A Synergetic Model to Predict the Wear in Electric Contacts

The present work studies the different effects in the contact surfaces subjected to fretting movements and electric current flow on an austenitic stainless steel. The main purpose is to establish a relationship between the energy dissipation by friction and the energy dissipation by the Joule effect as well as the synergetic effects. As this type of contact is often used in a large number of small connectors, especially on the interface of printed circuit boards, there is a significant interest in studying the entire problem. Austenitic stainless steels have some properties, mainly the low oxidation rate, that, allied with relatively low cost and availability, qualify this type of material for this specific task. The fretting tests consisted in reciprocating movements on a sphere-on-flat-surface contact geometry. Both specimens were made of AISI 304 stainless steel. The electric current was kept constant during the entire test at various set values, ranging from 0 mA (no current), corresponding to no energy dissipation by the Joule effect, to 120 mA. The addition of energy in the contact by the Joule effect increases the oxidation of the contact surfaces, inducing wear acceleration in both specimens by synergetic effect. A synergetic model was introduced in order to quantify individual contributions to total wear volume, which is composed by mechanical wear, a Joule effect parcel of wear and an incremental factor of degradation due to the combined effect.