Projeto, modelagem e análise experimental de um motor rotativo acionado por molas de liga com memória de forma

Abstract

The rotation mechanism based on an eccentric, combined with large deformations of SMA spring type actuators, allowed the design of a compact device with continuous rotation. The proposed rotary motor is driven by NiTi shape memory alloy (SMA) springs. The springs are driven by an electric current using the Joule effect as a physical principle. In this case, the motor can rotate in both directions, by only inverting the drive sequence. When driven, SMA springs combine the superelastic effect (SE) and the shape memory effect (SME), and can suffer deformations of up to 600% of their initial length. To define the design parameters, an electro-thermomechanical characterization of the SMA springs was performed, in addition to antagonistic tests to evaluate the generation of work after thermal heating. An analytical model for the prior evaluation of the motor responses was implemented in function of the thermomechanical characteristics of the SMA springs. For the numerical simulations, three different models were tested in order to define which of them best represents the behavior of force and deflection of the actuators. The most appropriate model was selected for the analyses of numerical responses of the entire motor with coupled springs. An experimental setup measured the temperature, angular displacement, force and torque responses generated by the motor. The functioning of the prototype was demonstrated for different electric current drives in relation to the activation time. As main scientific contribution was obtained an energy density index of 0.001406851 Nmm/mm³, which relates the maximum experimental torque generated by the motor volume, higher than other important SMA motors in the literature.