The literature indicates that mortar strength has little influence on concrete masonry strength, suggesting that the fresh state properties of the mortar are more relevant than the properties of the hardened mortar, and this point of view is reflected on standards and codes. However, the failure mode of the masonry can be dramatically influenced by the properties of the hardened bedding mortar especially when using a mortar with low compressive strength. In such case, mortar crushing can be the masonry failure mode. This study evaluated the influence of bedding mortar on the failure modes of axially loaded masonry through three distinct approaches. The first approach was a visual analysis that used pictures from a high-definition camera to determine the rupture sequence of masonry prisms. The analysis used pictures from tests of four different prism assemblages. The prisms were two and three blocks high with stack-bond and running-bond configurations and constructed with three types of blocks: concrete blocks and hollow and solid walls ceramic blocks. Two mortar types with different strengths were used to assemble the prisms. The visual analysis indicated that mortar crushing happens and completely changes the masonry failure mode. The second approach evaluated the stress-strain behavior of small thickness axially loaded mortar samples with the objective of capturing changes in the mechanical properties of the mortar. The properties of interest were the Poisson’s ratio, volumetric strain, and strain increments. The evaluation demonstrated that crack propagation near failure results in changes on the mechanical properties of the mortar and that those changes can be used as a measure of the degradation of the mortar. The third approach was the development of a finite element model to represent the axially loaded mortar samples. The model used a phased analysis, which allowed the elastic modulus and Poisson’s ratio of the material to be changed during the loading sequence. The nonlinear model was able to capture the strain changes on the confined mortar. / É comum no meio técnico a ideia de que a resistência da argamassa de assentamento tem pouca influência sobre a resistência da alvenaria, devendo-se valorizar mais o desempenho da argamassa no estado fresco do que no endurecido. Essa forma de pensamento reflete-se, ainda, em alguns textos normativos que regem o projeto de edificações em alvenaria estrutural. No entanto, quando analisado também o modo de ruptura da alvenaria, percebe-se que as propriedades da argamassa no estado endurecido podem alterar completamente a dinâmica de propagação de dano na alvenaria, em especial quando a argamassa de assentamento é de baixa resistência e sujeita a sofrer o esmagamento quando carregada. Este estudo buscou avaliar como a argamassa de assentamento influencia o modo de ruptura da alvenaria estrutural através de três diferentes abordagens. A primeira foi a análise visual, através de sequências quadro a quadro, da ruptura de prismas comprimidos axialmente. Foram avaliadas diferentes geometrias de prismas, com duas ou três fiadas de altura, com ou sem juntas verticais; três tipos de blocos, cerâmicos de paredes vazadas, cerâmicos de paredes maciças e blocos de concreto; e argamassas de alta e baixa resistência. Observou-se nessa abordagem que a argamassa de assentamento pode sofrer esmagamento e alterar o modo de ruptura da alvenaria. A segunda abordagem adotada foi a de avaliar o comportamento tensão-deformação de corpos-de-prova de argamassa com pequena altura sujeitos à compressão confinada, buscando identificar alterações em propriedades como coeficiente de Poisson, variação volumétrica específica e incrementos de deformação. A análise desses resultados demonstrou que a propagação de trincas no material próximo a ruptura altera as propriedades mecânicas e pode ser usada como uma medida do avanço da degradação. Por fim, a terceira abordagem buscou viabilizar um modelo numérico em elementos finitos capaz de considerar a propagação de trinca através da variação do módulo de elasticidade e coeficiente de Poisson. O modelo incremental por fases foi capaz de reproduzir de maneira satisfatória o comportamento de corpos-de-prova de argamassa comprimidos.

