The steady state response of a model of circular bladed disk with imperfection is investigated. Disk imperfection results from additional two groups of damping heads fixed on opposite ends of one diameter. These damping heads are introduced into the computing model as additional point mass, damping and stiffness. Such type of imperfection causes the bifurcation of double eigenfrequencies into pairs of close eigenfrequencies. The effect of imperfection is examined both numerically on three-dimensional nonrotating FE-model and analytically on a simplified split 2DOF model of rotating disk excited by single point harmonic force. Nonlinear friction connection is analyzed and equivalent linear damping coefficient is derived and used in the calculation procedure. It is shown that nonproportional distribution of damping strongly influences the high of resonance peaks. Some examples of response curves illustrate the dynamic properties of stationary and rotating disks with mass-damping-stiffness imperfection.

Friction forces can be advantageously used as a source of passive damping in various mechanical systems. This paper deals with an experimental modelling and numerical simulation of blades interaction by means of a friction element placed in the shroud between the blade heads. The radial force, which represents the centrifugal force acting on the friction element, determines the values of contact forces between the element and blades. The experimental set-up for a couple of non-rotating blades is described in the paper, and the measured dynamic response of two blades is documented. The same situation is modelled by means of a basic and a more complex dynamical model of two blades with a friction element. The effect of friction is studied for the case of harmonic excitation by suitable frequency and subsequent free vibration attenuation. Both mathematical models are based on the finite element method combined with lumped rigid bodies. The interaction of the friction element and blades is described by normal contact and tangential friction forces derived for particular geometrical parameters of the studied mechanical system. The performed comparison of experimental and numerical results shows the satisfactory agreement and the modelling methodology could be used for possible parameter optimization.

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Abstract. In this paper the occurrence of flutter in a simplified blade cascade is analysed. The simplified blade cascade is formed by three flat plates, which perform a kinematic harmonic motion, each with a different inter-blade phase angle. The inter-blade phase angles are chosen in order for travelling wave mode of vibration to be present. The aim of the simulations is to determine the aerodynamic damping coefficients caused by the aerodynamic forces acting on the flat plates, which show whether flutter occurs. The non-linear system of Favre-averaged NavierStokes equations in ALE formulation completed by the Spalart-Allmaras turbulence model was chosen as the mathematical model. The simulations were performed using the developed inhouse CFD software based on the discontinuous Galerkin method, which offers high order of accuracy.

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