444 research outputs found
Fretting corrosion and the reliability of multicontact connector terminals
No full textThe harsh operating environment of the automotive application makes the semi-permanent connector susceptible to intermittent high contact resistance which eventually leads to failure. Fretting corrosion is often the cause of these failures. However, laboratory testing of sample contact materials produces results that do not correlate with commercially tested connectors. A multicontact (M-C) reliability model is developed to bring together the fundamental studies and studies conducted on commercially available connector terminals. It is based on fundamental studies of the single contact interfaces and applied to commercial multicontact terminals. The model takes into consideration firstly, that a single contact interface may recover to low contact resistance after attaining a high value and secondly, that a terminal consists of more than one contact interface. For the connector to fail, all contact interfaces have to be in the failed state at the same time
The net zero mass loss phenomenon on opening switching contacts with AC loading
No full textStudies are conducted on silver metal oxide contacts on a purposed built apparatus to investigate the extent of contact erosion under opening (break) operations. The contacts are opened between 0.1 and 0.8 ms-1 at particular point-on-wave, tPOW, of the ac waveform. Current loading of up to 30 A rms, Irms is investigated. Contact material deposition, as well as mass loss, is observed and is found to balance at particular current values and point-on-wave opening leading to a net zero mass loss on the contacts. Results are presented on mass change for each contact against the two parameters of current and point-on-wave. An arc duration characteristic, ?, is plotted against current, Irms which has a net zero mass loss. The characteristic is shown to be the same for both silver tin oxide and silver cadmium oxide but is influenced by the opening velocity. The metallic and gaseous ion transfer mechanisms of the arc discharge are presented as the main processes behind this phenomenon
Degradation of road tested automotive connectors
No full textThe automotive environment is particularly demanding on connector performance, and is characterized by large temperature changes, high humidity and corrosive atmospheres. This paper presents an initial study of connector performance in terms of temperature profiles taken from road vehicles. The temperature profiles are then simulated using empirical relationships to allow prediction of connector performance. Wire harnesses have been investigated to seek evidence of the connector degradation predicted from the temperature data. Initial indications are that the wire harness shows the type of fretting behavior associated with the temperature changes. Evidence of fretting corrosion was found at the contact interface on tin plated terminals from sealed and unsealed connectors
Intermittency phenomena in electrical connectors
No full textFretting is known to be a major cause of contact deterioration and failure, particularly in tin-plated contacts. During fretting the contact resistance generally increases slowly with time. Superimposed on this slow increase in contact resistance are rapid changes in contact resistance within fractions of a second, called intermittences or short duration discontinuities. Although intermittences have been reported by several authors, they are frequently overlooked in traditional fretting experiments and not much is known about their origin. The present study aims at filling this gap. A test apparatus has been built to measure the contact voltage-drop profile during an intermittence and fretting experiments on tin-plated copper contacts have been carried out. The results lead to a set of requirements for a model to explain intermittency phenomena
The contact resistance force relationship of an intrinsically conducting polymer interface
No full textInvestigations on contact connector materials for different applications such as in the automotive industry have focused toward the increasing interest of using conducting polymers, as compared to conventional metallic contacts. The aim is to achieve overall improvements in performance as well as cost effectiveness. Currently, extrinsic conducting polymers (ECPs) are employed as conductive coats or adhesives at contact interfaces. However, frictional abrasion within the metal doped polymer (ECP) causes fretting corrosion, which leads to instability in the contact resistance. To overcome this, intrinsically conducting polymers (ICPs) are explored. Hemispherical contact coatings were fabricated using poly(3,4-ethylenedioxythiopene) (PEDOT) or polyaniline/polyvinylchloride (PANI/PVC) commodity blends. Contact resistances were taken using four-wire resistance measurement techniques. The conductivities of in-house fabricated ICP contacts were found to be in the range of 10 2 S cm 1. The response relating the change of contact resistance under varying compression force appeared to be repeatable with minimum deviation of 2%. The surface profiles of the ICP contacts were also recorded by an optical confocal system. The initial investigation results presented in this paper were used to evaluate and validate the hypothesis of employing ICP contacts to eliminate or minimize wearing and fretting effects
Introduction
