Feng-Ming Li

Active aeroelastic flutter analysis and vibration control of supersonic beams using the piezoelectric actuator/sensor pairs

The active vibration control of all kinds of structures by using the piezoelectric material has been extensively investigated. In this paper, the active aeroelastic flutter characteristics and vibration control of supersonic beams applying the piezoelectric material are studied further. The piezoelectric materials are bonded on the top and bottom surfaces of the beams to act as the actuator and sensor so that the active aeroelastic flutter suppression for the supersonic beams can be conducted. The supersonic piston theory is adopted to evaluate the aerodynamic pressure. Hamiltons principle with the assumed mode method is used to develop the dynamical model of the structural systems. By using the standard eigenvalue methodology, the solutions for the complex eigenvalue problem are obtained. A negative velocity feedback control strategy is used to obtain active damping. The aeroelastic flutter bounds are calculated and the active aeroelastic flutter characteristics are analyzed. The impulse responses of the structural system are obtained by using the Houbolt numerical algorithm to study the active aeroelastic vibration control. The influences of the non-dimensional aerodynamic pressure on the active flutter control are analyzed. From the numerical results it is observed that the aeroelastic flutter characteristics of the supersonic beams can be significantly improved and that the aeroelastic vibration amplitudes can be remarkably reduced, especially at the flutter points, by using the piezoelectric actuator/sensor pairs which can provide an active damping. Within a certain value of the feedback control gain, with the increase of it, the flutter aerodynamic pressure (or flutter velocity) can be increased and the control results are also improved.

Vibration control of beams with active constrained layer damping

An analytical methodology is presented to study the active vibration control of beams treated with active constrained layer damping (ACLD). This analytical method is based on the conventional theory of structural dynamics. The process of deriving equations is precise and easy to understand. Hamiltons principle with the Rayleigh–Ritz method is used to derive the equation of motion of the beam/ACLD system. By applying an appropriate external control voltage to activate the piezoelectric constraining layer, a negative velocity feedback control strategy is employed to obtain the active damping and effective vibration control. From the numerical results it is seen that the damping performances of the beam can be significantly improved by the ACLD treatment. With the increase of the control gain, the active damping characteristics are also increased. By equally dividing one ACLD patch into two and properly distributing them on the beam, one can obtain better active vibration control results than for the beam with one ACLD patch. The analytical method presented in this paper can be effectively extended to other kinds of structures.

Active vibration control of conical shells using piezoelectric materials

In this paper, the active vibration control of conical shells is studied using velocity feedback and linear quadratic regulator methods. Up to now, many researches on the active vibration control of beams, plates and cylindrical shells have been published, however, to our knowledge, few people have studied the active vibration control of conical shells. Normally, in the equation of motion of the conical shells, some coefficients are variables, which makes the equation of motion of the conical shells very complicated and difficult to solve analytically. In order to solve this problem, Hamilton’s principle with the assumed mode method is employed to derive the equation of motion of the complex electromechanical coupling system. This equation of motion for the conical shell and piezoelectric patch system can be easily solved and effectively used for the structural active vibration control. Based on the traditional theory of structural dynamics, this method is easy to understand and is verified by numerical simulations. The forced vibration responses of the conical shells with two piezoelectric patches are computed to study the active vibration control. The optimal design for the locations of the piezoelectric patches is also developed by the genetic algorithm. From the results it can be seen that the control gain has a significant effect on the vibration control of the conical shell, but the effect of the size of the piezoelectric patches on controlling the vibration amplitudes is not so obvious. The overall vibration of the conical shell can be effectively reduced by the velocity feedback control method. With the increase of the control gain, the active damping characteristics of the conical shell are improved. Moreover, the optimal placement scheme of the piezoelectric patches obtained by the genetic algorithm can significantly reduce the vibration amplitudes of the conical shell.

Flexural wave propagation in double-layered nanoplates with small scale effects

In this work, the flexural wave propagation in doubled-layered nanoplates is studied. Based on the nonlocal continuum theory, the equation of wave motion is derived. The frequency, phase velocity, group velocity, and their ratio with different scale coefficients and wave numbers are presented. From the results, it can be observed that the small scale effects should be considered for higher frequencies. The dispersion properties for mode I and mode II are different. The van der Walls (vdW) interaction has significant influence on the wave characteristics for the higher mode, which is similar to the vibration properties of nanoplates. However, not all of the characteristics for mode II can be dominated by the vdW interaction, they can be affected by the wave number and the scale coefficients.

Effects of Axial Load and Elastic Matrix on Flexural Wave Propagation in Nanotube With Nonlocal Timoshenko Beam Model

In this paper, the effects of the axial load and the elastic matrix on the flexural wave in the carbon nanotube are studied. Based on the nonlocal continuum theory and the Timoshenko beam model, the equation of the flexural wave motion is derived. The dispersion relation between the frequency and the wave number is illustrated. The characteristics of the flexural wave propagation in the carbon nanotube embedded in the elastic matrix with the axial load are analyzed. The wave frequency and the phase velocity are presented with different wave numbers. Furthermore, the small scale effects on the wave properties are discussed.

