CHARACTERIZATION OF NICKEL-RICH NITINOL ALLOYS FOR ACTUATOR DEVELOPMENT

Recently a nickel-rich Ni-Ti alloy was used to fabricate compact, lightweight, and robust SMA actuators for a flight test of morphing aerostructures. Chevrons are serrated aerodynamic devices along the trailing edge of a jet engine that have been shown to reduce jet noise. In 2005 Boeing successfully flight-tested morphing chevrons on a Boeing 777-300ER with GE-115B engines. In this paper the properties and characteristics of the Ni-40Ti (% by weight) alloy used for the flight test actuators are compared to those of Ni-45Ti and Ni-43Ti. The mechanical properties, transition temperatures, dimensional stability, 2-way shape memory effect, and the response to various heat treatments are reported for each alloy. The suitability of the nickel-rich alloys for actuator development is demonstrated using performance data from the flight test. The unique properties of the nickel-rich alloys, including material reliability and transition temperature stability, are shown to be invaluable to the successful development of morphing aerostructures.