Reducing Measurement Uncertainty During Characterization Of SMA Actuators Through New Mounting Solutions

Shape memory alloys (SMA) are thermally activated smart materials. They have the ability to change into a previously imprinted shape through thermal or electrical activation. This property is based on a reversible, diffusionless transition between the low temperature phase (martensite) and the high temperature phase (austenite). Due to this thermal effect, SMA are suitable as actuators in mechatronic systems. To achieve widespread acceptance of this technology, reliable material characterization and therefore standard test procedures are required. Thus the focus of this paper is on various factors influencing the measurement uncertainty of a testing method and equipment for SMA actuator applications. Important factors for reducing measurement uncertainty are mostly temperature related. Special interest lies on mounting the SMA specimens whereby the reliability of the mounting device is very important for the test procedure and the test results. Different types of SMA mounting devices for test rigs are designed taking into account SMA-specific requirements like elasticity, testing temperatures or electrical connection. These mounting devices can be compared and evaluated against each other methodically. In conclusion a recommendation for mounting SMA in a test rig is made, which can be used as a basis for a standardized test rig.