A Highly Precise Method And Characteristic Analysis On Harmonic Coupled Vibration Of The Submerged ACLD Cylindrical Shell

Analysis for the coupled vibration and acoustic control of the submerged cylindrical shell, which is a major support structures widely employed in submarines, torpedoes and other navigational apparatus, could bring out some significant and potential application value. Meanwhile, in order to enhance the concealment properties of such kind of structures, radiation noise, scattering noise and self-noise from them should be kept in a low level. Till now, two kinds of vibration and noise control technique, i.e. passive constrained layer damping (PCLD) and active constrained layer damping (ACLD), have been widely adopted in the engineering structures due to their reliable and distinct ability in vibration and noise suppression. However, ratherish little literature could be found in the analysis on the underwater structures treated with PCLD/ACLD. The reason might be that, when solving the acoustic problem for such kind of structures, coupling between the structure-fluid-electricity, together with the complex feedback control stradegy for the voltage, should be taken into account in the same time, which make low precision would be attained when applying conventional finite element method (FEM), boundary element method (BEM) or comibined FE/BE method to achive the numerical results. Hence, it is great necessary and meaningful to establish an analytical method to obtain the acoustic pressure spetrum for the underwater PCLD/ACLD cylindrical shell. In this paper, some attempt has been done to solve the problem.Firstly, a novel PCLD/ACLD cylindrical mechanical model is established. Beginning with the basic equations for thin cylindrical shells, then considering the reciprocal internal forces acting on the interface between the basic cylindrical shell and viscoelastic layer, and the interface between the constrained layer and viscoelastic layer, and introducing the constitution relationship of the piezoelectric layr in the ACLD case, the dynamic issue for PCLD/ACLD cylindrical shells could be described by a series of control equations corresponding to a series circumferential number n. For the ACLD cylindrical shell, two kinds of control equations are set up for the simple and complete mechanical-electricity coupled models, according to the two different assumptions for the electric field in piezoelectric layer. All the control equations are formulated in the form of fist order ordinary differential matrix equation. The state variables in the matrix equation are composed of the displacement and internal forces variables, all of therm have real physical meaning. Thus, boundary conditions, whether displacement boundary or internal force boundary, could be conveniently erected into the solution of these control equations.Meanwhile, since the new- type extended homogenous capacity integration is suitable to yield the full precise results with computers when solving the first order ordinary differential matrix equation, combining this kind of precise integration technique and superposition principles, and based on the transfer matrix method, a semi-analytical and semi-numerical method is established for the control equations of PCLD/ACLD cylindrical shells. Numerical results show that the proposed method is more accurate and efficient than the common FEM.This kind of transfer matrix method is expanded into the dynamic response analysis for a fluid-filled cylindrical shell treated with PCLD, owing to representing the fluid dynamic pressure in the form of the sum of Bessel function series. In virtue of the same thought and operation, by writing the acoustic pressure in the analytical form of the sum of a series of products of sphererical Hankel functions and related Legendre functions, a wave function superposition spectrum method is developed to get the acoustic characteristic results for the underwater PCLD/ACLD cylindrical shell.Addtionally, Aiming at the deficiency of available ACLD treatment, the present paper firstly proposes to divide the piezoelectric layer equally into sub-blocks by some thin insulated layers in circumferential direction, and integrate them continuely on the viscoelastic in a whole ring. Then, control voltage implemented on each sub-blocks could be different in order to form a suitable non-uniform driving voltage distribution mode, which is suitable to control the vibration casued by changeable external excitation in real time or non-axisymmetric vibration in a general case. Based on this kind of treatment, a new control technique, namely circumferential dominant modal control strategy, is put forward. Amounts of numerical results indicate that this strategy has distinctly priority to other modal control strategy in ACLD structures.In addition, by introduing the structure volume displacement, some initial discuss is carried out for the multi-point feedback control of ACLD cylindrical shell.The modeling procedure of the PCLD/ ACLD cylindrical shell, together with the semi-analytical sovling method, could be extanded into other PCLD/ACLD beam, plates or shells with regular shape. Moreover, it provides an advantage way to find the optimum results for the parameters and control gains。...