Modelamento e simulação de impacto balístico em sistema cerâmica-metal

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Ciência e Engenharia de MateriaisNovos sistemas de proteção balística vêm sendo recentemente criados com base em materiais de alta tecnologia. Um dos objetivos da indústria do ramo é desenvolver sistemas defensivos mais leves, porém mais fortes, que possibilitem ao portador, veicular ou humano, uma maior mobilidade com um maior nível de segurança. Este trabalho, baseado no trabalho original de Al-Qureshi et al [1], estuda matematicamente o comportamento de uma proteção contra um impacto de projétil. O modelo empregado inclui um sistema de proteção em camadas de cerâmica e metal, e ainda descreve o comportamento do projétil e as propriedades de absorção de impacto do sistema. A literatura ainda mostra que a taxa de erosão e desaceleração do projétil são altamente dependentes dos parâmetros geométricos e estruturais do material da proteção. O fenômeno de impacto e penetração é descrito em diferentes estágios, apresentando características particulares entre tais. As equações apresentadas demonstram diferentes propriedades do sistema ao longo dos estágios. Este trabalho ainda apresenta uma simulação matemática realizada sobre o modelo desenvolvido e aprimorado em busca de propriedades otimizadas do material para estudos futuros. Dentre as propriedades investigadas citam-se a espessura das placas utilizadas, o perfil de deformação do material metálico, a densidade da cerâmica, dentre outras características relevantes para o fenômeno. A rotina computacional possibilitou a aplicação de diferentes parâmetros nas equações propostas. Como resultado, gráficos e superfícies foram geradas, o que possibilitou uma análise mais profunda do modelo e um maior entendimento do processo de fratura em materiais por impacto de alta velocidade. Estudos futuros utilizarão estes resultados e desenvolvimentos para a produção de uma proteção balística que será utilizada para um experimento prático

Tensão de ruptura verdadeira sob tração de fibras cerâmicas em feixes : experimentos e simulação

Fibras de materiais cerâmicos óxidos apresentam características peculiares de alta resistência mecânica e estabilidade química em ambientes de alta temperatura. Por conta disto, tais materiais podem ser empregados em sistemas de isolamento térmico bem como em compósitos de matriz cerâmica para aplicações aeroespaciais onde estabilidade estrutural é requerida. Tendo em vista isso, a compreensão do comportamento mecânico deste material é de grande interesse. Nesse trabalho, foi investigado por meio de experimentos e simulação o comportamento sob tração até a tensão verdadeira de ruptura de 2 tipos diferentes de fibras cerâmicas em feixes. As fibras cerâmicas utilizadas foram as comerciais Nextel 610 (alumina) e Nextel 720 (mulita), produzidas pela empresa 3M. Amostras foram submetidas a ensaios de tração utilizando corpos de prova com diferentes quantidades de fibras para a determinação de sua tensão verdadeira de ruptura. Para o cálculo desta, foi proposto um método baseado na detecção e classificação de sinais de ruptura em classes de carregamento. Os resultados experimentais obtidos revelaram um comportamento de aumento de mais de cinquenta por cento da tensão de ruptura verdadeira dos feixes de fibras com crescente quantidades de fibras. Em paralelo, simulações foram desenvolvidas e executas com o objetivo de determinar a tensão de ruptura verdadeira das fibras baseado nos parâmetros da distribuição de Weibull para a ruptura de fibras simples. Para isto, um novo sistema de posicionamento de fibras foi desenvolvido juntamente com um novo algoritmo de detecção de vizinhança para a implementação de modelos de compartilhamento de carga na simulação. Ainda, um novo modelo de compartilhamento de carga baseado no espalhamento do carregamento compartilhado foi proposto e aplicado no algoritmo de simulação. Por meio do método computacional, também se verificou uma crescente tensão de ruptura verdadeira dos feixes de fibras com a quantidade de fibras inicial do feixe nas mesmas proporções dos dados experimentais. No entanto, os modelos de compartilhamento de carga apresentaram resultados pouco diferentes, impedindo a determinação do modelo mais adequado para o estudo do fenômeno. Por fim, suposições foram feitas em relação ao desempenho dos modelos e algumas explanações dadas a fim de auxiliar a compreensão do fenômeno da variação da tensão de ruptura verdadeira dos feixes de fibras cerâmicas.Fibers of oxide ceramic materials have peculiar characteristics of high mechanical resistance and chemical stability in high temperature environments. Because of this, such materials can be used in thermal insulation systems as well as in ceramic matrix composites for aerospace applications where structural stability is required. In view of this, understanding the mechanical behavior of this material is of great interest. In this work, it was investigated through experiments and simulation the behavior under tension until the real breaking tension of 2 different types of ceramic fibers in bundles. The ceramic fibers used were the commercial Nextel 610 (alumina) and Nextel 720 (mullite), produced by the company 3M. Samples were subjected to tensile tests using specimens with different amounts of fibers to determine their true tensile strength. To calculate this, a method based on the detection and classification of rupture signals in loading classes was proposed. The experimental results obtained revealed an increase behavior of more than fifty percent of the true tensile strength of the fiber bundles with increasing amounts of fibers. In parallel, simulations were developed and performed with the objective of determining the true fiber breaking stress based on the Weibull distribution parameters for single fiber breaking. For this, a new fiber positioning system was developed together with a new neighborhood detection algorithm for the implementation of load sharing models in the simulation. In addition, a new load sharing model based on spreading the shared load was proposed and applied to the simulation algorithm. Through the computational method, there was also an increasing true tensile strength of the fiber bundles with the initial fiber quantity of the bundle in the same proportions as the experimental data. However, the load sharing models showed slightly different results, preventing the determination of the most appropriate model for the study of the phenomenon. Finally, assumptions were made in relation to the performance of the models and some explanations given in order to assist the understanding of the phenomenon of variation in the true rupture stress of the bundles of ceramic fibers

