Rolling-element bearings are used extensively to support shafts in rotating machines due to their low friction and high load capacities. They are known to be inherently nonlinear in nature due to clearance and stiffening nonlinearities, which depend on many parameters which are difficult to quantify, such as the radial clearance. As a result, the nonlinear behaviour of the bearings is challenging to predict and consequently the bearings are regularly modelled as linear springs in rotordynamic analyses. With ever more flexible rotor designs emerging, a need for more physical bearing models arises to enable advanced non-linear rotordynamic simulations, and hence an improved understanding of the non-linear bearing behaviour is required. For this purpose, a new static test rig known as the BEaring LOading System (BELOS) has been developed at Imperial College London which allows some of these unknown bearing parameters to be identified.

The design of the rig allows accurate quantification of the nonlinear deflection curves, including zero-stiffness effects during bearing clearance and increasing stiffening behaviour under higher loads. It was demonstrated that an experimental setup can measure the bearing stiffness to a good level of accuracy. Some key bearing parameters were identified by tuning the numerical model to match the experimental results, ready for use in a nonlinear rotordynamic analysis.