Optimal locations of piezoelectric actuators and sensors for supersonic flutter control of composite laminated panels

The optimal active flutter control of supersonic composite laminated panels is studied using the distributed piezoelectric actuators/sensors pairs. The supersonic piston theory is used to calculate the unsteady aerodynamic pressure, and Hamilton’s principle with the assumed mode method is employed to develop the equation of motion of the structural system. The controllers are designed by the proportional feedback control method and the linear quadratic Gauss (LQG) algorithm. The optimal locations of the actuator/sensor pairs are determined by the genetic algorithm (GA). The aeroelastic properties of the structural system are mainly analyzed using the frequency-domain method. The time-domain responses of the structure are also computed using the Runge–Kutta method. The influences of ply angle on the flutter bound of the laminated panel with different length–width ratios are analyzed. The optimal design for the locations for different numbers of piezoelectric patches used in the proportional feedback control is carried out through the GA. Meanwhile, the control effects using different numbers of actuator/sensor pairs are investigated. The flutter suppression by the LQG algorithm is also carried out. The control effects using the two different controllers are compared. Numerical simulations show that the optimal locations obtained by the GA can increase the critical flutter aerodynamic pressure significantly, and the LQG algorithm is more effective in flutter suppression for supersonic structures than the proportional feedback controller.

ACTIVE VIBRATION CONTROL OF FINITE L-SHAPED BEAM WITH TRAVELLING WAVE APPROACH

In this paper, the disturbance propagation and active vibration control of a finite L-shaped beam are studied. The dynamic response of the structure is obtained by the travelling wave approach. The active vibration suppression of the finite L-shaped beam is performed based on the structural vibration power flow. In the numerical calculation, the influences of the near field effect of the error sensor and the small error of the control forces on the control results are all considered. The simulation results indicate that the structural vibration response in the medium and high frequency regions can be effectively computed by the travelling wave method. The effect of the active control by controlling the power flow is much better than that by controlling the acceleration in some cases. And the control results by the power flow method are slightly affected by the locations of the error sensor and the small error of the control forces.

Band gap behaviours of periodic magnetoelectroelastic composite structures with Kagome lattices

In this paper, the elastic wave propagation in periodic cylinder magnetoelectroelastic composite structures is studied using the plane wave expansion method. The band structure characteristics of magnetoelectroelastic rods embedded in polymer matrix and the reverse case are investigated taking the electric, magnetic and mechanical coupling effects into account. The generalised eigenvalue equation is derived to analyse the in-plane and out-of-plane modes, respectively. The numerical calculations for both the cases with Kagome lattices are performed. The relation between the gap widths and filling fractions are discussed in detail. The effects of the magnetoelectricity on the band structures and widths of band gaps are analysed. The band gap characteristics are illustrated further and the results will be helpful to design such kind of composite structures.

Spectral element method and its application in analysing the vibration band gap properties of two-dimensional square lattices

In this paper, the vibration band gap properties of a two-dimensional square lattice are studied using the spectral element method. Before assembling the spectral equations of whole structures, the spectral stiffness matrices of the tensional and bending elements are established. The frequency responses of the lattices are calculated and compared with those obtained by the finite element method. It can be observed that the results in the spectral element method are more accurate, especially in high frequency ranges. The frequency band gap properties are analyzed based on the accurate frequency responses. The effects of the material and structure parameters on the band gap properties are investigated.

Nonlinear vibration of a two-dimensional composite laminated plate in subsonic air flow

The nonlinear vibration of a two-dimensional composite laminated plate in subsonic air flow with simply supported boundary conditions is investigated. Based on the von Karman’s plate theory, the equation of motion of the plate is established using Hamilton’s principle. The aerodynamic pressure induced by the coupled vibration of the plate and subsonic airflow is derived from the linear potential flow theory and compared with the existing model. The variable separation method is used to transform the equation of motion of the plate into nonlinear ordinary differential equations. The influences of the flow velocity, the length-to-thickness ratio and the ply angle of the plate on the nonlinear vibration behaviors of the plate are discussed. From the analytical and numerical results it can be seen that the critical instability velocity obtained from the present aerodynamic model is the same as the existing result. The first-order expansion of the transverse displacement can reflect the dynamic characteristics of the plate. With the increase of the flow velocity and the length-to-thickness ratio, the instability interval of the nonlinear vibration can be prolonged and the nonlinear resonance frequency can be increased. The composite laminated plate with smaller ply angle exhibits more stable dynamic properties than that with larger ply angles.