An experimentally-driven approach to model bending in a thermally activated SMA-based beam

In this paper, the bending behavior of an active SMA-based beam, made up of a NiTi alloy strip externally joined to a PA66-GF30 polymeric lamina, is examined. Firstly, experimental investigations were conducted in a purpose-built test bench where a forced airflow promoted the reverse and forward phase transformations of the NiTi strip via heating and cooling ramps. The macroscopic shape changes associated with the shape memory effect deforms the structure in the cantilevered condition. The evolution of the shape memory behavior was investigated via digital image analysis, performed at both the end of heating and the end of the thermal cycle on cooling. Next, a theoretical prediction combining the classical beam model for bending with the assumption of incomplete recovery upon cooling was developed. The theoretical results indicate good agreement with experimental data showing how the proposed approach can be effectively used to predict the behavior in bending of SMA-based actuator working in controlled recovering condition.