POPULARIZAÇÃO CIENTÍFICA E TECNOLÓGICA: EXPERIMENTOS DE FÍSICA ITINERANTES NO AMBIENTE ESCOLAR

O projeto Popularização Científica e Tecnológica é um projeto de extensão da Universidade do Extremo Sul Catarinense que busca levar até as escolas experimentos demonstrativos de física por meio de apresentações interativas. O projeto existe desde 2011 e surgiu da necessidade de tornar o ensino de física mais  atrativo e próximo da realidade vivencial, no que se refere à compreensão da natureza por meio dos estudantes. Para isto, experimentos são desenvolvidos com o objetivo de apresentar, explorar e compreender fenômenos físicos naturais dentro das diferentes áreas da física (mecânica, térmica, óptica, elétrica, ondulatória e moderna). Os experimentos são apresentados em um formato de espetáculo, de forma a inspirar os estudantes que participam da apresentação. O projeto já atendeu 59 escolas até o momento e, durante a pandemia, realizou 4 apresentações por meio de transmissão via internet feita do laboratório de física experimental da Unesc (LaFiEx). Como resultado, percebe-se um aumento no interesse dos alunos das escolas atendidas por ciência e tecnologia e, ainda, uma conscientização de professores das próprias escolas em relação à importância da utilização de recursos experimentais para aprimoramento do processo de ensino-aprendizagem

The impact of air pollution on the rate of degradation of the fortress of Florianópolis Island, Brazil

The study of the prevalence of agglomerated nanoparticles (ANPs) containing potentially hazardous elements (PHEs) in the atmosphere is an emerging field of research. As such, the development of effective analytical procedures for the documentation of ANPs in air dust is vital for the evaluation of human health consequences. X-ray powder diffraction (XRD), Raman spectroscopy (RS), Mossbauer spectroscopy (MS) and advanced microscopy (AM) analyses of levels of pollutant concentration have been completed for many years in buildings worldwide. The chemical and mineralogical features of the Fortress of Nossa Senhora da Conceição de Araçatuba in the Brazilian state of Santa Catarina were utilized to catalog the geologic makeup of the structure's raw materials. Analyses of diverse categories of historical building were developed and performed to show the incidence of normal and anthropogenic compounds with PHEs. These geochemical effects and the subsequent fate and transport of nanoparticulate and colloidal (1–1000 nm) compounds in the atmosphere have remained a focus of study for many years. However, the data published in the scientific literature is nowhere near adequate to generate an exhaustive standard of the performance, fate, and transport of natural and anthropogenic ANPs in the atmosphere. Studies to date do provide a preliminary argument for the human health risk calculations from historical buildings due to ANPs. Thus, the geochemical makeup of ANPs and their position in collected nanomineral–organic accumulations may offer some insight into their source. Our ability to detect such ANPs may decrease over time due to the tendency of historical buildings to accrete sludge over the years. The occurrence of PHEs in atmospheric ANPs has not formerly been recognized on the island environment examined in this study. However, it has been shown that it presents a clear and present danger to the preservation of historical monuments

