Investigation of Various Bend and Free Recovery Systems for Measuring Transformation Temperatures of Nickel Titanium

Transformation temperature of Nitinol is a critical attribute to the final device performance. Currently, multiple test methods exist to determine the active austenite finish temperature (Active A_f) of an array of Nitinol devices.

The original test method used since the 1990’s, involves the operator visually monitoring the specimen until 100% recovery is reached. In contrast, the methods described in ASTM F2082 plot displacement of the material over a specified temperature range. The Active A_f is defined using the tangent or 95% recovery method.

This research will evaluate the resulting temperature differences generated between three bend and free recovery (BFR) systems.