceeded, they flow like a viscous fluid or a gel. This thesis deals with the effects of magnetic volume forces on these fluids. We study the opportunity of the solid-gel transition from magnetic volume forces created by various magnetic devices. These fluids have no special magnetic properties. It is therefore necessary to create intense magnetic fields to act without contact on these fluids. We study different magnetic configurations that are able to exceed the yield stress in the fluid. The influences of different parameters of the magnetic configurations is explored, including using parametric studies. Our work combine equations of magnetostatic and non-newtonian fluid mechanics. Magnetostatic calculations are carried out analytically, while the mechanical and magneto-mechanical coupling are processed by a finite element analysis software. Magnetic and mechanical conditions required to the solid-gel transition and to the modification of yield stress fluids flows are discussed, using numerical simulations and dimensionless numbers

Au cours de ce travail, nous nous sommes attachés à prédire les caractéristiques rhéologiques de suspensions de particules dans des situations non newtoniennes. Nous avons tout d'abord étudié expérimentalement le comportement rhéologique de suspensions bidisperses de particules non colloïdales et non browniennes immergées dans un fluide à seuil dans les situations où les interactions entre particules sont hydrodynamiques (mécaniques). Nous avons montré que l'influence de la polydispersité des particules sur le module élastique et le seuil de contrainte de la suspension pouvait être décrit en utilisant un modèle d'empilement développé pour les matériaux granulaires secs. Deux relations analytiques simples permettant d'estimer le module élastique et la contrainte seuil d'une suspension non newtonienne polydisperse en fonction des caractéristiques des constituants ont alors été proposées et validées. Nous nous sommes ensuite intéressés à la prédiction des caractéristiques globales de suspensions contenant une forte concentration de particules de taille différente dans le cadre d'une approche par changement d'échelle. Pour cela, nous avons mis en uvre une approche par motifs morphologiques permettant la prise en compte de paramètres géométriques tels que la distribution de tailles des inclusions ou les distances entre particules voisines. Les résultats de ce modèle ont été validés par comparaison avec des données expérimentales de la littérature. Nous avons ensuite montré que les modèles morphologiques permettaient également de décrire l'évolution des modules complexes d'un matériau thixotrope subissant une transition de phase liquide-solide due à la croissance et la percolation d'un réseau de particules attractives. Dans la dernière partie de cette étude, nous avons étudié expérimentalement l'influence de l'histoire de cisaillement sur la structuration et la déstructuration d'une suspension colloïdale thixotrope / In this work, we aimed to predict the rheological properties of suspensions of particles in non-Newtonian fluids. We first studied experimentally the rheological behaviour of bidisperse suspensions of non colloidal particles and non-Brownian immersed in a yield stress fluid in situations where interactions between particles are hydrodynamic (mechanical). We showed that the influence of the polydispersity on the elastic modulus and yield stress of the suspension could be described using a packing model developed for dry granular materials.Two simple closed form estimates for both the elastic modulus and the yield stress of non-Newtonian polydisperse suspension as a function of the characteristics of the constituents were proposed and validated. This study was then extended in a micromechanical analytical framework to predict the macroscopic characteristics of suspensions containing highly concentration of particles with different size. Our ne w model, called a "Morphologically Representative Pattern - Based Approach" (MRP-based approach), successfully predicts the behaviour of such materials by taking into account some geometrical parameters such as the particle size distribution or the distance between the nearest-neighbour particles. This model has been validated by a comparison with the experimental data in the literature. We then showed that the MRP-based approach also allowed describing the evolution of complex modules of a thixotropic material undergoing a liquid-solid transition due to the growth and the percolation of an attractive particle network. In the last part of this work, we studied experimentally the influence of the flow history on the structure of a thixotropic colloidal suspension

