A Study of Vibration-Induced Fretting Corrosion for Electrical Connectors

Abstract

Vibration induced fretting degradation is a widely recognized failure phenomenon. However, the basic mechanisms that control the onset and progression of such fretting behavior are not well understood and are a topic of considerable interest in the electrical connector community. In this dissertation, four research projects on this topic are described. The first two projects examined the physical characteristics of vibration-induced fretting corrosion and focused on PC-type connectors and automotive-type connectors respectively. The influence of connector design, wire tie-off length, vibration profile, and lubrication were considered. It was found that both connector designs exhibited self-consistent relative displacement amplitude thresholds for the onset of fretting corrosion regardless of the excitation frequency. Also, there was a general linear dependency upon the g-level with regard to fretting rates for single frequency excitation. A mathematical model was developed that related the early stage fretting corrosion rate to the threshold vibration levels for the connectors. Additionally, a connector lubricant was tested and observed to inhibit fretting over the amplitude and frequency ranges, as expected. The third project examined the influence of normal force and finish characteristics for vibration-induced fretting degradation. Two finish types and three normal force levels for each finish type were considered, with the objective of determining which created a larger fretting degradation. Once again, a threshold vibration level and a linear fashion resistance change of fretting were found. The relative motion transfer function was also shown to provide a good measure of the tendency to fret. Finally, a comparison of the fretting performance between two commercial connectors was performed as an application of this fretting study. The fourth and final project considered the application of FEA simulation techniques to the prediction of vibration-induced fretting degradation. A single blade/receptacle contact pair was analyzed both experimentally and with an FEA model. The same transfer functions for one type of contact pair were obtained from both simulation and experiment, and the same x-axis relative motions were observed in the simulation when the threshold fretting displacements from the experiment were used. Generally, the results from the simulation matched those from the experiment very well. The results showed that for this limited system, finite element modeling and analysis have great potential for evaluating the influence of design variations on fretting behavior.