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Advisor(s)
Abstract(s)
Nestas últimas décadas tem-se assistido a um aumento exponencial do número de
materiais no mercado e esta tendência será para continuar, face às cada vez maiores
exigências dos consumidores. É necessário criar e desenvolver materiais que permitam
corresponder em termos de características específicas às necessidades da vida
moderna, aos preços mais baixos. Este facto leva a uma busca incessante por parte dos
cientistas e estudiosos que se dedicam ao estudo dos materiais e das suas propriedades
e à relação entre a sua estrutura em escalas atômicas ou moleculares com suas
características macroscópicas, incorporando elementos da física e da química como as
formas de caracterização e processamento.
Atualmente é praticamente impossível imaginar o mundo como o conhecemos, sem o
uso dos plásticos e desde a sua descoberta, que estes se tem vindo a aperfeiçoar e a
desenvolver sendo aplicado com grande sucesso nas mais diversas áreas, substituindo
materiais como o vidro e mesmo os próprios metais. A baixa densidade, a facilidade de
processamento e o seu baixo custo, são os principais fatores que incentivam a utilização
de alguns plásticos ou resinas, sendo usados em larga escala. Existe atualmente no
mercado uma grande variedade de plásticos, com características e propriedades muito
diferentes e para todos os tipos de aplicação.
Este trabalho tem como objetivo caracterizar vários materiais utilizados em hélices de
motoventiladores, avaliar as temperaturas e o ruído no seu funcionamento de forma a
responder a uma solicitação da empresa SKK, uma vez que esta não dispõe de
informação suficiente para poder garantir a aplicabilidade real dessas hélices. Nesse sentido, e uma vez que o tipo de material polimérico utilizado nas hélices não é
conhecido, houve necessidade de realizar uma série ensaios mecânicos e físico-químicos
em alguns materiais, de modo a ser possível proceder-se à sua caracterização,
identificando as suas principais propriedades e características.
Os materiais em estudo passaram por ensaios de tração, dureza, queima e densidade,
sendo também efetuadas medições de rugosidades nas suas superfícies. O ponto de
amolecimento do material foi outra propriedade que se procurou definir através do
ensaio de VICAT. Terminados estes ensaios, os valores obtidos foram registados, para
que em seguida se procedesse à sua identificação, através da comparação destes valores
calculados com os valores padrão de cada material. Foram também analisadas as
temperaturas a que estes materiais estão sujeitos no seu funcionamento, comparandose
estes valores com os resultados obtidos no ensaio de VICAT.
Por fim, foram analisados os níveis de ruido apresentados pelos diferentes materiais,
tentando estabelecer-se uma relação entre os referidos níveis de ruido e a sua
rugosidade.
Embora os ensaios não sejam conclusivos, é possível dizer que qualquer um dos
materiais utilizados é apto para a função a que se destina, pois os esforços envolvidos
nas hélices são muito baixos e as temperaturas reais de funcionamento são
significativamente inferiores às admissíveis para os materiais em causa. Ainda assim, e
considerando que o objetivo é a possibilidade de substituir as hélices de alumínio por
hélices de plástico, em termos de resistência mecânica o material que mais se destaca é
sem dúvida o alumínio, com larga vantagem, chegando a um valor de tensão máxima de
171 MPa, valor bastante acima do que é requerido, visto os baixos esforços a que as
hélices estão sujeitas. Os valores apresentados pelos materiais plásticos são bastante
menores, contudo suficientes para a sua função, sendo o material P o que possui o valor
da tensão superior, atingindo os 26 MPa.
Em termos de análise de temperatura, todos os materiais apresentam valores
semelhantes, rondando entre os 45°C e os 52°C sensivelmente. Estes valores são
bastante baixos, comparativamente aos valores dos seus pontos de fusão que variam entre os 94°C e os 112°C, logo, neste campo, qualquer dos polímeros é capaz de cumprir
com a sua função.
No que diz respeito ao ruído, verifica-se novamente uma semelhança entre todos os
materiais, atingindo valores máximos de 50 dB, sendo que entre eles, estes valores
apenas variam 1 ou 2 dB.
Em relação ao rendimento elétrico, ou seja, o rácio entre a potência útil e a potência
consumida pelo equipamento, a hélice que apresenta melhores resultados é a do
material P, muito embora, no motor de comutação eletrónica (ECM), para caudais
elevados, este fique um pouco abaixo dos outros. Outro parâmetro importante a ter em
consideração, é o rácio entre as rotações efetuadas pela hélice e o caudal atingido,
sendo que, que neste caso o material P é novamente o que apresenta melhores
resultados, conseguindo para um mesmo caudal trabalhar a menos rotações que os
restantes.
