Robert E. Cuthrell

Electric contacts. II. Mechanics of closure for gold contacts

We describe equipment and report results of a study of the mechanics of closure for gold electric contacts cleaned by sputtering and closed with precise control of mechanical and environmental variables. The ultrahigh‐vacuum system, in which measurements are performed, is isolated from building vibrations. Our measurements include contact resistance, load, cold welding, creep, anelastic strain recovery, stress strain, yield stress, and strain hardening. We calculated an activation energy of 1200 ± 100 cal/mole for low‐temperature creep in gold.

The influence of hydrogen on the deformation and fracture of the near surface region of solids: proposed origin of the Rebinder-Westwood effect

Results are presented which show the embrittling effect of hydrogen-bearing environments on the near surface region of solids. This effect was indicated by shifts to higher amplitude of the acoustic emission amplitude distributions obtained during low-speed drilling, by the drilling rate, and by scanning electron microscopy. The extent of embrittlement in liquid environments was found to depend on the availability of the hydrogen, which depends on its bonding in the liquid (covalent, partially ionized, ion paired in media of low dielectric constant, etc). The time dependence of this effect is consistent with the permeation of hydrogen in the near surface region. It is proposed that the hydrogen effect on the deformation and fracture of solids is a universal phenomenon affecting the near surface region of metals, ceramics, glasses, semiconductors, ionic crystals, minerals, and rocks (organic solids may be exceptions) and that this embrittlement by hydrogen is one of the origins of the Rebinder-Westwood chemomechanical effect.

The role of ion aggregates in Rebinder‐Westwood environmental effects on wear as monitored by acoustic emission

The acoustic‐emission rate is shown to be a direct measure of wear rate in a brittle solid and is used to study the strong dependence of drilling rates on the fluid environment. It is proposed that aggregation of ions in the drilling fluid produces charged or noncharged species which determine the surface zeta potential. The Rebinder‐Westwood environmental effects on mechanical properties correlate well with the zeta potential and it is shown that the effects also correlate well with the state of charge of ions and ion aggregates in the fluid environment.

Electrostatic forces between conducting spheres at constant potentials

A derivation in the bispherical coordinate system is presented for the electrostatic force between conducting spheres at a constant potential difference. The theoretical results are compared with experimentally measured forces.

The embrittling effects of hydrogen on a variety of inorganic materials as indicated by acoustic emission

The embrittling effects of hydrogen-bearing environments which were previously shown in detail for a few selected materials, are reported here for a wide variety of inorganic solids including glasses, ceramics, single crystal minerals, rocks, refractory coatings, semiconductors, and metals. Prior work showed the hydrogen effect using several quite different techniques and environments. The measurements for the present survey were restricted to acoustic emission amplitude distributions during drilling under carbon tetrachloride (a hydrogen-free liquid environment) and under water (a source of hydrogen). It is proposed that the hydrogen effect is a universal phenomenon which affects the deformation and fracture behaviour of solids (organic materials may be exceptions).

Surface Contaminant Characterization Using Potential-Current Curves

Results are reported of an investigation of potentialcurrent curves for the characterization of contaminants on electrical contact surfaces. It was found that pronounced leveling of the potential (decreasing contact resistance) occurs as the junction temperature is raised through the melting temperature of the contaminants. Thus the characteristic shape of potential-current curves may be used to distinguish between low- and high-melting organic contaminants and between these and oxides or refractory particles. This in situ diagnostic test has found recent industrial application in the manufacture of sensitive switches and in troubleshooting switches after prolonged inactive storage in the field.

The Bonding Characteristics of Gold in Ultrahigh Vacuum

The results are reported of a study of the factors which affect the solid-phase bonding of gold wire electrical leads. Gold surfaces were cleaned by sputtering and joined with precise control of mechanical and environmental variables. Contact resistance measurements as a function of load, coefficients of adhesion, and laser interference fringe photo-microtopographs were used as diagnostics to show the effects of cleaning, annealing, loading, and creep. Ultrahigh vacuum techniques and vibration isolation were essential to reproducibly forming and measuring the strengths of solid-phase bonds between gold samples and between gold and tungsten.

Near‐surface embrittlement of solids by hydrogen—The origin of the Rebinder‐Westwood chemomechanical effects

Well‐controlled drilling experiments in an ultrahigh‐vacuum system indicate that the Rebinder‐Westwood environmental effect on the deformation and fracture properties of Pyrex glass may be a result of embrittlement of the near‐surface region by hydrogen.

Electric contacts. I. Application of interference fringe microscopy to electric contact problems

The utility of laser interference fringe microscopy is demonstrated in a variety of electric contact problems. The technique is used for quantitative surface topography, measurement of load‐bearing areas, lubricant film characterization, wetting angle measurements, and particulate contaminant size determinations.

Evaluation of electrical contact materials for mercury switches designed to detect angular rotation

The adherence of mercury to a variety of materials was evaluated for various surface treatments in terms of contact angle and maximum meniscus height on separation. It was found that arcing markedly increased wettability and that roughening produced mercury repellent surfaces.