LAUSR

Previously triboplasma was discovered in the rear gap of the sliding contact. Recently, the temperature of the triboplasma was successfully measured and demonstrated that the triboplasma is the non-equilibrium low-temperature plasma. During the course of the temperature rise distribution measurement of the triboplasma, flow of the triboplasma was observed. In this article, the triboplasma flow behaviors were investigated by measuring the triboplasma temperature rise distribution using a highly sensitive microscopic infrared camera. The measurement was performed in the tribosystem while a diamond pin with a tip radius of 4 mm slides on a sapphire disk with the wear track diameter of 40 mm in dry sliding in the ambient air under the normal forces of FN = 1 N and 2 N and the disk rotational velocities of ω = 10, 20, 50, 100, and 155 rpm, which correspond to the sliding velocities of V = 0.021, 0.042, 0.105, 0.21, and 0.324 m/s, respectively. In the experiments, the pin and disk specimens were warmed to raise the negligibly small temperature rise of the rear plasma tail region to the infrared camera imaging detection level by transferring the specimen’s heat to the plasma. Two types of plasma flows have been observed. One of them is a lamellar flow under the rotational velocity region of ω ≦ 10 rpm (V ≦ 0.021 m/s). This laminar flow transits to the turbulent one under ω ≧ 20 rpm (V ≧ 0.042 m/s). At the lamellar flow region, the triboplasma flows in the direction of sliding. However, at the turbulent flow region, the plasma flow direction shifts clockwise from the sliding line to the direction of disk rotation. The flow angle between the sliding line and the plasma flow one increases with the rotational velocity due to the centrifugal forces by disk rotation.