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Authors
Abstract(s)
O trabalho desenvolvido no âmbito do Instituto Politécnico de Bragança engloba
a caracterização do comportamento superelástico de uma liga com memória de forma
(LMF) composta em sua maioria por Níquel e Titânio (NiTi). Através de estudos
experimentais e calibração de modelos numéricos pretende-se simular o comportamento
ímpar das ligas, com o intuito de possibilitar o desenvolvimento de dispositivos capazes
de atenuar vibrações indesejadas de altas amplitudes, como em fenômenos de sismos.
Uma LMF possui duas propriedades que destacam a sua categoria dos demais materiais
inteligentes, o efeito memória de forma e a superelasticidade. O primeiro consiste na
capacidade do material em retornar a uma forma pré-definida após sofrer uma deformação
aparentemente plástica, enquanto que a segunda indica a formação de um laço de histerese
no diagrama tensão-deformação sendo um mecânismo de dissipação de energia.
Estudos realizados utilizando o software Ansys® APDL™ apresentaram o
comportamento de um provete cilíndrico feito com a liga de NiTi em uma condição quásiestática
e dinâmica, na forma de carregamentos cíclicos, onde um algoritmo foi
implementado no software Matlab® com o intuito de permitir a simulação deste último
comportamento. Essa aproximação utiliza equações para atualizar as propriedades
características do provete conforme ocorre a evolução temporal da simulação.
Ensaios de tração foram realizados, sob a forma de ruptura assim como cíclicos,
com o objetivo de obter as propriedades características dos materiais disponíveis e
permitir a calibração dos modelos numéricos.
De forma a complementar a caracterização do material realizou-se um ensaio
dinâmico para obtenção da frequência de vibração de um provete utilizando técnicas de
processamento de imagem resultando na primeira frequência natural da liga. A
comprovação do resultado obtido deu-se por uma análise modal utilizando o software
SolidWorks® apresentando valores compatíveis. A partir dos estudos numéricos e experimentais realizados, conclui-se que o
objetivo de caracterizar propriedades básicas do material foi bem sucedida, uma vez que
as técnicas experimentais foram adaptadas de forma a permitir a calibração de modelos
numéricos com o intuito de que a simulação de futuras aplicações possam permitir uma
implementação mais rápida da tecnologia.
The work developed within the scope of the Polytechnic Institute of Braganza encompasses the characterization of the superelastic behavior of a shape memory alloy (SMA) composed mostly of nickel and titanium. Through experimental studies and calibration of numerical models, we intend to simulate the unique behavior of the alloys in order to enable the development of devices able to mitigate unwanted vibrations of high amplitudes, as in earthquakes. A SMA has two properties that highlight its category of other intelligent materials, the shape memory effect and the superelasticity. The first is the ability of the material to return to a predefined shape after undergoing an apparently plastic deformation, while the second indicates the formation of a hysteresis loop in the stress-strain diagram being a mechanism of energy dissipation. Studies performed using Ansys® APDL™ software presented the behavior of a cylindrical specimen made with the NiTi alloy in a quasi-static and dynamic condition, in the form of cyclic loading, where an algorithm was implemented in Matlab® software in order to simulation of the latter behavior. This approach uses equations to update the characteristic properties of the specimen as the time evolution of the simulation occurs. Tensile tests were performed in the form of rupture as well as cyclic, in order to obtain the characteristic properties of the available materials and to allow the calibration of the numerical models. In order to complement the characterization of the material a dynamic test was performed to obtain the vibration frequency of a specimen using image processing techniques resulting in the first natural frequency of the alloy. The proof of the obtained result was given by a modal analysis using SolidWorks software presenting compatible values. From the numerical and experimental studies, it was concluded that the objective of characterizing basic properties of the material was successful, since the experimental techniques were adapted in order to allow the calibration of numerical models with the intention that the simulation of future applications can enable faster implementation of the technology.
The work developed within the scope of the Polytechnic Institute of Braganza encompasses the characterization of the superelastic behavior of a shape memory alloy (SMA) composed mostly of nickel and titanium. Through experimental studies and calibration of numerical models, we intend to simulate the unique behavior of the alloys in order to enable the development of devices able to mitigate unwanted vibrations of high amplitudes, as in earthquakes. A SMA has two properties that highlight its category of other intelligent materials, the shape memory effect and the superelasticity. The first is the ability of the material to return to a predefined shape after undergoing an apparently plastic deformation, while the second indicates the formation of a hysteresis loop in the stress-strain diagram being a mechanism of energy dissipation. Studies performed using Ansys® APDL™ software presented the behavior of a cylindrical specimen made with the NiTi alloy in a quasi-static and dynamic condition, in the form of cyclic loading, where an algorithm was implemented in Matlab® software in order to simulation of the latter behavior. This approach uses equations to update the characteristic properties of the specimen as the time evolution of the simulation occurs. Tensile tests were performed in the form of rupture as well as cyclic, in order to obtain the characteristic properties of the available materials and to allow the calibration of the numerical models. In order to complement the characterization of the material a dynamic test was performed to obtain the vibration frequency of a specimen using image processing techniques resulting in the first natural frequency of the alloy. The proof of the obtained result was given by a modal analysis using SolidWorks software presenting compatible values. From the numerical and experimental studies, it was concluded that the objective of characterizing basic properties of the material was successful, since the experimental techniques were adapted in order to allow the calibration of numerical models with the intention that the simulation of future applications can enable faster implementation of the technology.
Description
Keywords
Ligas com memória de forma Estudo numérico-experimental Caracterização do comportamento do material