Method for an inline, non-destructive, fast and reliable measurement of Phase transformation temperatures of SMA in mass production processes.

SMA elements and actuators are produced as mass products in many markets such as automotive, aerospace, household applications, and consumer electronics. Beside reliable production routes, analysis methods are an important aspect of series production of SMA components. When series products are manufactured in quantities of millions, a large number of measured values are required in order to be able to assure the quality of the parts. In addition, fast and accurate measurement are required for (statistic) process control based on the functional properties of the components.

Known analysis methods such as DSC, tensile tests and product-specific climate chamber test often require extensive preparation, have long measurement durations, and are usually complex or even impossible to integrate into the manufacturing process. Furthermore, most methods are destructive and thus can only be performed on small sample sizes. Other non-destructive tests, such as R(T) measurements, are more difficult to handle with larger cross-sections, so that disturbance variables distort the measurement signal or a relatively high effort must be made to make the measurement signal evaluable.

For this purpose, a simple measurement arrangement was set up to measure the phase transformation temperatures on finished, unprepared SMA components within a few minutes. The experiments carried out show that the measurement concept is feasible and demonstrate great potential for implementation as a standard measurement method in automated, series production processes.