Development and Performance of Multi-Wire Shape Memory Effect Actuators

Recent work using TiNi foam connectors has allowed the development  of multi-wire bundles of Nitinol wires,  with wire diameters ranging from 25 mm to 500 mm (0.001” to 20”).  The wires are connected via a Nitinol  foaming process, which allows for each wire to be effectively welded into the Nitinol foam. The foaming process is net shape, which provides a net shape end connector, allowing for  simple and robust mechanical connections to a structure.   The technique allows for varying both the wire diameter to improve and modulate the thermal response time. Of  further interest is that the technique also allows for nesting of wires of varying transformation temperatures, and so provides  SME actuators with tailored properties, for example combining high temperature Nitinol wires with superelastic wires.  This development offers new capabilities for the actuator designer.   Examples of foam connectors will be described and the actuation properties of select actuator configurations will be discussed.