An improved electrical contact resistance (ECR) model for elastic rough electrode contact is proposed, incorporating the effects of asperity interactions and temperature rise by frictional and joule heating. The analytical simulation results show that the ECR decreases steeply at the beginning of the contact between Al and Cu. However, it becomes stabilized after reaching a specific contact force. It is also found that the longer elapsed sliding contact time, the higher ECR due to the increase in electrical resistivity of electrode materials by the frictional temperature rise at the interface. The effects of surface roughness parameters on ECR are studied through the 32 full-factorial design-of-experiment analysis. Based on the two representative roughness parameters, i.e., root-mean-square (rms) roughness and asperity radius, their individual and coupled effects on the saturated ECR are examined. The saturated ECR increases with the rms roughness for a rough machined surface condition, but it is hardly affected by the asperity radius. On the other hand, the saturated ECR increases with both the rms roughness and the asperity radius under a smooth thin film surface condition.
Many types of electrical connectors are used in traditional and emerging technology sectors such as electric vehicles, traditional automobiles, and aircraft, in which they need to maintain a stable and low electrical contact resistance (ECR). However, external shock and vibration can cause a sudden increase in ECR, which can lead to system failures due to electrical discontinuities or power transfer loss. In this study, the impact of structural dynamics on the ECR response is investigated using an analytical modeling and simulation. A structural vibration of 100 Hz with a surface displacement amplitude of 3 nm is applied to an electrical connector system, and the dynamic ECR response is analyzed with respect to the structural stiffness and damping ratio. At the onset of structural vibration, the system shows a high frequency ECR response with large amplitude variation, which decays over the elapsed time. From the parametric simulations and statistical data analysis, it is observed that the magnitude of ECR fluctuation decreases with the structural stiffness and damping ratio. Within the tested range of structural properties, the ECR fluctuation is more sensitive to the stiffness than the damping ratio.
Nanocarbon products and graphene derivatives are often applied to base lubricants as an additive to reduce contactinduced surface failures and improve the reliability of engineering applications. In this study, the effects of modified graphene oxide (MGO) on the lubricity of the ionic liquid (IL), 1-heptyl-3-methyl imidazolium bis[(trifluoromethane)sulfonyl]amide ([C 7 C 1 im][NTf 2 ]), are investigated through systematic experiments and material characterizations. To enhance the stability of the dispersion of GO in the IL [C 7 C 1 im][NTf 2 ] lubricant, 1-butyl-3-(9-carboxynonyl)imidazolium bromide (ILC 9 -COOH) is covalently grafted onto GO, which produces ILC 9 -COOH-modified graphene oxide (MGO). The synthesized MGO/IL lubricant is applied to the sliding contact between the stainless steel ball and the bearing steel plate. The measured friction and wear are analyzed with respect to the MGO concentration and temperature. The experimental results support that MGO is an effective additive to the IL [C 7 C 1 im][NTf 2 ] lubricant in decreasing the friction, and its benefit is more obvious at the higher temperature. From the analysis of the 3D surface profilometer and scanning electron microscopy (SEM) measurements, it is found that the abrasive type of wear is dominant on the worn surface. If the MGO concentration is appropriately controlled, MGO additive can be beneficial in decreasing the wear at the higher temperature.
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