DEVICE FOR FATIGUE ANALYSIS OF SHAPE MEMORY ALLOY WIRES

Armando José Morais de Azevedo¹; Rodrigo Borges Paixão¹; Rodolfo Bianco Rentes¹; Pedro Manuel Calas Lopes Pacheco¹; Paulo Pedro Kenedi¹

¹ CEFET/RJ - PPEMM - Programa de Pós-Graduação em Engenharia Mecânica e Tecnologia de Materiais

doi:10.20906/CPS/COB-2015-0353

Resumo

Shape memory alloys (SMAs) have the capability to generate large forces and displacements when subjected to thermo-mechanical loads. This effect occurs due a phase transformation process. In various applications, such as actuators, SMA elements experience cyclic loadings, making the study of fatigue behavior of this material relevant. SMAs have two types of fatigue behavior: functional fatigue and structural fatigue. Functional fatigue is related with actuation capability loss promoted by the decrease in the strain recovery observed with the increase of number of cycles. An experimental device was developed in this study to analyze the fatigue behavior of SMAs wires subjected to thermo-mechanical cycles, which are composed by a constant mechanical load and a cyclic temperature variation. Temperature cyclic variation is obtained using a controlled electrical current source: heating the wire by Joule effect through the application of the electric current, followed by air-cooling by convection. The device can be used to generate experimental curves either for functional fatigue or for structural fatigue. Experimental results show that the system behaved in an appropriate and efficient way to impose fatigue of SMAs wires, exhibiting similar behavior to those found in the literature.

Palavras-chave: Shape Memory Alloy; Smart Material; Experimental analysis; Functional fatigue