Torsional Natural Frequency Analysis Of A Cranktrain System Using Holzer And Finite Element Method

Abstract

This study aims to obtain the torsional natural frequencies and mode shapes of the twelve degrees of freedom cranktrain system consisting of a flywheel, crankshaft, and torsional vibration damper elements using Holzer and finite element methods. An equivalent lumped mass model of the proposed cranktrain system is created by considering twelve masses connected with spring and damping elements. In equivalent modeling approach, eight elements of the lumped mass model are connected in series, the rest four masses are connected by three parallel branchings. Also, these four masses express the torsional vibration damper includes rubber and silicone materials. Generally, the Holzer method is often used to obtain the torsional natural frequency of multi-degree of freedom series-connected systems, therefore a parallel lumped-mass model in which three separate masses are connected to a single mass is not encountered in the literature. Thus, in this study, the Holzer method approach has been developed to determine the torsional natural frequencies of lumped-mass models obtained as multiple parallel branching. Then the modal analysis is realized using the finite element method to compare the obtained results as to the Holzer method. In modal analysis Ansys Workbench software is utilized. While the finite element model is created with 1.2 million degrees of freedom, the Holzer method's model has only twelve degrees of freedom. At the end of the study, the torsional natural frequencies obtained by the Holzer method are compared with the finite element method, and it was determined that it approached 90%.