Torsional Natural Frequency Analysis Of Torsional Vibration Damper Using Numerical And Modal Test Approaches

Abstract

This work presents to obtain the torsional natural frequencies and mode shapes of the torsional vibration damper. The torsional vibration damper is mounted on the end of the crankshaft in the opposite direction of the flywheel to dampen the torsional vibrations, especially high-torque diesel engines. The torsional vibration damper used in the study consists of thirteen elements include rubber, silicone and other materials. Therefore, in this study, the Holzer, matrix, finite element methods and modal test are realized to determine the torsional natural frequencies and mode shapes of the proposed torsional vibration damper, then all obtained reaults are compared. The torsional vibration damper, consisting of thirteen elements, is reduced to five masses using the lumped-mass method, and an equivalent lumped mass model is created. This five-mass model is obtained by connecting three masses in series, two masses in series and two masses in series, and three parallel branches. The equations of the motion of the system are achieved using the equivalent model. The obtained equations of motion are used in the determination of torsional natural frequencies using the matrix method. Since the Holzer method is not suitable for the multi-parallel branched lumped-mass model, a modified approach is developed to calculate the system's natural frequencies. For the finite element method, a numerical model of the torsional vibration damper is formed using a one-to-one CAD model. Modal analysis with computer-aided finite element method is carried out with Ansys Workbench software. Finally, the values obtained by performing the modal test are accepted as reference and compared with the values of other numerical methods. Accordingly, the finite element method converged 97%, the matrix method 92% and the Holzer method 90%. Considering the linearization of materials exhibiting nonlinear behavior in the study, the developed modified Holzer method provided a satisfactory convergence.