In Situ Observation of Wax-in-Oil Flow in Rough Soft Contact

In this study, a direct observation of the dynamic behaviors of wax-in-oil flow at the rough soft contact was conducted using the optical fluorescent technique. A contact area was produced between a sliding rigid glass plate and a stationary polyurethane elastomer ball. A mixture of wax in oil was used with 90 % silicon oil and 10 % paraffin wax by weight content. It was found that wax particles played an important role at the rough soft contact, which includes the accumulating process from the inlet region of the contact area and passes through at the central region. The behavior of the entrapped wax particles depends on the soft lubrication. Experimental results show that when the speed of sliding friction has a small value, the accumulation and passing through processes of wax particles occur more slowly at the soft contact interface. A major change occurs in the scratch-like lines when the sliding speed increases with rapid change of the conformity between the sliding soft surfaces.