Transmissibility of Nickel-Titanium Shape Memory Alloy Springs

A research study was undertaken to measure the transmissibility of nickel-titanium Ni-Ti shape memory alloy SMA springs and compare the results to corresponding data on steel and Inconel springs. It was motivated by interest in an effective metal alternative to rubber-based machinery isolation mounts, with possible active control features. Ni-Ti was used due to its well known properties of shape memory and high intrinsic damping. Acceleration transmissibility was measured on a spring-mass system. Due to the distributed mass in the spring coils, standing waves occurred at high frequencies. However, due to the high intrinsic damping in Ni-Ti, the standing wave resonance peaks were as much as 20 db lower than corresponding peaks in steel and Inconel springs. Thus the capability of Ni-Ti springs for high frequency vibration isolation is significantly better than that of steel or Inconel. Also, it is judged that the Ni-Ti material could be used in a variety of other isolation mount designs with a high likelihood for further improvement in passive isolation properties. In addition, it may be possible to use the shape memory effect in active control concepts. Intrinsic damping, Shape memory alloys, Nitinol, Helical springs, Vibration, Transmissibility.