Estudo da aplicação da liga NiTi com efeito memória de forma em atuadores de aeronaves

Abstract

This work describes a computational study of the application of shape memory alloy wires (SMA), NiTi, as aircraft actuators, specifically to move one of the aircraft control surfaces, the flap. The computational study aimed to build a model of the actuator. The shape memory alloys are materials that have a peculiar thermo mechanical behavior, as they have the property to recover its original shape after undergoing large mechanical deformation. This property is related to the phase transformation, between austenite and martensite phases, which occurs in the alloy. For this reason the alloy has nonlinear constitutive behavior, making it necessary to use a constitutive model developed for this material. The constitutive model was implemented as a UMAT subroutine so that it can be used together with finite element program ABAQUS. The UMAT subroutine used in this work is the SMA_UM, implementing three different constitutive models developed for Shape Memory Alloys. To evaluate the response obtained by the subroutine was made necessary their validation by comparing the result of the tensile test with simulated by ABAQUS program. In addition to validating the subroutine, these simulations were analyzed to assess which of the constitutive models was the most suitable for use in other stages of the project. From the constitutive model defined as the most suitable a preliminary model actuator of shape memory alloy was developed and some parameters evaluated such as stresses, the amount of actuator movement and recovered deformation. Another model based on a model airplane wing has also been developed, varying the initial deformation and relating this to the generated voltage and the amount of rotation obtained during the drive. Based on this analysis it was concluded that the shape memory alloy can generate great stress in the system of acting and the initial deformation of the wire directly influences the stress and movement of the actuator.