This dissertation presents an investigation of the effects of stress, and of absolute and relative particle size, in tests on vertically loaded footings. Two granular materials, namely, a silica rock flour and a Chatelet flint grit, which differed in nominal diameter by a factor of 50 but were otherwise practically similar in all other grain characteristics were used in this work. A comprehensive series of triaxial tests under a wide range of cell pressures was carried out to quantify the stress and absolute particle size effects. Model footing tests were also performed by pushing a rigid circular punch axisymmetrically into the flat surface of a cylindrical soil model either under 1-g (gravity) with surcharge or under elevated g in a centrifuge. The 1-g and centrifuge test series were used to study the scale effects on the surcharge term Ng and the self-weight term Nγ of the Terzaghi bearing capacity equation, respectively. Parameters varied were punch diameter, particle size and surcharge or g level. Two theoretical analyses were attempted based on the finite element method and the method of characteristics. Using the Schofield Soil Model, the finite element analysis can give a reasonable order of magnitude prediction for the settlement of the footing under working load conditions. When the effect of reducing angle of shearing with increasing stress was taken into account together with the change of geometry due to footing penetration, the angles of shearing inferred from the method of characteristics fall within ±20 of those measured in triaxial compression tests. Distortion due to violating the scaling law by not conserving the ratio of particle size to model dimension was not considered to be significant. Distortion due to violating the constitutive soil behaviour by varying the absolute particle size was found to be significant due to differences in grain crushing, but this can be accounted for effectively by the new style of calculations developed in the thesis.

This diploma thesis is concerned with a construction design of single toggle jaw crusher DCJ 900x500. In the first part, the theoretical background and ways of material disintegration are discussed. The second chapter describes types of material crushers in general, especially jaw crushers and their parts. The third chapter is concerned with calculations and the design of the most important parts of the machine. The fourth part consists of the crusher power calculation, design of the pendulum and its production technology. The last part includes the result of FEM analysis for the particular variant of pendulum production. The thesis also includes drawing documentation of the crusher and the pendulum.

