Shape memory alloy coil-shaped clamp for enhanced normal force in electrical connectors

Many electrical connectors experience a significant degradation in performance due to fretting corrosion, which is particularly problematic when the connector undergoes vibration. Fretting corrosion can be reduced or eliminated if the relative motion between the pin and receptacle is reduced or eliminated. One practical means of reducing the relative motion is to increase the normal force between the pin and receptacle. Unfortunately, increasing the normal force has traditionally implied increasing the insertion and removal forces required for mating and separation of the pin and receptacle. In this paper we propose a unique solution to the linked problems of fretting corrosion and insertion/removal forces. Using our approach, the normal force between the pin and receptacle is increased after the connector is mated and decreased before separation. We implement our approach for connectors that are put in service in elevated temperature environments by placing a coiled shape memory alloy (SMA) wire around the receptacle part of the connector. We will describe our concept and discuss our early experiments in which we demonstrate the effect of the SMA on the normal force under realistic conditions. In addition, we will describe future experiments designed to simulate lifetime tests on these connectors undergoing vibrations and to ascertain the effects of a large number of temperature cycles on the properties of the SMA.