Examinando por Autor "Zarraga Rio, Ondiz"

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    Dynamic analysis of plates with thick unconstrained layer damping
    (Elsevier Ltd, 2019-12-15) Zarraga Rio, Ondiz; Sarría, Imanol; García Barruetabeña, Jon; Cortés Martínez, Fernando
    In this work the dynamic behaviour of free layer damping plates with thick unconstrained viscoelastic layer is analysed. With this aim, the Kirchhoff–Love thin plate formulation is adapted to take shear stiffness into account by using a frequency dependent equivalent flexural stiffness. To check the validity of the proposed formulation, it is implemented in a finite element model and compared to both the Oberst model and a reference 3D solid model in terms of eigenvalues and dynamic response across a wide range of boundary conditions – clamped in all edges, free, simply supported at edges, clamped in a single edge and simply supported at corners. In all the cases the material of the viscoelastic layer presents fractional damping, its modulus thus being complex and frequency dependent. The results show that the proposed model is in good agreement with the 3D model and that it provides better accuracy than the Oberst model, specially as the thickness of the damping layer, and consequently the effect of the shear, increases. Hence, the need of developing a 3D solid model can be avoided as well as the storage and computation time problems it arises, that are specially critical in industrial practical applications
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    Eddy currents damping understood as Zener viscoelastic damping
    (Academic Press, 2023-03-17) Cortés Martínez, Fernando; Zarraga Rio, Ondiz; Sarría, Imanol; Elejabarrieta Olabarri, María Jesús
    This paper identifies and explains the eddy currents damping originated in a solid that vibrates in a magnetic field as a Zener viscoelastic model damping. For that, a coupled mechanical-electrical model is proposed for the eddy currents damping. The mechanical model is studied as a single degree-of-freedom system, and the electrical model is assumed to be a closed RL circuit. The coupling between them is given by the magnetic force originated by the motional inductance. The motion equation is obtained for the coupled system for two different excitation types: harmonic force and harmonic base motion. These motion equations include derivatives of the displacement with respect to time up to the third order. An equivalence between these motion equations and the ones derived for a viscoelastic system modelled with a Zener model is found. This allows understanding the parameters of the eddy currents model as the ones of a viscoelastic Zener model. The term related with the third order derivative is associated with relaxation, a characteristic property of viscoelastic systems. This equivalence between Zener and eddy currents damping explains forces proportional to the third order derivative that other authors have experimentally found in vibrating systems with eddy currents. The proposed model is validated both from an analytical comparison with another model of the literature and from experimental results previously published. Finally, a parametric study is carried out to show up the influence of the magnetic field and electrical properties of the model on the frequency and time responses of the system.
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    General homogenised formulation for thick viscoelastic layered structures for finite element applications
    (MDPI AG, 2020-05) Zarraga Rio, Ondiz; Sarría, Imanol; García Barruetabeña, Jon; Elejabarrieta Olabarri, María Jesús; Cortés Martínez, Fernando
    Viscoelastic layered surface treatments are widely used for passive control of vibration and noise, especially in passenger vehicles and buildings. When the viscoelastic layer is thick, the structural models must account for shear effects. In this work, a homogenised formulation for thick N-layered viscoelastic structures for finite element applications is presented, which allows for avoiding computationally expensive models based on solids. This is achieved by substituting the flexural stiffness in the governing thin beam or plate equation by a frequency dependent equivalent flexural stiffness that takes shear and the properties of the different layers into account. The formulation is applied to Free Layer Damping (FLD) and Constrained Layer Damping (CLD) beams and plates and its ability to accurately compute the eigenpairs and dynamic response is tested by implementing it in a finite element model and comparing the obtained results to those given by the standard for the application-Oberst for the FLD case and RKU for the CLD one-and to a solid model, which is used as reference. For the cases studied, the homogenised formulation is nearly as precise as the model based on solids, but requires less computational effort, and provides better results than the standard model.
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    Homogenised formulation for plates with thick constrained viscoelastic core
    (Elsevier Ltd, 2020-03) Zarraga Rio, Ondiz; Sarría, Imanol; García Barruetabeña, Jon; Cortés Martínez, Fernando
    The present work analyses the dynamic behaviour of constrained layer damping (CLD) plates with thick viscoelastic layer. The bending modes and transverse response of such plates are obtained by adapting the Kirchhoff–Love thin plate formulation so that it considers the shear stiffness by using a frequency dependent equivalent flexural stiffness. The developed formulation is introduced in a finite element model and compared to the widely used RKU model and a reference 3D solid model in terms of eigenpairs and amplitude of the response for different boundary conditions. It is concluded that the developed formulation can substitute either a 3D or RKU model as it requires less computational resources than the former and provides more accurate results than the latter.