Investigation on the Degradation of Stress Relaxation of Hyperbolic Wire Spring Connectors

Abstract

A hyperbolic wire spring connector is composed by a column pin mating with a receptacle formed by several wire springs assembled on special positions. This kind of connectors has multiple contacts between pin and hyperbolic wire springs, low insertion and withdrawn force and high reliability, so that they are widely used in electric connection in electronic and electrical systems. For the devices needing long storage time, such as 30 years of shelf life, the wire spring connectors used inside the devices are also required for the reliability of long-term storage. Therefore, the wire springs in the connectors will face the problem of stress relaxation under shelf conditions, which can gradually reduce the contact force between the pin and the hyperbolic wire springs, and can lead to the degradation of contact resistance. In this paper, the stress relaxation behavior of hyperbolic wire springs made of beryllium bronze was studied by accelerated experiments with high temperature based on Larsen-Miller function. The stress relaxation of wire springs was indirectly evaluated by the separation force of hyperbolic wire spring connectors every certain hour during storing in a test chamber under various temperatures. The effects of both un-mating and mating states of hyperbolic wire spring connectors with the pins on the stress relaxation were tested and compared. The degradation mechanism of the elastic materials was discussed from the microscopic point of view. Finally, the influence of stress relaxation of wire springs on electrical contact performance of the connectors for long-term storage was analyzed by the electrical contact theory.