Z. O. Jedlicka, Technical University of Ostrava, Ostrava, Czech Republic
An accurate measurement of a Shape Memory Alloy's (SMA) transition temperatures is necessary for the development of actuators. The apparatus is used to obtain SMA transition temperatures associated with changes in alloy chemical composition, fabrication process and forming method. The apparatus consist of “pushrod dilatometer”, contact-less resistance measurement, heating/cooling unit and sample temperature measurement. Time/temperature dependence of tested sample can be used as thermal analysis, so three characteristics are sensed simultaneously. Temperature span of the measurement is from temperature of liquid nitrogen up to 473 K. Peltier cooling unit is used if so low negative temperature is not required.
There is little data directly correlating a material's thermal properties with its performance in an actuator, particularly for durations of thousands thermal cycles.
Summary: The apparatus was developed for measurement of shape memory alloy's transition temperatures, especially for thermal cycling. Three characteristics of tested sample are measured simultaneously, so it is particularly suitable for measurement of thousands thermal cycles. The characteristics are: thermal expansion, resistance and thermal analysis. Change of sample is simple due to contact-less electrical resistance measurement. Temperature span of the measurement is from 174 K up to 473 K.
