Modal analysis and demonstration of metastructure combining local resonators and an autonomous synchronized switch damping circuit

A locally resonant metastructure is a promising approach for low-frequency vibration attenuation, whereas the attachment of many resonators results in unnecessary and multiple resonance outside the bandgap. To address this issue, we propose a damping metastructure combining local resonators and an autonomous synchronized switch damping circuit. On the basis of modal analysis, we derive an electromechanically coupled equation of the proposed metastructure. The piezo ceramics, which are attached on a small portion of the metastructure and connected to the circuit, remarkably decrease the magnitude of the resonant vibration with no extra sensors, signal processors, or power sources. The displacement at unnecessary resonance was decreased by approximately 75%. The results of the coupled analysis were similar to the experimentally observed results in terms of the location and width of the bandgap on the frequency axis and the decreased displacement for the circuit. The proposed technique can overcome the disadvantage of the metastructure.

High Efficiency Active Damping on a Fan Rotor Blade in Case Of Resonant Vibrations by Means of Piezoelectric Actuators

Severe resonant vibration is one of the main roots of turbomachinery blades failure. Forced response issues arise when the blades work in non-uniform flow fields. As a result unsteady aerodynamic pressures occur on the surfaces of the blade. If the frequency of the aerodynamic excitation matches an eigenfrequency of the blade, the vibration level may considerably increase and a drop in the life-cycle of the component could be entailed. The resonant vibration conditions could be identified at the design level by means of the Campbell diagram. Unfortunately, it is not possible to avoid all the resonant conditions, hence the mitigation of vibration has always been of the utmost importance for turbomachinery designers. Moreover an active damping system based on piezoelectric (PZT) actuators which is capable of tuning its behavior according to the resonant excitation, may be considered very attractive. In this work the forced response of a fan rotor blade, due to a stationary inlet flow distortion resulting from the presence of upstream struts, is taken into account. Some resonant conditions have been analyzed by means of Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) simulations. Thereafter a novel approach based on a proper distribution of the potential supplied to the electrodes of each PZT pair, in order to maximize the damping efficiency, is applied to the case of a plausible fan blade. The outcomes show that the proposed system is able to efficiently damp each resonant excitation and enhance the structural integrity of the blade.

Fuzzy control of a resonant vibration dryer

This thesis presents a fuzzy control method for a vibratory grain dryer. The proposed control methol maintains the resonant condition for a dynamical system having constant linear stiffness, variable mass and variable damping coefficient. The MATLAB simulation results have confirmed that the fuzzy control method based on amplitude measurement is reliable and efficient.

Fuzzy control of a resonant vibration dryer

This thesis presents a fuzzy control method for a vibratory grain dryer. The proposed control methol maintains the resonant condition for a dynamical system having constant linear stiffness, variable mass and variable damping coefficient. The MATLAB simulation results have confirmed that the fuzzy control method based on amplitude measurement is reliable and efficient.

Applying System Dynamics of Discrete Supported Track to Analyze the Rail Corrugation Causation on Curved Urban Railway Tracks

Urban rail corrugation on curved tracks with small radii causes strong howling during operation, which has been bothering subway operating companies for many years. Therefore, revealing its causes and growth is important for the comfort and safety of subway operation. Current studies believe that the occurrence of rail corrugation is largely due to the resonant vibration of the wheel-rail system. However, little attention has been paid to the key causes of the track resonance and the practical prediction of the occurrence probability of rail corrugation on the certain track. This paper intends to solve these above issues. Firstly, the practical model of predicting the rail corrugation growth is proposed based on the wheel-rail coupling interaction, the key causes of corrugation are investigated, and the sensitivity analysis is carried out, while the corrugation superposition model is introduced to the analyze the corrugation evolution as well as to validate the corrugation growth from the aspect of material friction and wear. Secondly, the impact of the key causes on the initiation and development of the rail corrugation is investigated based on the cosimulation. Finally, case studies validate the proposed theory model and method. The results show that the practical prediction model for the rail corrugation growth proposed in this paper is able to estimate the occurrence possibility of rail corrugation on a specific track, and the superharmonic resonance of the track directly excited by passing vehicles eventually leads to rail corrugation. It is also found that shortwave corrugation develops more rapidly, and adjusting the support stiffness or sleeper spacing leads to fluctuations in the corrugation wavelength and its wear rate.