Study on the Friction Behavior and Abnormal Conditions of Non-contact Mechanical Seal Based on Acoustic Emission

The main cause of failure in sealing friction pairs, friction wear, has presented analytical challenges due to rapidly changing and complex friction frequency characteristics. This has led to a focus on surface morphology treatment rather than direct measurement techniques in research. In this context, the present study adopted Acoustic Emission (AE) technology for direct monitoring of friction pairs, aiming to identify friction response signals during their transient contact and abrasion stages. Employing time–frequency analysis, the research delineated the state evolution of AE characteristics during the entire operational cycle of the friction pair, from start to stop. It has established the time–frequency information of AE signals in relation to the surface state of the sealing friction pair and deciphered the correlation between the friction AE signals and the surface state alterations of the friction pair. The study showed that the frequency of friction-induced signals in seals is 270 ± 40 kHz. The transition speeds for the friction pair’s state, moving from boundary lubrication to mixed lubrication and then to fluid dynamic lubrication, were identified as 200 rpm and 1000 rpm, respectively. Additionally, an escalation in signal activity was observed in dry friction scenarios and when surface defects were present in the friction pair, markedly exceeding the activity in conditions of no wear. This relationship between the friction signals and the operational state of the seal facilitates precise assessments of wear and operational integrity, underpinning the theoretical aspects of periodic wear in seal tribology.