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The experimental identification of the dynamic coefficients of two hydrodynamic journal bearings operating at constant rotational speed and under nonlinear conditions

Breńkacz Ł., Żywica G., Drosińska-Komor M.

Polish Maritime Research

2017

nr 4

108--115

Hydrodynamic bearings are commonly used in ship propulsion systems. Typically, they are calculated using numerical or experimental methods. This paper presents an experimental study through which it has been possible to estimate 24 dynamic coefficients of two hydrodynamic slide bearings operating under nonlinear conditions. During the investigation, bearing mass coefficients are identified by means of a newly developed algorithm. An impact hammer was used to excite vibration of the shaft. The approximation by means of the least squares method was applied to determine bearing dynamic coefficients. Based on the performed research, the four (i.e. two main and two crosscoupled) coefficients of stiffness, damping and mass for each bearing were obtained. The mass coefficients add up to the complex shaft weight. These values are not required for modeling dynamics of the machine because the rotor mass is usually known, however, they may serve as a good indicator to validate the correctness of the stiffness and damping coefficients determined. Additionally, the experimental research procedure was described. The signals of displacements in the bearings and the excitation forces used for determination of the bearing dynamic coefficients were shown. The study discussed in this article is about a rotor supported by two hydrodynamic bearings operating in a nonlinear manner. On the basis of computations, the results of bearing dynamic coefficients were presented for a selected speed.

Analysis of an experimental setup for structural damping identification

Hentschel O. P., Bonhage M., Panning-von Scheidt L., Wallaschek J., Denk M., Masserey P.- A.

Journal of Theoretical and Applied Mechanics

2016

Vol. 54 nr 1

27--39

In the present paper, an experimental setup for structural damping determination arising from energy dissipations within the material is presented. The experimental setup is developed in such a way that all unintended damping sources are eliminated. In this connection, priority is also given to the reproducibility of the experimental data. In addition, a vacuum chamber is developed to reduce the damping arising from the interaction with the surrounding medium. Furthermore, beam-shaped specimens are clamped in a suspended way, using screws with an apex to fix the specimens in their nodes of vibration. Then, the influence of test rig specific parameters on the damping value is analyzed. In this context, an ideal setup of the test rig is identified to measure structural damping values arising from dissipations within the material. Finally, a common model for material damping description is parameterized using the experimental data.