Effective vibro-acoustical modelling of rotationally symmetric structures

At LMSSC, Cnam, Paris, December 10th 2010, 2 p.m.

Martin Östberg
Doctorate, Department of Aeronautical and Vehicle Engineering, KTH (Royal Institute of Technology), Stockholm, Sweden

Methods for effective vibro acoustical modelling of rotationally symmetric structures are presented. The work is dealing with wave propagation in structures consisting of poro elastic and visco elastic media. The rotational symmetry of the geometries studied allows for elimination of one or two of the spatial variables, significantly reducing the computational load.
Firstly, by using a Fourier expansion for the azimuthal angle in combination with a finite element method, the full three dimesional problem may be split up into several, much smaller, orthogonal two dimensional problems. Secondly, a wave guide approach is used for the axial wave propagation when studying some specific (cylindrical) geometries and boundary conditions, further reducing the problem into a one dimensional one, to be solved numerically.
The discussed methods can be used when constructing models of larger systems, for example suspension systems in vehicles. The cylindrical (visco elastic) rubber isolators present in such systems are then modelled by means of the presented mehods and connected to the surrounding structures using e.g. a transfer matrix methodology, making available a computationally efficient tool for predicting the dynamical behaviour of vehicle suspension systems etc...

Laboratoire de Mécanique des Structures et des Systèmes Couplés - LMSSC