Showing 2 results for Dynamic Behavior
M. Rezaee, M. M. Ettefagh, R. Fathi ,
Volume 39, Issue 1 (8-2020)
Abstract
Although the traditional automatic ball balancer (ABB) has numerous advantages, it has two major deficiencies, i.e., it has a limited balance stable region and it increases the vibration amplitude of the rotor at transient state. These deficiencies limit the applicability of ABBs. In this regard, a new type of ABB called “the Ball-spring autobalancer” has been proposed to resolve the mentioned deficiencies of the traditional ABBs. In order to investigate the capability of the Ball-spring AB in balancing rotors, it is necessary to study its dynamics accurately. The dynamics of a rotor with linear bearing equipped with a Ball-spring AB has been studied previously; however, in real situations, the bearings have nonlinear characteristics. Here, the dynamics of a rotor with nonlinear bearings equipped with a Ball-spring AB is investigated by the multiple scales method for the first time. The results show that the nonlinearity at the rotor bearings does not impair the advantages of the Ball-spring AB.
F. Hosseinlou,
Volume 40, Issue 2 (1-2022)
Abstract
Today many complex models, typically finite element models, have been employed in the analysis of jacket offshore structures. However, these comprehensive models are not readily adopted in engineering practice, especially during the preliminary design stage. As the dynamic analysis of jacket platforms is very complicated, it will be very advantageous to make a simplified computational method to assess dynamic performance of such structures. In this work a refined simplified model has been utilized to calculate dynamic responses of jacket platforms. In this regard, the model simplification based on the vibration modal data and Timoshenko’s beam equation has been employed to overcome the uncertainty problem in modeling. According to the curve fitting method on the set of frequency response functions to derive modal parameters, the concept of power spectrum density has been also used to confirm the proposed computational model.In this regard, first the behavior of the physical model in the frequency domainhas been presented and compared with the spectral results obtained from the simplified model based on Timoshenko beam. Because the modal test of the physical model was performed under the force of white noise, the dynamic responses of the simplified model were also extracted under the force of white noise using MATLAB software. In this paper, an applied mathematical model has been produced, and it has been demonstrated that the refined simplified model can reflect the real structural features.
