S. Harvey, MSC Software, Santa Ana, CA
Nitinol’s unique thermo-mechanical behavior makes it an ideal candidate for lightweight actuator applications. Numerical simulations of the multi-physics of the shape memory response are possible using commercially available finite element analysis software. The present study illustrates the coupled solution of the electrical, thermal, and mechanical behavior of an SMA actuator. Specifically a voltage potential is applied over the finite element mesh of the device, and current flows through the SMA. Due to the resistivity of the SMA, the material heats and causes the SMA actuator to undergo the well know phase transformation strain. This strain causes mechanical motion of the SMA, and resulting motion of the attached actuator arm. Cooling of the device due to thermal conduction and convection, along with a return spring, bring the actuator back to its starting position. The finite element analysis software is able to solve for outputs including, but not limited to voltage, current, temperature, strains, stresses, resulting motions and forces of the actuator, accounting for material nonlinearities, geometric nonlinearities, and contact between mating components. The resulting actuator’s motion, forces, and actuation times are compared to physically measured data from a commercially available small scale SMA actuator for validation.
Summary: The present study illustrates the finite element coupled solution of the behavior of a Electrical-Thermal-Mechanical SMA (Nitinol) actuator using commercially available finite element analysis software.
