Method and apparatus for rapid and automated characterization of SMA wires in mass production

For Shape Memory Alloy (SMA) wires to work correctly in any application, it is important that their functional properties, such as phase transformation temperatures, hysteresis, and strain, are within certain tolerances. Furthermore, it is particularly important that these properties can be kept stable in a defined production process, consistent from batch to batch. For thin wires, one batch can mean up to more than hundred kilometres. This means that a rather large number of samples must be analysed to validate compliance with the tolerance requirements.

While some properties can be determined very easily, others require time-consuming testing in a climatic chamber or a tempered medium. As a result, the cost of testing can be quite high and a sufficiently large sample size might be difficult to implement economically, regarding testing time and necessary equipment.

To overcome this issue, a method and a corresponding device have been developed which are able to analyse samples within a short time and automatically generate a report. For this purpose, the material is heated by electric current and different load cases are simulated by electromechanical drives and sensors. Through clever cross-reference measurements, a valid relationship to a measurement in an actual climatic chamber can be established, while only a fraction of the effort and time is required to perform the analysis.