328 IEEE TRANSACTIONS ON COMPONENTS, PACKAGING AND MANUFACTURING TECHNOLOGY, VOL. 5, NO. 3, MARCH 2015 Fretting in Electrical Connectors Induced by Axial Vibration Haoyue Yang and George Flowers Abstract—A series of experiments were performed to investigate fretting behavior of electrical connectors subjected to axial vibration input. A random vibration test used to study vibration behavior of the connector systems revealed that multiple transverse modes were excited by the axial input. Through tests with single-frequency vibration inputs, the threshold behaviors at various frequencies for the onset of fretting corrosion were identified. It is demonstrated that the threshold amplitudes are at micrometer scale for these types of connectors. The results also exhibit that the thresholds vary with vibration frequencies, and at the frequency of one mode, the threshold is lowest over the testing spectrum. Threshold amplitudes at this mode of the connector systems with various wiring tieoff lengths were also tested. Based on the understanding of the dynamics of the connector systems, a discrete vibration model was developed to predict the threshold behavior at this mode. The estimated threshold amplitudes correlate well with the experimental results through a parametric best fit of the vibration transfer functions. Index Terms— Electrical connector, fretting corrosion, modeling, vibration. I. I NTRODUCTION F RETTING degradation is widely regarded as a primary cause for failures in electric contacts involving nonnoble metals [1]. Such corrosion is attributed to mechanical stresses and chemical reactions in the electric contact [2]. Fretting motion at the contacting interface that exposes a fresh nonnoble metal to corrosive environment generates a layer of oxide with low conductivity. The buildup of this insulating layer brings about an accelerated increase in electrical resistance and finally leads to the failure of the connector contact. During the fretting process, tremendous fluctuations of electrical resistance may occur with repeated relative motion at the contacting interface. In general, hardware tests, such as shock and vibration, should be employed before new designs and materials are incorporated in electrical connectors [3]. There has been a considerable experimental and modeling effort for developing an understanding of the phenomenon, causes, and mechanisms of the fretting corrosion. The performances of various coating materials to retard fretting degradation have been studied experimentally. Manuscript received August 30, 2014; accepted January 26, 2015. Date of publication February 23, 2015; date of current version March 5, 2015. Recommended for publication by Associate Editor Thomas J. Schoepf upon evaluation of reviewers’ comments. The authors are with the Department of Mechanical Engineering, Auburn University, Auburn, AL 36849 USA (e-mail: hzy0011@auburn.edu; flowegt@auburn.edu). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TCPMT.2015.2400394 Analytical models were developed by Malucci [4]–[6] to estimate the influences of normal contact forces, fretting amplitudes, and fretting cycles on contact corrosion. The contact resistance after certain fretting cycles and the lifetime of contacts were predicted by a model developed by Bryant [7]. Finite element (FEA) models have also been proven as a reliable approach to predict fretting behaviors. In previous research of vibration-induced fretting degradation on electrical connectors, threshold level for the onset of fretting and relationship between vibration amplitude and the rate of resistance increase have been studied through various single frequency and random vibration tests [8]–[12]. A transfer matrix method was proposed to predict the threshold behavior under single-frequency vibration at various frequencies. Another analytical model incorporated with the experimental information was presented to estimate the transients of electrical resistance at early stage of fretting development under random noise. The influence of different coatings, contact stresses, and temperatures and contaminants at the contact interface on threshold behavior was also validated. The 2-D and 3-D FEA models were developed to validate the rocking-style motion and threshold magnitude of the relative motion at the contacting interfaces of connector systems [13], [14]. A multiphysics model coupled with electric, thermal, and mechanical interaction was developed by Angadi et al. [15] to estimate contact forces, and electrical and thermal contact resistances at the interfaces of connector pairs. This paper is to extend the previous effort to study the fretting phenomenon of connector systems subjected to axial vibration excitation. Threshold amplitudes of single-frequency vibration at various frequencies are evaluated for connector systems with various tieoff lengths. The random vibration test is performed to obtain the relationship between threshold amplitudes and frequency responses of the connector systems. A simple discrete vibration model is developed to predict the threshold vibration amplitudes of these connector systems. II. EXPERIMENTAL CONFIGURATION Fig. 1 shows the basic experimental setup for a type of blade/receptacle connector pair. The blade mated to the receptacle is fixed on a shaker head that excites the connector system axially. A wire lead was attached to the receptacle, and the top end of the lead was clamped to a fixture fastened on a nonvibrating stationary testing table. The height of the fixture was adjustable to change the length of the wire lead subjected to vibration. For the given connector systems, it was difficult 2156-3950 © 2015 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.