Michał Guminiak

Vibrations of system of plates immersed in fluid by BEM

The vibrations problem of system of plates immersed in fluid is considered using the boundary element method. The vibrations of the system are transmitted by a fluid. This problem in hand is a coupled problem of the fluid — structure type [1], [4], [5]. The boundary integral equation is used for describing the plate motion and the hydrodynamic pressure of the surrounding liquid. The set of constant boundary elements for the plate and internal collocation points associated with lumped masses [3] and rectangular surfaces are used. To avoid calculation of singular integrals the source points are located slightly outside the plate boundary [2], [6], [7], [8], [9]. The direct version of BEM and the static fundamental solution of the Kirchhoff plate problem are used in the paper. The Betti’s theorem is used to derive the boundary integral equations for a plate in bending. This approach avoids the development of Kirchhoff forces at a plate corners and equivalent shear forces at a plate boundary [6], [7], [8], [9]. A system of plates is surrounded from all sides by the infinite fluid which is incompressible and inviscid. A fully populated hydrodynamic matrix is obtained [4], [5], [7], [8], [9]. The dimension of the problem is not increased by the addition of the fluid interaction. Free and harmonic vibrations of system of two plates were considered. Harmonic excitation force was located at the centre of single plate. Resonance curves were made for both of plates.

Defect Detection in Plates Using Dynamic Response Signals and Discrete Wavelet Transform

The paper presents the defect detection in plates considering the influence of dynamic characteristics, especially with regard to the vibration modes. The aim if this work is to detect the localization of a defect provided that damage exists in the considered plate structure. The Kirchhoff plate bending is described and solved by the Boundary Element Method (BEM). Plates have rectangular shape and different boundary conditions. The analysis of a structural response is carried out with the use of signal processing tool namely Discrete Wavelet Transformation (DWT). Defects in plates are introduced as slots near the plate boundary.

The Stability of a Steel Welded Girder with Bending and Shear Forces Included

Abstract The stability of the element of a steel welded girder subjected to bending and shear forces is considered. The considered element is a rectangular plate supported on boundary. The type of a plate boundary conditions depend on the types (thickness) of the stiffeners. Considered plate is loaded by in-plane forces causing bending and shear effects. The Finite Element Method was applied to carry out the analysis. Additionally the Boundary Element Method in terms of boundary-domain integral equation was applied to evaluate the critical shear loading.