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Abstract(s)
A presente dissertação apresenta uma abordagem ao tema FluĂȘncia, com um desenvolvimento
geral para quatro materiais: madeira, alumĂnio, betĂŁo e aço. No entanto, particularizou-se este
estudo apenas para dois destes materiais, a madeira e o alumĂnio.
A madeira Ă© um material viscoelĂĄstico, logo fortemente influenciado quando submetido a uma
ação constante (FluĂȘncia) sendo agravada com alteraçÔes do teor em ĂĄgua.
Iniciou-se o estudo, com uma introdução aos objetivos principais e a revisão teórica do
conhecimento da propriedade mecĂąnica (FluĂȘncia). Efetuou-se o estudo inicial para os quatro
materiais indicados.
Posteriormente, fez-se avaliação do efeito mecùnico sortivo durante 60 dias com sete ciclos, em
provetes de dimensÔes 20 x 20 x 400 mm3 (escala 1:10) de madeira de Eucalyptus globulus Labill.
Recorrendo ao levantamento de um conjunto de modelos numéricos, procedeu-se ao ajuste e
extrapolação do comportamento, em FluĂȘncia, para distintos perĂodos de tempo (1, 10 e 50
anos). Os resultados obtidos demonstraram que a madeira de Eucalipto nĂŁo apresenta um limite
no seu comportamento em FluĂȘncia, logo instĂĄvel para os 60 dias de duração de ensaio.
Os diferentes modelos de FluĂȘncia (x6) apresentaram uma variabilidade crescente de resultados,
de acordo com o aumento de extrapolação dos resultados. Para a espécie de madeira de
Eucalipto constatou-se ainda, que o ajuste e extrapolação de deformação para 50 anos
ultrapassaram os valores sugeridos pelo EurocĂłdigo 5. A Ășltima parte deste trabalho, incidiu sobre
o desenvolvimento da metodologia do ensaio em flexĂŁo de 3 provetes de alumĂnio similares, cujas
dimensÔes eram de 20 x 20 x 400mm3. O objetivo desta metodologia foi avaliar o seu
comportamento em FluĂȘncia. Numa primeira fase, foi aplicada uma carga contante de 160 kN. E
numa segunda fase, foi aplicada o dobro dessa carga sujeita adicionalmente a uma temperatura
bastante superior Ă temperatura ambiente (a rondar os 50 oC).
Conclusivamente verificou-se que o alumĂnio nĂŁo apresenta deformação por FluĂȘncia, para as
condiçÔes de ensaio apresentadas.
The following dissertation presents an approach to the Creep subject with a general development towards four materials: wood, aluminum, concrete and steel, but with a close approach to wood and aluminum. Wood is a viscoelastic material, therefore it is highly influenced when submitted to a constant action (Creep), which can aggravate with the increase of water content. This study started with an introduction to the main objectives and theoretical knowledge of the mechanical properties of the four materials when subjected to the action Creep. an evaluation was performed to the mechanical sortive effect, during sixty days, with seven cycles, using 20 x 20 x 400 mm3 samples (scale 1:10) of Eucalyptus Globulus Labill wood species. Using six numeric models, it was carried out an adjustment and extrapolation to the behavior while submitted to the action Creep in different time periods (1, 10 and 50 years). The results allowed to conclude that Eucalyptus wood shows a limitless creep behavior, therefore unstable to the sixty days duration test. The different modules of creep (x6) show different results, meaning that the variation of the extrapolated results increases as the time increases. It was further found that the adjustment and extrapolation of creep for fifty years exceed the values suggested by Eurocode 5. The last part of this work focused on the development of the bending test methodology of three similar aluminum samples (20 x 20 x 400 mm3).The objective of this methodology was to evaluate the bending behavior. On a first stage 16Kg constant weight was applied. In a second stage, double the weight with the addition of increased temperature far superior to the ambient temperature (rounding the 50 o C). As conclusion, it was verified that aluminum doesnât react to creep, to the test conditions mentioned before and it hardly shows signs of creep to the normal ambient temperatures, as well as full-scale dimensions.
The following dissertation presents an approach to the Creep subject with a general development towards four materials: wood, aluminum, concrete and steel, but with a close approach to wood and aluminum. Wood is a viscoelastic material, therefore it is highly influenced when submitted to a constant action (Creep), which can aggravate with the increase of water content. This study started with an introduction to the main objectives and theoretical knowledge of the mechanical properties of the four materials when subjected to the action Creep. an evaluation was performed to the mechanical sortive effect, during sixty days, with seven cycles, using 20 x 20 x 400 mm3 samples (scale 1:10) of Eucalyptus Globulus Labill wood species. Using six numeric models, it was carried out an adjustment and extrapolation to the behavior while submitted to the action Creep in different time periods (1, 10 and 50 years). The results allowed to conclude that Eucalyptus wood shows a limitless creep behavior, therefore unstable to the sixty days duration test. The different modules of creep (x6) show different results, meaning that the variation of the extrapolated results increases as the time increases. It was further found that the adjustment and extrapolation of creep for fifty years exceed the values suggested by Eurocode 5. The last part of this work focused on the development of the bending test methodology of three similar aluminum samples (20 x 20 x 400 mm3).The objective of this methodology was to evaluate the bending behavior. On a first stage 16Kg constant weight was applied. In a second stage, double the weight with the addition of increased temperature far superior to the ambient temperature (rounding the 50 o C). As conclusion, it was verified that aluminum doesnât react to creep, to the test conditions mentioned before and it hardly shows signs of creep to the normal ambient temperatures, as well as full-scale dimensions.
Description
Keywords
MecĂąnico sortivo Limite de FluĂȘncia Creep limit Sorptive mechanical Creep