Experimental Measurement of Precision Bearing Dynamic Stiffness

Static stiffness measurement of precision bearing components by influence coefficients is complicated by the task of loading and measuring the baseline test fixture stiffness before including the bearing components. Furthermore, as the displacement of the bearing system is measured for various load conditions, the stiffness of high quality bearings may be difficult to distinguish from the test fixture stiffness. The common occurrence of inaccurate stiffness measurements has motivated this investigation of an experimental method based on frequency response function measurements. In this work the traditional static measurement that requires careful attachment and modelling of the test fixture to ‘‘ground’’ is abandoned and replaced by dynamic measurements taken from a test fixture with free boundary conditions. A complete dynamic characterization of the test fixture is shown to be unnecessary; the only measurements required are the frequency response functions at the points of attachment to the bearing components. An investigation into the effects of common measurement errors such as sensor calibration and location is also included, with an example of the proposed method. 7 1997 Academic Press Limited