Effects of initial twist on buckling and frequency response of SMA tubes

Shape Memory Alloys (SMAs) are a group of alloys, which have distinct and superior properties compared to conventional alloys. They demonstrate two particular non - linear stress - strain behavior, Shape Memory Effect and Psedoelasticity (Superelasticity). In this paper, we have studied free vibration response and buckling critical load of SMA tubes under a torsional load and phase changes. All analyzes were done using the ABAQUS finite element software. Since the modeling of SMA are not available in ABAQUS software, the UMAT subroutine in the software is used to implement the three SMA models, Boyd & Lagoudas, Liang & Rogers and Tanaka, to FE analysis. Preparing a user material subroutine enables the designer to analyze any structure that made of shape memory alloys in ABAQUS software. The effect of internal and external diameter of the constant weight tube on phase change delay, critical buckling load and natural frequency is discussed.