High Rate Testing of NiTi Actuator Wire

Four commercial grades of Nitinol wire were tested in a uniaxial test rig at slow and fast cyclic actuation rates in order to understand strain evolution during near-isobaric conditions.  A thin wire diameter of 0.25 mm was selected in order to enable enhanced heat transfer and thus response time during high thermal gradient testing.  Strain evolution is compared through 1000 actuation cycles in Ni – 49.2 at.% Ti, Ni-49.4 at.% Ti, Ni-Ti-Cr, and Ni-Ti-Co.  We observe improvement in cyclic actuation stability with diminishing grain size, strengthening precipitate dispersions, and ternary alloy additions.  Future work will be discussed towards informing processing conditions for high and stable work output in wire-based low and medium temperature applications.