A comparative study of in-situ wear characterisation in reciprocating tribological contact using ultrasound

Ultrasound detection techniques have been widely used as non-destructive methods to detect cracks and measure lubricant film thickness, as well as viscosity. When ultrasonic waves are incident on boundaries, they are partly reflected and transmitted. The reflected waves give information about the medium, contact, and boundaries. In previous studies, ultrasound has been used to measure the wear size of a workpiece or pin. The current study aims to use two well-known ultrasonic methods, time-of-flight (TOF) and phase difference, to measure the wear depth in real-time for both the pin and workpiece in a dry contact. The sensitivity and accuracy of these methods are then investigated. These methods can be used to determine the wear size of a tool and workpiece for future work. In this experiment, two longitudinal transducers were used in a pulse-echo mode mounted on a pin and workpiece. The pin and plate (workpiece) were made of stainless steel. A nominal contact pressure of 0.25 MPa was applied to the pin while sliding at an oscillating speed of 50 mm/s. The attached transducer to the workpiece captured the reflected signals from the plate boundaries. These reflected waves were used to measure the wear depth of the plate only. The transducer mounted on the pin measured the TOF and phase difference of reflected waves from the pin-workpiece contact, which contains the pin's wear. The monitoring and in-situ measurements were run for 200 m. The worn pin and workpiece were scanned using a 3D optical profilometer to measure the wear depth and compare the results with ultrasound. The results showed that the phase difference gives more accurate results than the TOF (TOF) method. It was also observed that the transducer with a peak frequency of 7.25 MHz measured the wear depth with 10 times accuracy compared to the transducer with a peak frequency of 2.1 MHz.