Estimation of contact pressure in machine focusing on instantaneous frequency and phase of ultrasonic pulse.

Abstract

There are many contact interfaces in machines, and contact pressure on the interfaces strongly affects machine performance. Some contact interfaces include lubricants, and they become liquid layers. This study proposes a novel evaluation method for measuring contact pressure by using ultrasonic waves. Ultrasonic pulse projected onto contact interface including lubricants is multiply reflected in liquid layer. This pulse changes depending on the thickness of the liquid layer on the contact interface, but the change is very small. Therefore, we tried to evaluate contact pressure by observing the instantaneous frequency and phase distribution. The phase distribution of interfered pulse has singularity point, and the point includes pulse parameter. In this paper, we proposed a highly reproducible shim ring shape first. And, we quantitatively evaluated the gap thickness using the phase distribution. Additionally, we considered the change of shim ring by finite element method and microscope imaging to confirm validity of the estimated result by the phase distribution.