In the last few decades, there has been an exponential increase in the number of materials on the market and this trend is to continue, given the increasing demands of consumers. It must create and develop materials that allow to match in terms of specific characteristics to the needs of modern life, at the lowest prices. This leads to a relentless pursuit for new materials, by scientists and scholars dedicated to the study of materials and their properties and the relationship between their structure in atomic or molecular scales with their macroscopic characteristics, incorporating elements of physics and chemistry as the forms of characterization and processing. Currently, it is virtually impossible to imagine the world as we know it without the use of plastics and since their discovery have been improved and developed, being applied with great success in several areas, replacing materials such as glass and even the metals themselves. The low density, ease of processing and its low cost are the main factors that encourage the use of some plastics or resins being used on a large scale. There is currently on the market a wide range of plastics with different properties and characteristics and for all types of applications. This work carried out a series of mechanical and physicochemical tests at some materials in order to be possible to do his characterization, identifying its main properties and characteristics. The materials under study were submitted to a several tests, like the tensile test, the hardness test, burning and density, roughness measurements are also made on their surfaces. The softening point of the material was another property to be defined, through the VICAT test. Completed these tests, the values were recorded, to make the identification by comparing these calculated values with the default values for each material. The temperatures that these materials are subject in their operation were also analysed, comparing these values with the results obtained in the VICAT test. Finally, the noise levels presented by the different materials were analysed, in order to establish a relationship between these levels of noise and its roughness. Although the tests are non-conclusive, it is possible to say that any of the materials used is suitable for the function for which it is planned, because the efforts involved in the propellers are very low and the actual operating temperatures are significantly lower than those eligible for the materials in cause. Still, considering that the goal is the possibility of replacing aluminium propellers for plastic propellers in terms of mechanical strength, the material that stands out most is undoubtedly the aluminium, by a wide margin, reaching a voltage value maximum of 171 MPa, well above what is required, since the blades are subjected at low stresses. The values presented at the plastic materials are much smaller, but yet sufficient for its function, and the P material, is the one which has the highest value, reaching 26 MPa. In terms of temperature analysis, all materials have similar values, ranging between 45 ° C and 52 ° C. These values are very low compared with the values of their melting points ranging from 94 ° C to 112 ° C, so in this field, any of the polymers is able to fulfil its function. With regard to noise, it appears again a similarity between all materials, reaching maximum values of 50 dB, being that between them, these values vary only 1 or 2 dB. Regarding electrical performance, this means, the ratio between the power output and the power consumed by the machine, the propeller that shows best results is the P material, although in the electronic switching motor (ECM), for the high flow rates, it becomes worst comparing with the others. Another important parameter to consider, is the ratio between the revolutions made by propeller and you’re reached flow, being that, in this case, P material, it is again the material which gets the best results, achieving, less rotations, for a same air flow quantity.
In the last few decades, there has been an exponential increase in the number of materials on the market and this trend is to continue, given the increasing demands of consumers. It must create and develop materials that allow to match in terms of specific characteristics to the needs of modern life, at the lowest prices. This leads to a relentless pursuit for new materials, by scientists and scholars dedicated to the study of materials and their properties and the relationship between their structure in atomic or molecular scales with their macroscopic characteristics, incorporating elements of physics and chemistry as the forms of characterization and processing. Currently, it is virtually impossible to imagine the world as we know it without the use of plastics and since their discovery have been improved and developed, being applied with great success in several areas, replacing materials such as glass and even the metals themselves. The low density, ease of processing and its low cost are the main factors that encourage the use of some plastics or resins being used on a large scale. There is currently on the market a wide range of plastics with different properties and characteristics and for all types of applications. This work carried out a series of mechanical and physicochemical tests at some materials in order to be possible to do his characterization, identifying its main properties and characteristics. The materials under study were submitted to a several tests, like the tensile test, the hardness test, burning and density, roughness measurements are also made on their surfaces. The softening point of the material was another property to be defined, through the VICAT test. Completed these tests, the values were recorded, to make the identification by comparing these calculated values with the default values for each material. The temperatures that these materials are subject in their operation were also analysed, comparing these values with the results obtained in the VICAT test. Finally, the noise levels presented by the different materials were analysed, in order to establish a relationship between these levels of noise and its roughness. Although the tests are non-conclusive, it is possible to say that any of the materials used is suitable for the function for which it is planned, because the efforts involved in the propellers are very low and the actual operating temperatures are significantly lower than those eligible for the materials in cause. Still, considering that the goal is the possibility of replacing aluminium propellers for plastic propellers in terms of mechanical strength, the material that stands out most is undoubtedly the aluminium, by a wide margin, reaching a voltage value maximum of 171 MPa, well above what is required, since the blades are subjected at low stresses. The values presented at the plastic materials are much smaller, but yet sufficient for its function, and the P material, is the one which has the highest value, reaching 26 MPa. In terms of temperature analysis, all materials have similar values, ranging between 45 ° C and 52 ° C. These values are very low compared with the values of their melting points ranging from 94 ° C to 112 ° C, so in this field, any of the polymers is able to fulfil its function. With regard to noise, it appears again a similarity between all materials, reaching maximum values of 50 dB, being that between them, these values vary only 1 or 2 dB. Regarding electrical performance, this means, the ratio between the power output and the power consumed by the machine, the propeller that shows best results is the P material, although in the electronic switching motor (ECM), for the high flow rates, it becomes worst comparing with the others. Another important parameter to consider, is the ratio between the revolutions made by propeller and you’re reached flow, being that, in this case, P material, it is again the material which gets the best results, achieving, less rotations, for a same air flow quantity.
Description
Keywords
Caracterização de materiais Ensaios experimentais Propriedades dos materiais Material characteristics Experimental tests Material properties