Electrical Contact Wear Research Articles

A fast methodology to quantify electrical-contact behaviour under fretting loading conditions

Fretting wear in electrical contacts is a serious problem in many applications, especially in the automotive industry, but also in other machines exposed to vibration. It can introduce serious electrical problems, mainly the high electrical resistance of connectors, and lead to electrical installation malfunctions. This has led to the development of numerous coating systems consisting of pure metallic materials, noble and non-noble, doped as well as soft coatings. The problem of selecting optimal surface treatment for a particular application remains.To reproduce the environmental conditions of a car engine, a fretting-test machine has been specially designed and built. Using this apparatus, most of the physical conditions, such as relative humidity, temperature, frequency, relative displacement and normal force, can be precisely controlled and monitored. A fast methodology based on incremental variation of the applied displacement amplitude has been used to quantify electrical-contact endurance. Using this approach, one soft, noble coating system and one bulk material system have been studied to determine the influence of contact loading and environmental factors on their performance. Particular attention is devoted to the sliding condition during fretting and its implications for electrical-contact performance.

A Finite Element Algorithm for Electromechanical Contact Problems

AbstractIn the last hundred years a lot of work is done in describing and measuring the influence of the pressure on the resistance and wear in electrical contacts. But up to now there exists a lack of knowledge in predicting and optimizing the behavior of electrical contacts with numerical simulation tools considering the pressure dependency. The present work provides a new constitutive model for the contact interface in the case of current flow and a new friction law including electrical wear phenomena. Additionally numerical investigations are made to compare the numerical results with experimental data. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Wear mechanism in graphite–copper electrical sliding contact

The electrical conduction tensor of highly anisotropic graphite is not compatible with the mechanical and tribological tensors that leads to low friction and low mechanical wear rate in sliding electrical contact. This incompatibility increases the electrical resistance and increases thus the thermal effect and the electrical contact wear. The aim of this paper is to present the tribological behaviour of couple and to discuss the effect of the antagonistic mechanical/electrical properties of polycrystalline graphite in thin rubbed layers during sliding electrical tests.

Solid armature development program at the ARDEC Electric Armaments Research Center

An experimental railgun armature program at the US Army Armament Research and Development Engineering Center is in-place and on-going. The goal of the program is to design and develop a 50 mm solid trailing arm armature that is capable of operating efficiently in the 800 kA to 1500 kA current range. An iterative design and test methodology was created to optimize the armature electrical efficiency. A six part test plan investigates the effect of armature compliance, current pulse shape, contact size and contact material on the magnitude of the muzzle voltage and the time of transition. The armature design and test plan seek to validate a candidate electrical contact wear model and establish the required relationship between compliance and optimum contact normal force for a given launch current. Currently, the affect of armature compliance and current pulse shape on the armature performance are being investigated at velocities in excess of 2.0 km/sec. As an outcome of the test program, armature quality factor has been defined as a new figure of merit for armature performance. The test results and analysis of the muzzle voltage are presented. >

A general model for sliding wear in electrical contacts

Superconducting Bi2-nPbnSr2Ca2Cu3Ox (2223) thin films were deposited by using a multi-target sputtering system. A multi-target system enables the fabrication of thin films with varying compositions. First, we tried to obtain 2223 single-phase films by using the as-grown method. However, it is difficult to remove the influence deficiency of Bi atoms at high temperatures, so only thin films with mixed crystals of Bi2Sr2Ca1Cu2Ox (2212) and 2223 were obtained. We next conducted post-annealing to improve the crystallinity of the thin films and studied the effects of substitution of Bi with Pb. As a result, single-phase 2223 thin films with a critical temperature of 108 K were obtained by optimizing the annealing conditions and the thin film composition.

A general model for sliding wear in electrical contacts

A variety of models, generally either based on abrasive, adhesive or surface fatigue wear concepts, have been used with some success in describing the sliding wear of electrical contacts. There are also empirical observations which support the individual or simultaneous occurrence of these various mechanisms in wear of such contacts. In addition to these mechanisms, which may be referred to as surface wear mechanisms, a subsurface mechanism has also been identified in recent studies of the wear of a card-edge connector system. This mechanism is associated with the plastic deformation of the substrate and can coexist with all, or any, of the surface mechanisms. In this paper, a model is developed for this subsurface mechanism and combined with models for the surface mechanisms to provide a general model for the sliding wear of contact systems. The relationships, which result from these models, are shown to agree with observed behavior in the case of a card-edge contact system. It is suggested that the method of combining the effects of several simultaneous wear mechanisms may be applicable to more general wear situations.

Wear of electrical contacts

Both electrical and mechanical wear contribute to the loss of contact material. Electrical wear due to arcing phenomena depends on the form of the contacts, a.c.- or d.c.-switching, contact speed, and contact pressure. Mechanical wear due to friction depends on the nature of the material, the form of the contacts, their relative movement, and the pressure between them. Decrease of contact wear, either by eliminating one of the causes of wear or by redesigning the contact mechanism, is of extreme importance in increasing the reliability of contacts.