Influence of large periodic sliding sequences on the electronical endurance of contacts subjected to fretting wear

In automotive applications, the low current electronical connectors need to maintain low and stable electrical contact resistance. However, they are subject to vibrations that cause severe fretting wear damage which increases the electrical contact resistance and degrades information transmission. In addition to small fretting oscillations, the connectors are subject to large clipping/unclipping operations. To investigate this aspect, combined large sliding events (+/-1000 mu m) and small fretting oscillations (+/- 9 mu m) were tested on a silver coating interface. Various sliding sequences were investigated: (a) plain fretting test, (b) five large sliding events followed by fretting cycles, and (c) sequential large sliding imposed every 10,000 fretting cycles. The study showed that the fretting electrical performance was strongly influenced by large sliding: in sequence (b) (i.e., a few large sliding events), fretting endurance decreased by about 30% compared to the plain fretting condition (a) due to the initial degradation of the silver layer. In contrast, with periodic large sliding (c), fretting endurance was multiplied by two compared to the plain fretting situation (a). The study demonstrates that periodic large sliding (i.e., clipping/unclipping) can, by removing the oxide debris layer trapped in the fretting scar, improve the electrical endurance of the contact.