In this paper, an analytical method is proposed for analyzing the dynamic behavior of cross-ply laminated combined conical–cylindrical shells. First, the exact impedance solution for each substructure is derived from the governing equations for laminated thin shells, then the total impedance matrix in the global coordinates of the combined structure with arbitrary boundary conditions is assembled by displacement continuity and force balance at the joined interface. The results for free and forced vibrations are compared and validated against published and finite-element results, and remarkable advantages in computational accuracy and efficiency of this impedance synthesis method are presented through vibration characteristics compared with the finite-element method. Finally, how the boundary conditions, semi-vertex angle, and ply angle affect the natural frequencies and dynamic responses of this joined shell is investigated.

Free and forced vibro-acoustic characteristics of fluid-filled laminated cylindrical shell under initial hydrostatic pressure are analyzed. The vibration equation of shell is based on Love's theory, and filled fluid is adopted acoustic wave equation. Initial hydrostatic pressure is introduced into shell governing equation as axial and radial direction forces. The present fluid-structure interaction model is verified by comparing the natural frequencies with those in literatures and dynamic responses with FEM results. The two results show good agreement, and on basis of this, some parameters analysis is carried out. Numerical results show that boundary condition and ply-angle have influence on natural frequencies. Hydrostatic pressure increases the stiffness of composite cylindrical shell and natural frequencies. The results of this paper could provide some suggestions for the structural design of fluid contained cross-ply laminated composite cylindrical shell.

Composite cylindrical shells are widely used in various transportation vehicles. Its vibration and radiated sound characteristics have attracted the attention of many researchers. In this paper, the vibro-acoustic characteristics of laminated composite shell are investigated using wave approach method. The dynamic response of composite shell is carried out based on the Love`s thin shell theory and compared with results solved by FEM under unit driving force. It is found that the two results are in good agreement on isotropic steel and composite shell, respectively. Additional, the vibro-acoustics characteristic of composite shell are discussed when they are filled with water. When applied to the pipe system, the vibration acceleration level of composite cylindrical shell is the same level as isotopic steel pipe. This work could provide some guidance for the vibration control of composite cylindrical shell.

In order to solve the transient noise and vibration problems caused by the water hammer when closing the valve in one ship’s trim balance system, the way of developing the structure, operation method and closing strategy of the valve was studied. Then the new valve’s control effect was verified on the full-scale trim balance system pipeline test bench. The test results showed that, the multi-channel method had a good effect both on the positive and negative pressure water hammer’s control that realized up to 24.9dB of vibration reduction and 95.4% of pressure reduction. Further applying the two-stage control strategy on the basis of the multi-channel method showed better control effect, which raised the pressure and vibration control effect up to 64.3% and 7.3dB respectively.

Conical shell is one of the most common structures in engineering, especially in airplane and ship structures. In order to reduce its vibration and radiation sound, which were widely concerned, this paper used BEM method to analysis the vibration characteristic,radiated sound and the interaction between them. Three different models were established to study the difference between conical shell in the air and under water. The numerical results demonstrate that the existence of water has great influences on the frequency and amplitudes of the radiated sound power. Due to the low density, the natural frequency of conical shell dominants the peak frequency of radiation sound in the air. And the contribution of each vibration mode to the radiation sound different from each other. The results of this study can provide some valuable suggestions for the position selection of active control actuators on conical shell.

The three-dimensional sono-elasticity method recently developed by Zou ((2014) Three-dimensional sono-elasticity of ships. PhD Dissertation, China Ship Scientific Research Center, China) and Wu ((1984) Hydroelasticity of floating bodies. PhD Dissertation, Brunel University, UK) is employed to explore the acoustic and vibrational characteristics of a propeller–shaft–hull coupled system. The acoustic field can be solved by introducing Green’s function for the ideal compressible fluid together with the Price–Wu generalized fluid–structure interface boundary conditions. The vibration of a ship structure is governed by the generalized equations, including added mass, damping and restoring coefficients. In order to discover the mechanisms underlying the acoustic and vibrational characteristics of the propeller–shaft–hull coupled system, numerical models for hull structures with a shaft and without a shaft are designated. Through modal analysis, the correlations of the line spectra of acoustic radiation and the corresponding vibration modes of the hull are clearly identified. Through further numerical analysis, the appropriate location of the base for the thrust bearing and installation schemes are recommended.

A quasi-zero stiffness (QZS) vibration isolator outperforms other passive control strategies in vibration attenuation especially in a low-frequency band, but it also has an intrinsic limitation of low roll-off rate in the effective frequency range of vibration isolation. To overcome this limitation, a two-stage QZS vibration isolation system (VIS) is proposed, in which the QZS feature is realized by combining a vertical liner spring with two parallel cam–roller–spring mechanisms. Considering a possible disengagement between the cam and the roller under large amplitude vibration, a piecewise nonlinear dynamical model is developed and approximately solved by the averaging method. The analytical solutions for amplitude–frequency relationship and force transmissibility are derived. The results reveal that the two-stage QZS VIS has both advantages of low-frequency vibration isolation and high roll-off rate. It is also found that the second resonance can be eliminated when heavy damping is present in the upper stage, and hence, a broader effective frequency range of isolation can be achieved. High intermediate mass and soft vertical springs in the lower stage are also found to result in high-quality isolation performance.

This paper presents a piece of work on hollow shaft vibration control using viscoelastic materials in torsional directions. Columned viscoelastic damper is designed as a capsule containing viscoelastic material and elastic material, the outer layer of the capsule is viscoelastic material, the inner layer is elastic material. The damper is mounted somehow into the void of the shaft. When the shaft is vibrating, the damper can provide damping for the passive control of torsional vibrations. The viscoelastic damper is designed based on the principle of dynamic absorber in theoretically. When the damper has been designed, the frequency response functions of the damping system include damper and shaft can be calculated by solving the dynamic equations, then, the damping effect of the viscoelastic damper on the hollow shaft can be obtained. It's shown that the damping effect depends on the loss factor of the viscoelastic material, and the damper can provide large damping for the hollow shaft when the loss factor of the viscoelastic material achieves its optimal value. And these conclusions can also be obtained by ANSYS software.