Optimising contact conditions between components can be critical to ensure proper operation. By reflecting sound waves off an interface, it is possible to accurately measure and monitor contact pressure and area.
Some example contact pressure plots
Using ultrasonic reflectometry, it is possible detect contact between two surfaces, but it is also possible to accurately characterise the contact area and measure the contact pressure profile of an interface in situ in real time. With a measurement frequency up to 100kHz, even the most brief of passing contacts can be detected, such as a high speed train or the passing of a single cutting tool blade.
These sensors are particularly useful for monitoring a change in contact pressure over time, for example in a bolted joint, a press fit or a seal. The technology is a very powerful tool to give scientists and researchers valuable empirical contact pressure and area measurements to feed into analytical or finite element models. It is also useful for leak detection or to detect if a foreign body such as some wear debris has entered a contact.
Thise measurements are all achieved non-invasively without effecting the contact conditions in any way. By mounting a sensor in a remote location, a sound wave is reflected from the interface and the reflected wave in encoded with information about the contact.
Our client wanted to know the contact pressure and area of the contact interface of a high pressure swaged metal-to-metal seal. Ultrasonic sensors were fitted to the external wall of the component during swaging. These values where then used to validate their finite element models.
Contact pressure measurement over time from single sensor. Contact pressure distribution from multiple sensors
By mounted ultrasonic sensors of the wheel or on the rail, it is possible to accurately measure the contact pressure and area of the interface. This can be used in the lab to validate computational models and on the track to establish service intervals.
A. Rovira,A. Roda, M.B. Marshall, H. Brunskill, R. Lewis, Experimental and numerical modelling of wheel–rail contact and wear, Wear, Volume 271, issues 5-6, 22 June 2011, Pages 911–924
H.P. Brunskill, L. Zhou, R. Lewis, M.B. Marshall, R.S. Dwyer-Joyce, Dynamic Characterisation of the Wheel/Rail Contact using Ultrasonic Reflectometry, Proceedings of the 9th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems, (CM2012), Chengdu, China, August 27-30, 2012
R. Dwyer-Joyce, C. Yao, R. Lewis roger, H. Brunskill, An ultrasonic sensor for monitoring wheel flange/rail gauge corner contact, Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit March 2013 vol. 227 no. 2 188-195
D. M. Mulvihill, H. Brunskill, M. E. Kartal, R. S. Dwyer-Joyce, D. Nowell, A Comparison of Contact Stiffness Measurements Obtained by the Digital Image Correlation and Ultrasound Techniques, Experimental Mechanics, February 2013, Springer us, 0014-4851
MB Marshall, R Lewis, T Howard, H Brunskill, Ultrasonic measurement of self-loosening in bolted joints, Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science July 2012 vol. 226 no. 7 1869-1884
U. Fernando, P. Nott, G. Graham, A. Roberts and T. Sheldrake, H. Brunskill, L. Zhou and R. Lewis, Experimental Evaluation of the Metal-to-Metal Seal Design for High-Pressure Flexible Pipes, Proceedings of the Offshore Technology Conference, 30 April-3 May 2012, Houston, Texas, USA
R. Dwyer-Joyce, C. Yao, R. Lewis roger, H. Brunskill, An ultrasonic sensor for monitoring wheel flange contact, Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit September 21, 2012 0954409712460986