Abstract
An exact and direct modeling technique is proposed for modeling of rotor-bearing systems with arbitrary selected degrees-of-freedom. This technique is based on the combination of the transfer and dynamic stiffness matrices. The technique differs from the usual combination methods in that the global dynamic stiffness matrix for the system or the subsystem is obtained directly by rearranging the corresponding global transfer matrix. Therefore, the dimension of the global dynamic stiffness matrix is independent of the number of the elements or the substructures. In order to show the simplicity and efficiency of the method, two numerical examples are given.
Highlights
The subject of rotor-bearing dynamics has received considerable attention over the last few decades
Note that the global dynamic stiffness matrix of the substructure has the same dimension as the element transfer matrix
The global dynamic stiffness matrix [D] for the entire rotor system may be obtained by applying the standard assembly procedure of the finite element method
Summary
The subject of rotor-bearing dynamics has received considerable attention over the last few decades. In order to minimize the dynamic DOF without any loss of accuracy, a combination method was introduced by Dokainish (1972) for plate vibration problems in which the element transfer matrix was obtained directly from the element stiffness and mass matrices In recent years, this combination method has been improved by other researchers (Chiatti and Sestieri, 1979; Ohga et aI., 1983; Degen et aI., 1985) for different applications. In this article an exact and direct modelling technique for rotor-bearing systems based on the combination of transfer and dynamic stiffness matrices is presented In this technique, the entire structure is first divided into several substructures based on the required master DOF. As a by-product, the exact dynamic stiffness matrix for a rotating shaft subject to axial force can be obtained by rearranging the corresponding exact transfer matrix using the technique described here
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