Le comportement (écoulement, adhésion,…) d'un fluide à seuil le long d'une surface solide est un problème récurrent dans de nombreux procédés industriels. Le caractère non newtonien de ce type de matériau rend difficile l'application des concepts établis dans le cas des écoulements similaires de liquides simples. Dans cette thèse, nous étudions expérimentalement ce problème en analysant l'écoulement généré le long d'une plaque solide en mouvement vertical (enfoncement et retrait) uniforme à travers un fluide à seuil simple. Nous déterminons d'abord le lien entre la force mesurée le long de l'objet et les propriétés rhéologiques du matériau. Nous en déduisons une nouvelle technique pour mesurer la contrainte seuil de ces matériaux. Nous décrivons, ensuite, les caractéristiques locales de l'écoulement généré lors de la pénétration de la plaque. Nous montrons que l'écoulement est localisé autour de l'objet, dans une couche d'épaisseur uniforme alors que le reste du fluide est déformé mais reste dans son état solide. Nous décrivons le processus par lequel cette couche limite se développe et nous déterminons la répartition des zones solides/ liquides autour de l'objet. Enfin, nous étudions les effets de mouillage et d'adhésion sur la plaque. En particulier, nous présentons une approche expérimentale permettant d'évaluer la tension de surface des fluides à seuil / The behavior (flow, adhesion,...) of a yield stress fluid along a solid surface is a recurrent problem in many industrial processes. The non-Newtonian character of this type of material makes it difficult to apply the concepts established in the case of similar flows of simple liquids. In this thesis, we study this problem experimentally by analyzing the flow generated along a solid plate moving vertically (penetration and withdrawal) through a simple yield stress fluid. We first determine the relationship between the measured force along the object and the rheological properties of the material. We derive a new technique for measuring the yield stress of the material. We describe then the local characteristics of the flow generated during the penetration of the plate. We show that the flow is located around the object in a layer of uniform thickness, while the rest of the fluid is deformed but remains in its solid state. We describe the process by which the boundary layer develops and determine the distribution of solid / liquid zones around the object. Finally, we study the effects of wetting and adhesion on the plate. In particular, we present an experimental approach to evaluate the surface tension of a yield stress fluid

Il est possible de modifier la composition des bétons utilisés dans le domaine de la construction pour réduire sensiblement le dégagement de CO2 associé à leur fabrication. Ceci est obtenu en réduisant significativement la quantité de clinker et en incorporant des matériaux de substitution appelés additions. Elles sont généralement moins réactives et demandent, pour maintenir un niveau acceptable de performances mécaniques et de durabilité, une réduction importante du dosage en eau. C'est le cas des bétons à faible impact environnemental. L'utilisation de superplastifiant dans ces bétons permet d'augmenter leur fluidité mais leur viscosité plastique reste toujours élevée ce qui induit des problèmes de mise en œuvre. La maîtrise de la viscosité plastique de ce type de béton est donc cruciale pour le développement de ces produits.Avec cet objectif fixé, dans la première partie de cette étude, un rhéomètre à béton, adapté aux spécificités des bétons à faible impact environnemental, a été développé. Associé à un protocole d'essai pertinent cet appareil permet de caractériser le comportement rhéologique non seulement des bétons courants mais également des bétons à faible impact environnemental.Ensuite, l'utilisation de ce rhéomètre dans un programme expérimental a permis de mettre en évidence l'effet des paramètres de compositions et notamment le taux de substitution et la nature des additions sur leur comportement rhéologique.Les résultats obtenus à partir de ce programme ont permis de proposer et valider un modèle de calcul de la viscosité plastique en considérant que le béton est constitué de deux échelles : pâte et granulats. Le modèle est applicable pour les bétons ordinaires et pour les bétons à faible impact environnemental. Une méthode d'optimisation de la viscosité a été proposée à l'aide du modèle. / It is possible to modify the composition of conventional concrete used in the building field in order to reduce the emission of CO2 associated with their manufacture, particularly in the production of their constituents. This is can be achieved by significantly reducing the amount of clinker and incorporating alternative materials (mineral and chemical additions), which are generally have a lower reactivity and require a low quantity of water, with an adequate level of mechanical performance and durability. This is the case of concrete with low environmental impact. The use superplasticizer in the production of concrete allows increasing their flowability, despite the using of low content of water, but their plastic viscosity remains high and may cause problems of implementation. Controlling the plastic viscosity of this type of concrete is crucial to ensure the development of these products.Within this objective, a rheometer for concrete was developed. The relevant test protocol used for this apparatus enables to characterize the rheological behavior not only for conventional concrete, but also for concrete with low environmental impact.The use of the developed rheometer within an experimental program permits then to highlight the effect of the parameters of concrete compositions, and in particular the used additions (type and rate of substitution) on their rheological behavior.The obtained results from this program propose and validate a mathematical model for assessing the plastic viscosity, which is applicable for ordinary concrete and concrete with low environmental impact. An optimization method for calculating the plastic viscosity of the concrete has been proposed using this model.