A fast methodology to quantify electrical-contact behaviour under fretting loading conditions

Fretting wear in electrical contacts is a serious problem in many applications, especially in the automotive industry, but also in other machines exposed to vibration. It can introduce serious electrical problems, mainly the high electrical resistance of connectors, and lead to electrical installation malfunctions. This has led to the development of numerous coating systems consisting of pure metallic materials, noble and non-noble, doped as well as soft coatings. The problem of selecting optimal surface treatment for a particular application remains. To reproduce the environmental conditions of a car engine, a fretting-test machine has been specially designed and built. Using this apparatus, most of the physical conditions, such as relative humidity, temperature, frequency, relative displacement and normal force, can be precisely controlled and monitored. A fast methodology based on incremental variation of the applied displacement amplitude has been used to quantify electrical-contact endurance. Using this approach, one soft, noble coating system and one bulk material system have been studied to determine the influence of contact loading and environmental factors on their performance. Particular attention is devoted to the sliding condition during fretting and its implications for electrical-contact performance.