Nanomineralogy of mortars and ceramics from the Forum of Caesar and Nerva (Rome, Italy): the protagonist of black crusts produced on historic buildings

The recent focus of the impacts of atmospheric pollution on effective conservation methods for historic structures of great cultural heritage has been shown to be of critical importance for preservation. This work focuses on medieval Roman mortars and ceramics from the historic Forum of Caesar and Nerva, in Rome, Italy, and analyzes the urgency of repair of defects in rendered façades based on the inspection of surfaces where defects were detected, defining a methodology to predict the repair urgency of defects and building elements. X-ray spectroscopy (EDS), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), and X-ray powder diffraction (XRD) analyses are well equipped to study mineralogy, ultra-fine particles, and nanoparticles (NPs, minerals and amorphous phases) that are present in medieval Roman ruins. Applied analysis of ruin-derived mortar and ceramics detected the presence of materials, primarily constituted of quartz, alumino-silicates, Fe-hydr/oxides, portions of amorphous phases, calcareous minerals, pyroxene, and carbonaceous materials. The Forum of Caesar and Nerva are two of the greatest remaining symbols of historic Roman construction. Many compounds recognized by XRD can be revealed by advanced microscopies and vice versa. The incidence of NPs containing potentially toxic elements (PTEs), and numerous carbonaceous complexes linked with building material alterations due to moisture and atmospheric contamination were also discovered. This study assesses the philosophies of preservation and culture, while considering the exhaust emitted by vehicular traffic in order to propose a justifiable and effective method to best conserve historic Roman structures located in high traffic areas

Atmospheric nanocompounds on lanzarote island: vehicular exhaust and igneous geologic formation interactions

Atmosphere contamination management is one of the most important features in pollution risk management. The worldwide rise in tourism increases apprehension about its probable destructive conservation influence on various aspects of global conservation. One of the principal dangers increased by tourism-based modes of travel are nanoparticles (NPs) containing potentially hazardous elements (PHEs) contamination. One example of this is island destination of Lanzarote, in Spain's Canary Islands in which we examined contamination of the local atmosphere, water and soil. Important NPs containing PHEs, (e.g. arsenic, chromium, lead, and mercury), were found in this locale. It is reasonable to assume that this pollution poses an increased environmental danger to the local biome(s). Modes of transport (i.e. by car, airplane, bus) were shown to be an important contributor to this localized contamination as demonstrated by particulate matter (PM) readings collected near the island's airport. If no measures are taken to reduce vehicle and aircraft traffic, the tendency is to increase environmental degradation will continue unabated. As this particular area of Lanzarote is also one of wine production, increased pollution has the potential for negative impacts on the region's economy

Nanoparticles as vectors of other contaminants in estuarine suspended sediments: natural and real conditions

Studding the behaviour and danger of nanoparticles (NPs, minerals and amorphous phases) in the estuarine ecosystem is presently incomplete by the lack of measureable description of NPs in the ecological conditions, such as suspended-sediments (SS). In the last years, several works have revealed the toxic consequences of ultra-fine and nanoparticulate compounds on diverse systems, raising apprehensions over the nanocontaminants behaviour and destiny in the numerous ecological partitions. The general objective of the manuscript is to explain the geochemical conditions of the LES (Laguna estuarine system, southern Brazil) suspended sediments covering an area around the main South American coal plant, enhancing the creation of future public policies for environmental recovery projects. Subsequently the discharge of nanoparticles and toxic element (TE) in the ecosystem, NPs react with several constituents of the nature and suffers active alteration progressions. Contamination coming from engineering actions, wastewater, are something identifiable, however when these contaminations are accompanied by other contamination sources (e.g. mining and farming) the work gets defaulted. By combining material about the concentration of TE contaminants and NPs occurrences, this work offers novel visions into contaminant contact and the possible effects of such exposure on estuarine systems in Brazil. The results presented here will be useful for different areas of estuaries around the world

