George Albert Drew

Vapor deposited thin gold coatings for high temperature electrical contacts

Using electron beam evaporation, thin films of Au over Ni and Au over Pd/sub 80/Ni/sub 20/ have been deposited on stainless steel and copper alloy substrates for high temperature electrical contact studies. The structure and composition of the films were studied in detail using electron probe microanalysis (EPMA) and X-ray photoelectron spectroscopy (XPS) with sputter depth profiling. The contact properties, such as contact resistance, fretting wear resistance, and thermal stability have been measured. The Ni and Pd/sub 80/Ni/sub 20/ layers of about 200 to 300 nm thickness have been shown to be effective in maintaining high temperature stability up to 340/spl deg/C in air by blocking the diffusion of elements in the substrates to the Au surface. These coatings also show good fretting wear resistance. These desired properties have been achieved with the thickness of the Au, Ni, and Pd/sub 80/Ni/sub 20/ layers substantially less than that of the conventional electroplated coatings.

Disengaging connectors under automotive 42 VDC loads

Connectors are designed to pass current but are generally not designed to disconnect electrical loads under power. In some circumstances, however, connectors are mated and unmated under load, as for instance during repairs, diagnostic procedures, or when blown fuses are replaced under short circuit conditions. With the present 14 VDC automotive power network no serious consequences are associated with plugging and unplugging under load due to very short break arcs (the system voltage is approximately the same as the minimum arc voltage of the contact material). For the 42 VDC PowerNet, however, serious consequences may result; impacting the reliability of the connection, the electrical distribution system, and automotive safety. The authors show component design approaches, which minimize damage when connectors are disengaged under DC loads. The connector damage is evaluated employing insertion force readings, and contact resistance measurements as part of a field correlated life test for automotive connections.

Mitigation of connector damage during disengaging DC loads using polymeric arc suppressor

Although connectors are generally not designed to disconnect electrical loads under power, in some circumstances they are mated and unmated under load. For instance, during repairs, diagnostic procedures, or when blown fuses are replaced under short circuit conditions. At dc system voltage levels significantly higher than the minimum arc voltage of metals such hot-disconnections may impact the reliability of the connection, the electrical distribution system, and automotive safety. Gassing polymers mounted onto connector terminals may reduce the damage resulting from disconnections under dc loads, and therefore enable connector designs with occasionally (forward running) arcing terminals. The authors discuss the effects of different types of gassing polymers on arc extinction and connector damage of standard automotive connectors.

Mitigation of connector damage during disengaging DC loads using polymeric arc suppressor [automotive applications]

Although connectors are generally not designed to disconnect electrical loads under power, in some circumstances they are mated and unmated under load. For instance, during repairs, diagnostic procedures, or when blown fuses are replaced under short circuit conditions. At DC system voltage levels significantly higher than the minimum arc voltage of metals such hot-disconnections may impact the reliability of the connection, the electrical distribution system, and automotive safety. Gassing polymers mounted onto connector terminals may reduce the damage resulting from disconnections under DC loads, and therefore enable connector designs with occasionally (forward running) arcing terminals. The authors discuss the effects of different types of gassing polymers on arc extinction and connector damage of standard automotive connectors.Although connectors are generally not designed to disconnect electrical loads under power, in some circumstances they are mated and unmated under load. For instance, during repairs, diagnostic procedures, or when blown fuses are replaced under short circuit conditions. At dc system voltage levels significantly higher than the minimum arc voltage of metals such hot-disconnections may impact the reliability of the connection, the electrical distribution system, and automotive safety. Gassing polymers mounted onto connector terminals may reduce the damage resulting from disconnections under dc loads, and therefore enable connector designs with occasionally (forward running) arcing terminals. The authors discuss the effects of different types of gassing polymers on arc extinction and connector damage of standard automotive connectors.

Contact welding at break of motor inrush current

The contact welding phenomenon observed at automotive relays at switch-off of a dc motor load during startup was investigated. Contact welding occurred during the first operation and was caused by anodic arcs shorter than 80 mus at breaking inrush currents of up to 85 A. The switching performance of the type of relay investigated could be correlated with the parameters: over-travel, release time, and the break current

Practical and Fundamental Studies of Nanocrystalline Composite Thin Films

Nanocrytslline composite films of Ag-Mo and Ag-Ni have been made by a co-deposition technique in UHV. The structure and composition have been studied by x-ray diffraction (XRD), transmission electron microscopy (TEM), and electron probe microanalysis (EPMA). For practical applications, the friction coefficient and wear rate were measured using a pin-on-plate machine for Ag-Mo composites deposited on steel. For fundamental studies, the hardness of the Ag-Ni composites deposited on oxidized Si wafers was measured using a nanoindenter. Experiments show that (1) reduction of friction and wear rate can be achieved using these nanocomposite coatings and (2) the hardness of the nanocomposites depends on the grain size. As the grain size of the Ag decreases from 100 to 10 nm, the hardness increases about 4 times.

Frictional work as a sliding wear evaluation parameter [electrical contacts]

The purpose of this research paper is to demonstrate that frictional work can be used as a new and previously unused parameter in the analysis of sliding wear data. Three different applications of frictional work as a sliding wear data evaluation parameter are presented in this paper. The first application shows that frictional work is a powerful approach in the evaluation of contact lubricants. Another application demonstrates that frictional work can be used as a measurement system evaluation parameter for sliding wear machines. Finally, upper and lower limits are calculated for a control chart based on frictional work values to insure the correct operation of a sliding wear machine. These applications were successfully used and established the frictional work parameter as a useful tool in the analysis of sliding wear data.