Ultrasonic Characterisation of an Interference Fit

摘要

When components such as bearings or gears are pressed onto a shaft the resulting interference induces a pressure at the interface. The size of this pressure is important as many components fail because fatigue initiates from press-fit stress concentrations. The aim of this work was to develop ultrasound as a tool to non-destructively determine press-fit contact pressures. A press-fit interface is essentially a rough surface contact and consequently behaves as a spring. If the pressure is high there are few air gaps; so it is very stiff and allows transmission of an ultrasonic wave. If the pressure is low then interface stiffness is lower and most ultrasound is reflected. A spring model was used to determine maps of contact stiffness from interference fit ultrasonic reflection data. A calibration procedure was then used to determine the pressure. In the central part of the fits, the pressures agreed closely with predictions obtained by the Lame equations. At the edges, however, stress concentrations were observed.