  Many engineering applications of Shape Memory Alloys (SMAs) involve passing
back and forth through phase transformation many times. Repeated phase
transformation develops permanent deformations originating from the significant
distortion that phase transformation induces at the austenite-martensite
interfaces and grain boundaries. This distortion drives dislocation activity
resulting in an observable macroscopic Transformation-Induced Plastic (TRIP)
deformation, which occurs at effective stress levels much lower than the
plastic yield limit of the material. TRIP strains may accumulate up to 20%
during the lifetime of an SMA component and thus a finite strain constitutive
model is required for simulating their response. In this work, a 3-D finite
strain model is developed based on logarithmic strain which is the only strain
measure whose rate is equal to the stretching, that describes phase
transformation and TRIP deformation in a thermodynamically consistent setting.
The model is implemented in Abaqus finite element software through a
user-defined material subroutine (UMAT). Boundary value problems such as strip
and a torque tube under both pseudoelastic and actuation cyclic loadings are
performed to test the capabilities of the newly proposed model.
