Comparison of numerical and ultrasonic techniques for quantifying interference fit pressures

Press fits are commonly used in manufactured assemblies, components, and machines. For example railway wheels are press or shrink fitted onto axles. Railway axles occasionally fail by fatigue resulting from the alternating rotating bending loading. The site of the fatigue crack initiation is commonly at the location of the press fit. Therefore, a good understanding is needed of the press-fit region, particularly where stress-raising effects are caused by, for example, large changes in geometry. Analytical techniques are unable to predict stresses in these areas.

In this work, an ultrasonic technique was used to measure the contact stresses in a real shaft—sleeve contact. The results were compared with finite-element models of the same components. The results from the two techniques compared well both in the centre of the fit and around the edges where the stresses were raised. Both showed good correlation with the analytical Lamé solution away from the edges. The two techniques could therefore be combined in a design tool to help remove problems with edge effects that could lead to mechanical failures.