Ultrasonic reflection from an interface provides a method for determining the conditions at machine element contacts. The approach is based on the fact that surfaces are rough and will partially reflect a wave of ultrasound. The reflection depends on the stiffness of the interface that can, with the aid of empirical data, be related to contact pressure. The technique has been applied to two different contact applications. Interface pressure has been measured in a wheel/rail contact. The measured nominal area of contact agrees well with Hertzian predictions, but the presence of surface roughness means that the real area of contact and contact pressure are significantly higher. The contact pressure in the wheel hub/axle press fit was seen to increase at the discontinuities at the edge of the fit and internal groove. Elsewhere the pressure showed a constant deviation about a mean value. A full calibration is now required to produce a complete map of contact pressure for the wheel/axle interference fit. The spatial resolution of the ultrasonic transducer is an issue when investigating small contacts with rapid pressure changes. In this study such contacts were not probed, with the technique applied to large contacts containing only gradual pressure changes. De-convolution of measured results is possible, but because of numerical errors has only limited applicability. The method is therefore best applied to large contacts, as shown by the examples in this work.
The application of ultrasound as a tool for studying contact stresses in railway engineering component contacts
Einsatz von Ultraschall als Werkzeug zur Untersuchung der Kontaktspannungen bei Berührungen von eisenbahntechnischen Komponenten
2005
6 Seiten, 8 Bilder, 1 Tabelle, 8 Quellen
Conference paper
English
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