Thermomechanical behaviors of Ni-Ti shape memory alloy ribbons and their numerical modeling

The thermomechanical behaviors of Ni-Ti shape memory alloy (SMA) ribbons, associated with stress and temperature-induced transformations, are experimentally and numerically investigated A 2-D incremental formulation of an SMA model is proposed and implemented in an ABAQUS finite element program through a user-defined material (UMAT)subroutine for the purpose of predicting the thermomechanical characteristics of SMA films The evolution of stress-strain curves and phase transformation temperatures is examined with various annealing temperatures The rhombohedral phase (R-phase) transformation appears in the specimen of an SMA ribbon The uncommon behaviors of permanent elongation and partial pseudoelastic behavior are observed The 2-D SMA model with a new transformation function shows a good prediction for the hysteresis of the strain-stress curve and the recovery stress. For application of the developed numerical model of 2-D SMAs, the feasibility of the gripper actuator with the SMA ribbon is numerically demonstrated (C) 2010 Elsevier Ltd. All rights reserved