The fretting sliding transition as a criterion for electrical contact performance

The fretting phenomenon in electrical contacts is a plague in electrical connector industries. It induces severe electrical distortions, high electrical contact resistance and micro cuts. A specific analysis combining different fretting tests on several coated and uncoated CuSn4 bronze substrates has been conducted. The experimental investigation showed a direct correlation between the fretting sliding condition and the electrical contact performance. The stabilized partial slip condition is sufficient to maintain a low and stable electrical resistance independent on the contact dimension and geometry. On the other hand, gross slip turns out to be disastrous for oxygen-sensitive materials. Noble material coatings, which prevent the formation of an oxidized debris layer, can only delay the electrical distortion. When the substrate is reached, high and unstable electrical resistance is again observed. Therefore, to predict the electrical performance of connectors it appears essential to determine the sliding transition amplitude between the stabilized partial slip condition and stabilized gross slip condition. FEM elasto-plastic analyses have been conducted on a 2D cylinder/plane CuSn4 contact. It was shown that the sliding transition and consequently the electrical performance of the contact can conveniently be predicted if the cyclic hardening behavior of the material and the friction law of the tribosystem are correctly identified.