No full textA quick introduction is given as to the focus, rationale, and scope of the book. The reliability science and engineering fundamentals are addressed first of all where it is emphasized that the purpose of such science is to acquire a fuller understanding of the system under development. The first three chapters from the invited authors are introduced relating to reliability and stupidity, physics-of-failure thinking, and means for acquiring observational evidence. Cause-and-effect is underlined. The next series of chapters from invited authors are introduced relating to methods in reliability for developing components and systems. These chapters have been presented in the sequence of addressing (1) components and devices, (2) micro- and nanointegrated circuits, and (3) more complex systems. The final series of chapters in the book are introduced, which address the reliability in specific applications. Several example applications are described in detail. Also, verification techniques, block modelling, and accelerated life testing are discussed in detail.</p
Enhancing connector reliability using conducting polymer materials for minimising fretting on electrical contact interfaces
No full textA typical luxury car has in excess of 400 electrical connectors with over 3000 individual terminals. Tin plated terminals are still widely used because of particular technical and commercial advantages, but this type of plating is susceptible to fretting corrosion leading to intermittent high contact resistance. This phenomenon is well known to be the main failure mechanism impairing electrical system reliability.Novel contact materials, such as conducting polymers, are investigated in this study as a possible replacement for tin plated terminals used in the automotive wiring harness. The design concept behind using a polymer contact is to minimise any fretting motion between two contacting components by the polymer flexing or bending. Fretting studies are conducted on the polymer–tin interface showing the improved mechanical and electrical behaviour of this novel interface. A mechanical model of the polymer interface is developed showing its behaviour under fretting conditions. To achieve a “zero fretting” condition, the elastic force opposing the fretting action of the deflected polymer must be lower than the frictional force at the contac
The automotive connector: the influence of powering and lubricating a fretting contact interface
No full textThe increasing amount of telematic and other electronic systems in the modern motor vehicle demands higher performance and reliability in ever decreasing space. Over many years, connector technology has advanced but is still regarded as the weak link in the reliability chain. Fretting corrosion is thought to be the main failure mechanism causing intermittent high contact resistance.A low-frequency fretting apparatus is used in this study to induce fretting corrosion on contact samples. Low frequency is used to simulate the effect caused by different thermal expansion of connector components. Powering the contact interface under these fretting conditions delays the onset of high contact resistance. Joule heating is expected to accelerate surface oxidation, but electrical breakdown of films dominated at the levels studied (2 A, 12 V open circuit). Lubricating the interface also improves performance which is shown to be due to at least three contact enhancement mechanisms: wear reduction, oxidation retardation and improved debris dispersal
The resolution dependence of measured fractal characteristics for a real un-dismantled electrical contact interface
No full textAn electrical contact interface is visualized by rendering “contact maps” from X-ray Computer Tomography(CT) images without the need for dismantling the specimens. The contact maps consist of approximately 1500 pixels×1500 pixels with each pixel relating to an 8.0m×8.0m×8.0mvolumeat the interface. The specimens consist of bolting a cable lug to a printed circuit board. The resolution dependence of measured fractal characteristics is studied for a contact interface with a normal force of 1.6 kN. The total mechanical area of contact, Am, is found to be invariant with resolution whereas the largest contact spot size, AL, is found to decrease with higher resolution. The number of spots on the apparent area of contact is found to increase with resolution but a spot increasingly has areas of noncontact within itself at higher resolution. The fractal dimension, D, of the spot area is found to converge to 1 at lower resolution consistent with self-affinity behaviour. At higher resolution D converges to a value <2
Using optical couplers to monitor the condition of electricity infrastructure
No full textIncreases in renewable and distributed generation will change the operational characteristics of our ageing power networks. To cope with these changes improved monitoring of the performance of network infrastructure is needed. Defects developing in electrical plant give rise to partial discharge (PD) activity. This paper describes an on-line PD monitoring system based on electro-optic modulators. This technique does not require a power supply at the site of the sensors and the optical transmission of signal data is a significant advantage in electrically noisy environments. Laboratory based experiments and field trials are described, which show that this approach is feasible for HV transformers and underground cable. Intelligent filtering techniques have been developed to improve the sensitivity of detection and identify PD signals without assuming any knowledge of their characteristics
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