Dans l’optique de la conception et du développement d’un siège aéronautique et afin derespecter la règlementation sécuritaire en vigueur, la structure du siège développé doitpermettre une dissipation rapide de l’énergie perçue en cas de crash aérien (Fig. 1), ceci dansle but de protéger les passagers. La majorité des systèmes intégrés à la structure des sièges etpermettant cette absorption d’énergie (Fig. 2) est constituée de composants métalliques qui sedéforment plastiquement pour dissiper l’énergie due au crash. Actuellement, l’industrie et larecherche se tournent vers les matériaux composites pour substituer de tels systèmes.Cependant le comportement de ces matériaux lors de sollicitations mécaniques sévères estfortement différent des matériaux métalliques, notamment dû au fait que les mécanismesd’endommagement sont très distincts.Le but de cette étude portant sur des structures tubulaires composites est d’évaluer leurcapacité à dissiper l’énergie. A cette fin, différentes stratifications ont été testées encompression (Fig. 3 et 4) dans le but de déterminer leur comportement, comparer leurspropriétés et calculer leurs valeurs de SEA (absorption d'énergie spécifique, en kJ.kg-1)servant à évaluer leur aptitude à dissiper l’énergie engendrée en cas de crash. Ces dernièressont issues des courbes effort-déplacement obtenues lors des essais d’écrasement (Fig. 5). Lesdifférents essais de compression ont été instrumentés et suivis au moyen de caméras rapides etdes images post-essais ont été réalisées par tomographie pour comprendre les mécanismesd’endommagement mis en jeu (Fig. 4 et 6). Ces essais ont été réalisés à vitesse de chargementquasi-statique puis dynamique et selon diverses conditions limites. Les différents résultats decomportement en compression sont également utilisés dans le but de construire et enrichir unmodèle de calcul par éléments finis (Fig. 7 et 8) permettant de simuler la réponse de structurescomposites de différentes natures soumises au crash en intégrant la géométrie et lacomposition de la structure (Fig. 8).L’objectif de ce travail de recherche est ainsi d’évaluer l’énergie pouvant être dissipée par desstructures tubulaires composites, de comparer les absorptions induites par des structurescomposites de compositions différentes, et/ou bi-matériaux, et enfin de fournir un modèleéléments finis représentant le comportement de structures composites en compression jusqu’àl’endommagement et la ruine de la structure.Il a ainsi été établi qu’en chargement statique, un stratifié unidirectionnel orienté à 0° etstabilisé par des plis de tissus répond fortement aux attentes en terme de dissipation d’énergie,mais pas en sollicitation dynamique. Dans ce cas, une stratification à 90° semble plusadéquate. D’autre part, un confinement forcé vers l’intérieur est avantageux dans la plupartdes cas, réduisant le pic d’effort initial sans diminuer drastiquement la valeur de SEA. / With the perspective of the design and development of an aircraft seat and in order to respectthe safety regulations in effect, the structure of the developed seat must allow for a swiftdissipation of the energy received in the event of an aircraft crash (Fig. 1) so as to protect thepassengers. The majority of systems integrated into the seats structure and allowing energydissipation (Fig. 2) consists of metal components that sustain plastic deformation to dissipatethe energy induced by the crash. Currently, industry and research sectors are turning theirfocus towards composite materials to substitute such systems. However, the behavior of thesematerials during severe mechanical stress is strongly different from metallic materials, inparticular due to the fact that damage mechanisms are very distinct.The purpose of this study on composite tubular structures is to evaluate their ability todissipate the energy. To this end, different laminate structures were tested in compression(Fig. 3 and 4) in order to identify their behavior, compare their properties and calculate theirSEA value (Specific Energy Absorption, in kJ.kg-1) used to evaluate their capacity to dissipatethe energy generated during a crash. Those are resulting from the load-displacement curvesobtained during the crushing tests (Fig. 5). The various compression tests were instrumentedand monitored by means of rapid imaging cameras and post-crushing tomographic imaginghas been realized in order to understand the damage mechanisms involved (Fig. 4 and 6).Testing has been carried out under quasi-static and dynamic loading and using severalboundary conditions. The different results of compression and crushing behavior are also usedin order to build and improve a finite element calculation model (Fig. 7 and 8) allowing tosimulate the response of composite structures of different natures subjected to crash byintegrating the geometry and the composition of the structure (Fig. 8).The objective of this research work is thus to evaluate the energy that can be dissipated bycomposite tubular structures, to compare the absorption values induced by compositestructures of different compositions, and/or bi-materials, and, finally, to provide a finiteelement model representing the behavior of composite structure submitted to compressionuntil damage and fracture of the structure.It has consequently been established that in static loading, a unidirectional laminate orientedat 0° and stabilized by woven plies strongly meets the expectations in terms of energydissipation, but that is not the case in dynamic loading. In this case, a 90° stratification seemsmore adequate. Incidentally, an inner constrained containment is more effective in most cases,reducing the initial peak load without drastically reducing the SEA value.

As ore grades decline, waste rock to ore ratios increase and mines become progressively deeper mining operations face challenges in more complex scenarios. Today´s predominant means of material transport in hard-rock surface mines are conventional mining trucks however despite rationalisation efforts material transportation cost increased significantly over the last decades and currently reach up to 60% of overall mining. Thus, considerations and efforts to reduce overall mining costs, promise highest success when focusing on the development of more economic material transport methods. Semi-mobile in-pit crusher and conveyor (SMIPCC) systems represent a viable, safer and less fossil fuel dependent alternative however its viability is still highly argued as inadequate methods for the long term projection of system capacity leads to high uncertainty and consequently higher risk. Therefore, the objective of this thesis is to develop a structured method for the determination of In-pit crusher and conveyor SMIPCC system that incorporates the random behaviour of system elements and their interaction. The method is based on a structured time usage model specific to SMIPCC system supported by a stochastic simulation. The developed method is used in a case study based on a hypothetical mine environment to analyse the system behaviour with regards to time usage model component, system capacity, and cost as a function of truck quantity and stockpile capacity. Furthermore, a comparison between a conventional truck & shovel system and SMIPCC system is provided. Results show that the capacity of a SMIPCC system reaches an optimum in terms of cost per tonne, which is 24% (22 cents per tonne) lower than a truck and shovel system. In addition, the developed method is found to be effective in providing a significantly higher level of information, which can be used in the mining industry to accurately project the economic viability of implementing a SMIPCC system.

