Structural FE model updating of cavity systems incorporating vibro–acoustic coupling

•A structural FE model updating method for cavities incorporating acoustic loading on the structure is presented.•The method is based on eigensensitivity of coupled eigenvalues and eigenvectors.•The performance is compared with the existing inverse eigensensitivity method through a numerical example of a 3D box cavity.•The proposed method gives a better correlation and more accurate updated model of the cavities.

Finite element model updating techniques are used to update the finite element model of a structure in order to improve its correlation with the experimental dynamic test data. These techniques are well developed and extensively studied for the case of purely structural dynamic systems. However, the cavities encountered in automotive, aerospace and other transportation applications represent a class of structures in which an elastic structure encloses an acoustic medium. In such systems the dynamic characteristics of the structure are influenced by the acoustic loading due to the acoustic response in the cavity. The existing structural FE model updating approaches assume the structure to be under in-vacuo condition and hence if used for updating cavity structural FE models would not allow taking into account the effect of acoustic loading on the structural dynamic characteristics. This may adversely affect the effectiveness of updating in yielding an accurate updated FE model.This paper addresses the above issue and presents a structural FE model updating method, called ‘coupled inverse eigen-sensitivity method׳, which takes into account the acoustic loading on the structure. The method uses the experimentally identified coupled modal data on the structure as the reference data. A numerical case study of a 3D rectangular cavity backed by a flexible plate is presented to evaluate the effectiveness of the approach to obtain an accurate structural FE model. Updating is also carried out using the existing (uncoupled) inverse eigen-sensitivity method to study the influence of acoustic loading on the updating process and to study the accuracy with which the updating parameters are identified. The results obtained are also compared with those obtained by the proposed coupled inverse eigen-sensitivity method.