Environmental aspects of the depreciation of the culturally significant Wall of Cartagena de Indias – Colombia

Among the diverse archeological relics of the past, the Cartagena de Indias Wall is one of the greatest representations of European cultural architecture in South America. To assess the implication of contamination on the depreciation of the culturally significant Wall of Cartagena de Indias - Colombia, a detailed, multi-analytical approach was conducted on components of the wall. Accumulated ultra-fine particles (UFPs) and superficial nano-particles (NPs) containing hazardous elements (HEs) on the wall were identified in an attempt to understand whether atmospheric pollution is hastening the depreciation of the structure itself. Mortar which at one point held the stones together is now weak and has fallen away in places. Irreparable damage is being done by salt spray, acid rain and the site's tropical humid climate. Several HEs and organic compounds found within the local environment are also contributing to the gradual deterioration of the construction. In this study, advanced microscopy analyses have been applied to understand the properties of UFPs and NPs deposited onto the wall's weathered external walls through exposure to atmospheric pollution. Several materials identified by X-Ray Diffraction (XRD) can be detected using high-resolution transmission electron microscopy (HR-TEM) and field emission scanning electron microscope (FE-SEM). The presence of anglesite, gypsum, hematite containing HEs, and several organic compounds modified due to moisture and contamination was found. Black crusts located on the structure could potentially serve as a source of HEs pollution and a probable hazard to not only to the ecosystem but also to human health

Nanoparticles as vectors of other contaminants in estuarine suspended sediments: Natural and real conditions

Studding the behaviour and danger of nanoparticles (NPs, minerals and amorphous phases) in the estuarine ecosystem is presently incomplete by the lack of measureable description of NPs in the ecological conditions, such as suspended-sediments (SS). In the last years, several works have revealed the toxic consequences of ultra-fine and nanoparticulate compounds on diverse systems, raising apprehensions over the nanocontaminants behaviour and destiny in the numerous ecological partitions. The general objective of the manuscript is to explain the geochemical conditions of the LES (Laguna estuarine system, southern Brazil) suspended sediments covering an area around the main South American coal plant, enhancing the creation of future public policies for environmental recovery projects. Subsequently the discharge of nanoparticles and toxic element (TE) in the ecosystem, NPs react with several constituents of the nature and suffers active alteration progressions. Contamination coming from engineering actions, wastewater, are something identifiable, however when these contaminations are accompanied by other contamination sources (e.g. mining and farming) the work gets defaulted. By combining material about the concentration of TE contaminants and NPs occurrences, this work offers novel visions into contaminant contact and the possible effects of such exposure on estuarine systems in Brazil. The results presented here will be useful for different areas of estuaries around the world

Identification of hazardous nanoparticles present in the Caribbean Sea for the allocation of future preservation projects

The deposition of remaining nanoparticles in the Caribbean Sea generates the formation of potentially dangerous elements, which influence at the imbalance of ecosystems. The detection of nanoparticles is not simple and the use of conventional methods is difficult application, which is why we highlight the immediacy and importance of this research for the areas of marine biology, urbanism, engineering and geosciences, applied in the Caribbean Sea. The general objective of this study is to evaluate the use of advanced methods for the determination of toxic nanoparticles, which can directly affect the development of marine organisms in the aquatic ecosystem in waters of the Caribbean Sea, favoring the construction of future international public policies with the elaboration of projects capable of mitigating these levels of contamination. The morphology and structure of nanoparticles were analyzed by emission scanning electron microscope with a high-resolution electron microscope. The nanoparticles smaller than 97 nm were identified in different proportions. The morphological analyses indicated nanoparticles' presence in the form of nanotubes, nanospheres, and nanofibers, which were shown in an agglomerated form. The presence of potentially hazardous elements, such as As, Cd, Pb, Mg, Ni and V were verified. In addition, the presence of asbestos in the form of minerals was confirmed, and that of titanium dioxide was found in large quantities. The results provide new data and emphasize the possible consequences to the in the Caribbean Sea, with the identification of dangerous elements (As, Cb, Pb, Hg, Ni and V), harmful to the marine ecosystem. Therefore, there is a need for strict control to reduce contamination of the Caribbean Sea and avoid risks to the ecosystem and public health, through suggestions of international public policies, through constant monitoring and the application of environmental recovery projects in this marine estuary