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Experiments of cavitation erosion are performed on a surface using the "stationary specimen method". A small diameter horn of 5 mm is selected instead of using the standard horn of 15.9 mm. The experiments are performed according to these parameters: an excitation frequency of the horn of 20 kHz, a gap between the horn and the specimen within the range from 0.05 to 0.5 mm and the displacement amplitude of the horn within a range of 15-50 μm. After examination of the samples, two erosion patterns can be clearly distinguished, one circular shape centred in the origin and a ring shape around. Moreover, it has been observed that the diameter of this ring shape, the cavitation ring region, is a function that depends on the amplitude and the gap. Existence of the cavitation ring region under the mentioned conditions is explained using a theoretical model based on the combination of Fluid Mechanics and Analytical Mechanics. Results after application of this model reveal the satisfactory agreement between the numerical output and the experimental data.

A friction model is developed by considering the Coulomb friction model, a probabilistic approach of wear prediction, the kinematics of the pin-on-disc configuration and the elastic theory of bending. The model estimates the magnitude and direction of the frictional force, the pin torque, the probability of asperity contact and the real area of contact distinguishing between the part due to elastic and plastic asperity contacts respectively. Therefore, the proposed model is suitable for the prediction of adhesive wear. It can be applied to metal contacts for conductance characterisation through the plastically deformed asperities which is of great interest for electrical contact resistance studies.

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The effectiveness of ionic liquids as lubricants or additives has been recently studied for several tribological pairs: steel-steel, aluminium-steel and steel-titanium [1–2]. Likewise other materials used as engineering surfaces like nanocrystalline nickel coating [3], phosphor bronze [4], PVD coatings [5] and many others, have also been lubricated with ionic liquids in recent years. Most of these research studies are typically focused on the utilization of ionic liquids as neat lubricants. However, in economic terms, the use of ionic liquids as oil additives is more convenient because of its high cost.