The experts from AC²T present in the review paper: “A review of ultrasonic reflectometry for the physical characterization of lubricated tribological contacts: history, methods, devices, and technological trends” the application possibilities of ultrasonic measurement techniques.
The paper was published on 13th November 2022 in “Tribology Letters” and is available Open Access: https://link.springer.com/article/10.1007/s11249-022-01670-8
The two parameters “lubricant film thickness” and “viscosity” of the lubricant represent two of the most important physical parameters in lubricated tribological contacts. Although they are very important in tribocontacts, their in-situ measurement is still difficult. Sensors based on ultrasonic reflectance are a class of sensing devices that allow the direct measurement of these properties. For tribologists especially, the condition changes of tribosystems are of interest, as they determine the smooth operation, proper lubrication condition or the tribosystems’ change to impending failures. Here, ultrasonic reflectance sensors can provide valuable transient information, as they are capable of measuring the evolution of film thickness and viscosity directly, non-invasive, and in-situ, thereby bringing a large benefit over classic commercial condition monitoring sensors such as vibration sensors. One example of such a non-invasive and in-situ sensor is the “triboacoustic pin” (Figure).
This paper reviews the methods of operation of ultrasonic reflectance devices, their historical evolution, limitations, potentials, and outline trends of application for the challenges faced by the tribological community and society.