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Aluminum is widely used in electrical contacts due to its electrical properties and inexpensiveness when compared to copper. In this study, we investigate the influence of operating conditions like contact load (pressure), sliding speed, current, and surface roughness on the electrical and tribological behavior of the interface. The tests are conducted on a linear, pin-on-flat tribo-simulator specially designed to investigate electrical contacts under high contact pressures and high current densities. Control parameters include sliding speed, load, current, and surface roughness. The response of the interface is evaluated in the light of coefficient of friction, contact resistance, contact voltage, mass loss of pins, and interfacial temperature rise. As compared to sliding speed, load, and roughness, current is found to have the greatest influence on the various measured parameters. Under certain test conditions, the interface operates in a “voltage saturation” regime, wherein increase in current do not result in any increase in contact voltage. Within the voltage saturation regime the coefficient of friction tends to be lower, a result that is attributed to the higher temperatures associated with the higher voltage (and resulting material softening). Higher interfacial temperatures also appear to be responsible for the higher wear rates observed at higher current levels as well as lower coefficients of friction for smoother surfaces in the presence of current.

In this work, a numerical method is developed to study the liquid-mediated adhesion between 3D rough surfaces. The presence of a wetting liquid between two rough surfaces generates a negative pressure inside the liquid film, which in turn induces tensile stresses in the contact region. Opposing these tensile stresses are the compressive stresses generated at solid–solid contact spots. An iterative deterministic contact model based on influence coefficients is employed to solve the equations of elasticity and capillarity simultaneously. Results for tensile (adhesive) force, wetted radius, average gap, and contact area between the rough surfaces are obtained. The results show that sudden changes in tensile force, average gap, and contact area occur with an increase in certain parameters, suggesting an elasto-capillary instability and surface collapse.

The interaction between two elastic half-spaces coupled by a small liquid bridge is investigated theoretically. A non-dimensional number, Nc, is found to govern the interface stability. When Nc is greater than or equal to 1, the two surfaces jump into solid–solid contact. Once this occurs, the contact area will continue to expand until the two surfaces are in full contact.

A recent study showed that for a liquid bridge of volume Vo interposed between two half-spaces and originally separated by uniform gap H, the interface stability was determined by a single dimensionless parameter. When the parameter exceeds a certain value, the interface loses stability and the solid surfaces come into contact. Further, once contact is made, the contact zone will continue to spread without bound. In the present work, the interaction between two curved elastic bodies coupled via a small liquid bridge is investigated. The equilibrium configurations are determined by minimizing the total free energy stored in the interface among all provisional equilibrium configurations; i.e., those configurations consistent with the equations of elasticity and capillarity. In the case of curved bodies, the stability of the interface is governed by the above parameter as well as by a dimensionless ratio involving the liquid volume (Vo), the composite radius (R) and the original (undeformed) minimum sphere–sphere separation (H). When the interface becomes unstable, solid–solid separation cannot be sustained and contact ensues. The resulting solid–solid contact radius is found to depend on the above parameters as well as on the ratio of solid–liquid and liquid–air surface energies. Based on the numerical calculations, simple relations are found between the contact radius and the other relevant parameters.