On definition of intermittency phenomena in electrical connectors during low frequency fretting

Fretting is known to be a major cause of contact deterioration and failure in connector systems. During fretting the contact resistance generally increases slowly with time. Superimposed on this slow increase in contact resistance are rapid changes in contact resistance within fractions of a second, called intermittences or short duration discontinuities. Consideration is given to the evaluation of surface wear during the fretting process using a 3D laser scanner. The surface wear of both plated and solid surfaces are related to the frequency of the intermittency events. High speed measurements of contact voltage drop and contact current have been carried out and the results are evaluated using general contact theory. It is shown that sudden changes in contact resistance can be caused by the interaction of surface films and metallic contact combined with the melting of current carrying asperities. The latter phenomena also accounting for volt drops across the contact interface which exceed the melting voltage of the material.