Wen-Hu Huang

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.

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.

Dynamic stress concentration of a circular cutout buried in semi-infinite plates subjected to flexural waves

In this paper, based on the theory of elastic thin plates, applying the image method and the wave function expansion method, multiple scattering of elastic waves and dynamic stress concentration in semi-infinite plates with a circular cutout are investigated, and the general solutions of this problem are obtained. As an example, the numerical results of dynamic stress concentration factors are graphically presented and discussed. Numerical results show that the analytical results of scattered waves and dynamic stress in semi-infinite plates are different from those in infinite plates when the distance ratio b/a is comparatively small. In the region of low frequency and long wavelength, the maximum dynamic stress concentration factors occur on the illuminated side of scattered body with θ= π, but not on the side of cutout with θ=π/2. As the incidence frequency increases (the wavelength becomes short), the dynamic stress on the illuminated side of cutout becomes little, and the dynamic stress on the shadow side becomes great.

Nonsteady Effective Thermal Conductivity of Dense Fibrous Composites with Graded Interface

The multiple scattering of thermal waves by dense fibers with a functionally graded interface in composites is considered, and the analytical solution of the nonsteady effective thermal conductivity of composites is presented. The Fourier heat conduction law is applied to analyze the propagation of thermal waves in the fibrous composite. The scattering and refraction of thermal waves by cylindrical fibers with a nonhomogeneous interface layer in the matrix are expressed by using the wave function expansion method. The theory of quasi-crystalline approximation and the conditional probability density function are employed to treat the multiple scattering of thermal waves from the dense fibers. Through analysis, it is found that the nonsteady effective thermal conductivity under higher frequencies is quite different from the steady thermal conductivity. In different regions of wave frequency, the effects of the functional form of gradation and the properties and thickness of the functionally graded layers on the nonsteady effective thermal conductivity show great differences.

Corrigendum to ‘Vibration control of beams with active constrained layer damping’

This note corrects two errors in our previous paper ( Li et al 2008 Smart Mater. Struct. 17 065036) in which the active vibration control of beams treated with active constrained layer damping (ACLD) was studied analytically. The equation of motion of the whole beam/ACLD system is deduced again using Hamiltons principle with the Rayleigh–Ritz method. Numerical results are recalculated and conclusions similar to those of Li et al ( 2008 Smart Mater. Struct. 17 065036) can also be drawn.