Research on reverse engineering for rotor-bearing systems using the finite element method

The critical speed is one of the major dynamic parameters of a rotor-bearing system. Because the working speed of a rotor-bearing system continuously increases, problems of second-order and higher-order critical speed necessarily appear. The critical speed of the rotor-bearing system is obviously affected by these parameters, which include the rotor's dimensions, materials, and the stiffness of its bearings and its coupling. Identifying the relationship between these parameters and the critical speed becomes extremely important. Therefore, this study obtains the critical speed and the bearing stiffness in the rotor-bearing system by employing a reverse engineering approach, combining analysis, modal testing and order tracking. First, the finite-element model of the rotor-bearing system is developed, and this can be identified by the results of the modal testing. The Campbell diagram and the critical speed map can be obtained by the correction model combined with the gyroscopic effect. Finally, the optimization method obtains the bearing stiffness by comparing the critical speed map and testing the results of the order-tracking. This investigation provides a method to determine the dynamic characteristics and critical speed map for the rotor-bearing system, and can be used to design and develop a high-speed rotating machine, including the spindles of machine tools, and the vacuum pumps.