Analysis of Unbalances Forces Using Methods of Identification and Finite Elements

The study of damage in rotating machineries is of fundamental interest in the field of machine and structure design. A rotating system supported by bearings and under some dynamic conditions can generate a variety of problems that are encountered in many different types of rotating machines. One of these problems is the unbalance due to nonhomogeneous mass distribution along the shaft. Although several methods for the identification of unbalance excitation force are available in the literature, none of them can be considered unrestricted to be applied for all rotating systems. In this study, two methodologies to identify unknown excitations, such as unbalance, have been proposed. This method is based on Fourier series and Legendre polynomials. In order to investigate the effectiveness of this methodology, a massspring-damper system with three degrees of freedom (DOF), and a rotating system considering its foundations effects have been simulated and investigated. Moreover, experimental measurements were carried out to show the agreement between the theory and practice.