An ultrasonic method for measurement of oil films in reciprocating rubber O-ring seals

In this study, ultrasound has been developed and applied for a rubber O-ring subjected to reciprocating sliding. Under varying reciprocating speeds (2–8 Hz) and normal loads (10–20 N), ultrasonic reflection from the sealing contact was measured for analyzing the oil film formation. Central film thickness measurements were found to be in the range of 1.8–7 µm, which were comparable to the modelling results. In addition, the oil film along the reciprocating path was measured using an array of ultrasound sensors; this mapped the oil film formation covering the length of the reciprocating stroke. The findings have concluded that the ultrasound technique is an effective approach in detecting the oil film formation and contact size for the sealing contact.