Thresholds of Axial Vibration Induced Fretting Corrosion in Electrical Connectors
Type of Degreethesis
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Vibration induced fretting corrosion has been considered an important cause of failure in electrical contacts. In previous research, the basic mechanism that controls the inchoation and development of such fretting degradation has been well understood. However the vibration exciting the motion of connector systems is limited in the direction that is perpendicular to the connector and wire lead with it. In the present research, random noise and single frequency vibration tests in the axial direction of the connector system are used to induce the fretting corrosion in the connector contacts. Vibration characteristics and vibration threshold amplitudes of the connector systems with various wire lead lengths are studies by the vibration tests. The experimental results exhibit the transverse vibration of the connector pairs and wire leads with them induced by the axial vibration excitation. Several vibration modes were found in the vibration tests. The axial vibration with micrometer-scale amplitude is able to trigger the fretting degradation of this kind of connector systems. The threshold behavior at various frequencies for the onset of fretting corrosion is displayed by the experimental results. Typically the threshold amplitudes at natural frequencies are apparently lower than the ones at other frequencies. With the increase of lengths of wire leads of the connector systems, natural frequency of the major mode decreases, and the threshold amplitudes of the mode vary as a function with a non-monotonic curve. This threshold behavior is explained experimentally and by latter modeling results. A simple mathematical model is developed to relate the threshold amplitude to the dynamic properties of connectors and wiring configuration. This spring-mass-damper vibration model is built according to the vibration characteristics and fretting mechanism of the connector systems that are validated by vibration tests. The results of this model are well correlated with the experimental results.