Marko Jokić

Parameter Uncertainty Effects of Stiffeners on the Vibration of Plates

The paper concerns parameter uncertainty effects of rib-stiffeners on the vibro-acoustics of thin plate structures. To gain a deep insight into the uncertainty propagation mechanism, a simple beam-stiffened plate model is built up in the first instance. By a simple mode-based hybrid technique, both the dynamic response of the beam and the statistical energy response of the plate can be approximated as functions of the beam natural frequency variations. It is found that if the amount of beam uncertainty is small enough (e.g., the generated set of natural frequency variations is narrower than the corresponding half-power bandwidth of the resonant modes), the real part of the beam mobility tends to be affected relatively little compared to the imaginary part. As a result, only the phase part of the dynamic response of the beam tends to be affected while the amplitude part can be affected relatively slightly. This is especially true when the beam and the plate have a large dynamic mismatch. One can thus deduce that, for stiffened-panel structures, the parameter uncertainties of stiffeners tend to affect little the structure-borne-sound transmission between ribs and the panel foundations. Numerical investigations of different rib-stiffened plates were conducted to validate the main conclusions.

A Study on the Effects of Local Added Masses on the Natural and the Sound Radiation Characteristics of Thin Plate Structures

As panel-like structures are widely used in industrial products such as high speed trains, automobiles, and ships, the effects of additional attachments (e.g. lumped mass, rib-stiffeners) to the panels on their dynamic/acoustic characteristics have been investigated analytically, numerically, experimentally or combining two or all the methods in the past decades. The present study focuses on highlighting the differences among local mass effects on the vibration and the radiation behaviour of flexible modes of the flat panel structures. A simple model comprising a local mass attached to a rectangular plate surface is set up, allowing us a deep insight into how the local mass affects the inherent mode parameters and the corresponding vibration and radiation characteristics of panel structures. The influential phenomena are first investigated analytically and then verified using FE-numerical simulations. The results show that: (1) the dynamic modal parameters of flat panel structures show different sensitivity to the values of the added mass and its locations; (2) the vibration and radiation characteristics of elastic modes with the same order can be affected in quite different degrees by the same local mass attachment; and (3) the modal acoustic interactions of thin plates can be significantly affected by the local mass attachments.