On the design strategies for SMA-based morphing actuators: state of the art and common practices applied to a fascinating case study

The request of even more stringent restrictions, regarding efficiency and environmental impact of industrial components, determines an optimized use of primary energy but also entails the design of more lightweight, smart and flexible devices, able to adapt their operation as a function of several different inputs. In this framework, the use of a fascinating class of metallic materials, called Shape Memory Alloys (SMAs), could represent a valid support for the designers. The capability of these materials to react to an external stimulus, without continuing to supply energy to external actuators, represents, especially in the aerospace engineering field, a technological breakthrough. The present paper reports the basic ideas and summarizes the important aspects related to the development of SMA-based actuators in relation to the present state of the art. A case study of morphing blades, equipped with embedded SMA strips, for an automotive cooling fan is reported. Finally, some hints, regarding the design process of SMA-based actuators, are proposed.