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Advisor(s)
Abstract(s)
As ligas com memória tais como a liga Ni-Ti e Ni-Ti-X revelam excelentes características
de resistência à corrosão em meio aquático e conseguem gerar forças superiores quando
comparados com atuadores de natureza diferente mas de dimensões idênticas. Os arames
destas ligas, quando devidamente educados, permitem um comportamento que em muito se
assemelha ao comportamento de um músculo biológico.
Entre muitas áreas de pesquisa, a aplicabilidade de atuadores de ligas com memória de
forma para propulsão de veículos subaquáticos autónomos (AUV’s) tem sido discutida de forma
ativa nas últimas décadas.
Desta forma este trabalho pretende ser mais um contributo para esse estudo através de
ensaios de molas de Ni-Ti, construção de um protótipo de uma estrutura de barbatana e
análise do seu comportamento.
O trabalho descreve os ensaios termomecânicos realizados para determinar as
características de molas de Ni-Ti de 8 espiras com 5 mm de diâmetro e arame de 0,8 mm de
diâmetro. Consistiu ainda na conceção de uma estrutura biomimética de uma barbatana caudal
de um peixe com 3 segmentos independentes com recurso a uma “coluna vertebral” em forma
de mola. A indução de alteração da forma da estrutura foi permitida pela colocação das molas
de Ni-Ti nas” vértebras”, quatro por segmento e aquecidos aos pares de forma antagónica e
arrefecimento realizado por convecção forçada.
Os resultados obtidos mostraram o desenvolvimento de força elevada e sem emissão de
ruídos, frequência de oscilação da barbatana inferior ao necessário (com ar como meio de
permuta térmica) e consumos energéticos muito elevados.
Memory alloys such as Ni-Ti and Ni-Ti-X show excellent characteristics of corrosion resistance in water and can generate higher forces compared with actuators of different nature with equal dimensions and mass. The wires of these alloys, when properly educated, allow a behavior very similar to the behavior of a biological muscle. One of the many areas of research, the applicability of actuators with shape memory alloys dedicated to propulsion of autonomous underwater vehicles (AUV's) has been actively discussed in the recent decades. Thus, this work aims to be a contribution to this study by testing springs Ni-Ti, building a prototype of a fin structure and analysis of their behavior. The paper describes the thermo mechanical tests conducted to determine the characteristics of Ni-Ti springs. It was also conducted a construction of a prototype of a biomimetic structure of a tail fin of a fish with three independent segments using a central shaped spring "spine". The induced change in shape of the structure was allowed by placing the Ni-Ti springs on "vertebrae," 2 pairs per segments heated antagonistically. The cooling of the Ni-Ti is perform by 3 computer fans. The results show the development of high strength and no noise emission, the oscillation frequency of the fin below the requirements (with air as the thermal transfer medium) and very high energy consumption.
Memory alloys such as Ni-Ti and Ni-Ti-X show excellent characteristics of corrosion resistance in water and can generate higher forces compared with actuators of different nature with equal dimensions and mass. The wires of these alloys, when properly educated, allow a behavior very similar to the behavior of a biological muscle. One of the many areas of research, the applicability of actuators with shape memory alloys dedicated to propulsion of autonomous underwater vehicles (AUV's) has been actively discussed in the recent decades. Thus, this work aims to be a contribution to this study by testing springs Ni-Ti, building a prototype of a fin structure and analysis of their behavior. The paper describes the thermo mechanical tests conducted to determine the characteristics of Ni-Ti springs. It was also conducted a construction of a prototype of a biomimetic structure of a tail fin of a fish with three independent segments using a central shaped spring "spine". The induced change in shape of the structure was allowed by placing the Ni-Ti springs on "vertebrae," 2 pairs per segments heated antagonistically. The cooling of the Ni-Ti is perform by 3 computer fans. The results show the development of high strength and no noise emission, the oscillation frequency of the fin below the requirements (with air as the thermal transfer medium) and very high energy consumption.
Description
Keywords
Ligas com memória de forma; protótipo de sistema de propulsão; Ni-Ti; ensaios de tração. shape memory alloys; prototype propulsion system, Ni-Ti, tensile tests.