Strain sensors of shape memory alloys using acoustic emissions

Composites of shape memory alloys (SMA) with a matrix have been widely studied to suppress the propagation of damage. In these studies, the SMA is used as an actuator. A multi-functional SMA as both sensor and actuator is suitable for constructing intelligent material, such as a material with a sensing and suppressing function. The damage of materials is related to the amount of strain. We studied the use of SMA wire parts as sensors to measure the amount of strain for damage estimation. The acoustic emission (AE) signals induced by phase transformation were used to measure the deformed locations and strains. We found that the deformed locations and the amount of the strain can be determined from the AE signals of SMA wires. This SMA sensor system can be used in an aluminium-SMA composite to identify the stage leading to the initial composite damage.