C. Cai

A technique for modelling multiple piezoelectric layers

Control of sound reflection and transmission from an object is a very important issue. Active piezoelectric layers properly coated on the external surface of the object can be used to eliminate sound reflection and/or transmission efficiently. This paper addresses the application of piezoelectric materials for active sound reflection and transmission control in the form of active layer(s). A technique for evaluating and simulating the application effects of the piezoelectric layers is proposed. The formulation of suppression of sound reflection and/or transmission has been extended to cover two case studies.

Vibration analysis of a beam with an active constraining layer damping patch

The paper presents an analytical approach for vibration response analysis of a beam with a single active constraining layer damping (ACLD) patch. The governing equation of motion of the damped beam is first derived on the basis of the energy approach and the Lagrange equation. The contribution of the paper lies in the adoption of the third admissible function to represent the longitudinal displacements of the piezoelectric constraining layer in the ACLD patch. Comparison of the computational results from the proposed analytical and conventional analytical approaches as well as commercial FEM code reveals that the proposed analytical approach can describe the vibration responses of the actively damped beam more accurately.

An exact method for analysing sound reflection and transmission by anisotropic laminates submerged in fluids

Abstract An exact method is presented for analysing the reflection and transmission of sound waves by anisotropic laminates submerged in fluids. A matrix formulation for the submerged laminate, which can have a stack of an arbitrary number of anisotropic layers, subject to a plane sound wave is derived to obtain the reflection and transmission coefficients in the frequency domain. The coupling between the fluid and laminate is taken into account in a rigorous manner. Numerical results of the method are compared with ones from other methods as examples and very good agreement is observed. The present method is useful for designing layered structures for acoustic systems.

A study on avoiding hyper-singular integrals in exterior acoustic radiation analysis

Abstract Burton and Millers formulation (BMF) is well known for solving non-uniqueness problems in an exterior acoustic problem. In this paper, an IBMF (improved BMF) is presented by directly taking into account of the normal derivatives of solid angles on the surface. The introduction of the normal derivative of solid angles in building the Burton and Millers formulation will cause the elimination of hyper-singular terms. Here lies the advantage of improved formulation. Then, reproduction of diagonal terms (RDT) is applied to further improve singular integral in IBMF. Three cases are compared for closed axi-symmetric surfaces, including SHF (conventional surface Helmholtz formulation), IBMF and IBMF–RDT. Numerical results show that the combined scheme of IBMF–RDT is valid at all wave numbers, and gives satisfied calculating accuracy, which is about 10 times higher than that of SHF.