Edgewise crushing responses of composite aluminum honeycomb sandwich structures were predicted using finite element analysis (FEA) software LS-DYNA by modeling the honeycomb as a material with anisotropic properties. The goal of the project was to develop a process for modeling the sandwich structure to rapidly iterate possible solutions for a safer workstation train table. Current workstation tables are too rigid and may cause injury or death in a head-on collision. Experimental compression tests were used to calibrate the aluminum honeycomb core with material type 26 (MAT 26, honeycomb). A published composite tensile test was used to validate the use of material type 22 (MAT 22, composite damage) for laminates. Finally, a model was made to recreate the results of a published compression test of an aluminum honeycomb sandwich structure with aluminum sheet metal face sheets to confirm contact types. With each component of the model verified separately, three plain weave composite aluminum honeycomb sandwich structures were modeled, one with [0/90] composite sheets completely bonded to the core, one with [0/90] composite sheets partially bonded to the core, and one with [±45] composite sheets partially bonded to the core. The failure modes for each sandwich structure were previously shown through research and the elastic region of the response was checked for accuracy using a simple beam theory. The analysis suggests that incorporating unbonded zones into the sandwich structure will change the failure mode from general buckling to face wrinkling, which effectively lowers the failure strength while not sacrificing energy absorption throughout loading. The analysis also indicates that using an angled ply orientation will lower the initial stiffness and the failure load. Future work is recommended such as performing compression tests with composite aluminum honeycomb sandwich structures and integrating delamination failure modes into the model using cohesive elements.

No description available.

The diploma thesis deals with using of recycled aggregate of concrete for base layers of pavement. The work is divided into practical and theoretical part. The theoretical part deals with basic concepts of construction and demolition waste, production, development and management of this waste in the Czech Republic. It also focuses on the principle of recycling and the use of recycled concrete in the Czech Republic and abroad. The practical part of the thesis deals with laboratory testing and assessment of recycled aggregates in bound, unbound and grouted courses layers of the base layers of roads.

In vielen Bereichen der Tagebautechnik spielt die Zerkleinerung von Material/ -strömen eine wesentliche Rolle, wobei sich je nach Material verschiedene Anforderungen an das Brechersystem ergeben. In Folge dessen werden Brecher auftragsspezifisch, meist für einen speziellen Gesteinstyp oder Einsatzort entwickelt oder modifiziert. Eine aussagekräftige Prognose der im Bruchprozess auftretenden Lasten auf den Brecher ist somit essentieller Bestandteil im Entwicklungsprozess. Ein viel versprechender Ansatz, um das Materialverhalten in der Lastprognose zu berücksichtigen, ist die numerische Simulation des Materialbruchverhaltens mit Hilfe der Diskreten-Elemente-Methode (DEM). Das Verhalten der sogenannten Partikel wird über Kontakt- und bond-Modelle beschrieben und soll das makroskopische Verhalten des jeweiligen Gesteins möglichst realitätsnah abbilden. Die Problematik ist, dass in SimulationX® keine Module zur DEM-Simulation vorhanden sind und umgekehrt in der DEM-Simulationsumgebung LIGGGHTSG® (LAMMPS improved for general granular and granular heat transfer simulations) keine derartige Maschinensimulation möglich ist. Der Ausweg ist die Co-Simulation zweier unterschiedlicher Simulationsumgebungen durch die Nutzung des ,,Functional Mock-Up Interface“-Standards (FMI). Berechnungsergebnis sind die dynamischen Lasten auf den Brecher unter Berücksichtigung des Materialverhaltens. Somit können früher in der Brecherentwicklung Prognosen zu auftretenden Lasten getroffen und Einflussuntersuchungen von Maschinenkonfigurationen zur Effizienzsteigerungen durchgeführt werden, was zuvor auf Grund des Einzelanfertigungscharakters nicht möglich oder nicht wirtschaftlich war.

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2016-06-22T13:51:24Z No. of bitstreams: 0 / Made available in DSpace on 2016-06-22T13:51:24Z (GMT). No. of bitstreams: 0 / Tese (Doutorado em Tecnologia Nuclear) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP