Journal of Low Frequency Noise, Vibration and Active Control
In this paper, the validation of the comfort simulation strategy on an electric Stewart Platform ... more In this paper, the validation of the comfort simulation strategy on an electric Stewart Platform under road driving scenarios is explained. First, an introduction to the vibroacoustic comfort theory in passenger cars is presented. Second, the Stewart Platform used for the validation process is explained. Third, the methodology conducted for the validation of a hexapod for ride comfort applications is detailed. Finally, the Stewart Platform has been validated under real world road driving scenarios for the 6 degrees-of-freedom by means of the Vibration Dose Value. The final goal of the validation strategy of the electric Stewart Platform is to perform ride and comfort studies in a driving simulator for the 1–10 Hz frequency range.
This paper presents a robust method to estimate polymers’ damping, based on modal identification ... more This paper presents a robust method to estimate polymers’ damping, based on modal identification methods on frequency functions. The proposed method presents great advantages compared to other traditional methods such as the HPB method for polymeric materials where high damping or noise levels can limit their use. Specifically, this new method is applied on an experimental transmissibility function measured in a composite cantilever beam and the complex modulus is determined as a function of frequency. From this, a regenerated function is obtained based on the Euler–Bernoulli beam theory, and it is compared with experimental data. It can be concluded that the best way to apply the curve-fitting method for further testing of polymeric materials is when it is used with the whole frequency range by means of the MDOF method considering the residuals. In addition, this has the added advantage that the number of experimental tests to be carried out is much lower compared to using the SDOF...
This paper is aimed at investigating the influence of nonviscous modes on the vibrational respons... more This paper is aimed at investigating the influence of nonviscous modes on the vibrational response of viscoelastic systems. Thus, exponential damping models are considered. Provided that nonviscous modes disappear with time, they have influence on only the transient response of the system. Thus, the system response is obtained by means of modal superposition in order to examine the contribution of each mode. The analysis is carried out on two lumped parameter systems; systems involving a single degree and three degrees of freedom are studied. For the former, the analytic solution is derived via modal superposition and Laplace transformation. For the latter, the analytic response is contrasted with that provided via two numerical direct methods. From this investigation, it can be concluded that the system may present no oscillations, even if elastic modes are underdamped modes.
ABSTRACT This paper presents an experimental procedure for studying the influence that geometrica... more ABSTRACT This paper presents an experimental procedure for studying the influence that geometrical properties of adhesive joints have on the vibrational response of a metallic beam doubly supported on adhesive joints. A test bench has been developed for the experimental program. This procedure begins experimentally identifying the modal shapes. The beams are seismically excited and the influence of joint thickness and overlapping length on the beam motion is analyzed using the root mean square value of twenty one transmissibility functions obtained along the length of the beam. The study is performed on resonance frequencies, peak amplitudes, and modal loss factors.
The main objective of this paper is to investigate a way to characterize experimentally the mecha... more The main objective of this paper is to investigate a way to characterize experimentally the mechanical behavior of low modulus adhesives. In this context, the relaxation and complex moluli master curves of a SIKAFLEX® 505 adhesive are obtained by means of dynamic mechanical thermal analysis. Firstly, the procedure carried out to prepare and to validate the test specimens is explained.
2017 IEEE 19th International Conference on Dielectric Liquids (ICDL), 2017
Effect of electric conduction phenomenon on the mixing and thermal homogenization of a dielectric... more Effect of electric conduction phenomenon on the mixing and thermal homogenization of a dielectric liquid in a spherical reservoir is experimentally and numerically studied. The working fluid is stored in a spherical reservoir with an initial non-uniform temperature distribution, and an electrode pair is placed by the central plane of the reservoir in order to make the resultant Coulomb force penetrate into the interior of the reservoir. The temperatures in three different locations of the spherical reservoir are monitored with probe thermocouples and an RTD. The net charge distribution, Coulomb force density, and the resultant velocity field at the steady-state condition are numerically presented. The numerically determined temperature distribution of the working fluid in two time steps are also provided to illustrate fluid mixing and thermal homogenization process.
Este documento presenta la memoria de Tesis para la obtencion del grado de Doctor. La investigaci... more Este documento presenta la memoria de Tesis para la obtencion del grado de Doctor. La investigacion desarrollada en la Tesis doctoral "Dynamic analysis of structural systems damped by means of single lap viscoelastic adhesive joints" se centra en investigar la respuesta dinamica de sistemas estructurales con uniones adhesivas viscoelasticas y excitados por la base, donde el comportamiento viscoelastico del material adhesivo se presenta por medio de modelos de amortiguamiento no-viscoso. El conocimiento adquirido se utiliza para mejorar el comfort vibroacustico de marcha de una cabina de ascensor. Para analizar la influencia de los modos no viscosos, se estudia analitica y numericamente sistemas discretos y continuos con amortiguamiento exponencial. Asi, se obtiene la respuesta analitica de dos formas: con y sin variables internas. Ademas, se proponen dos formulaciones de elementos finitos: una esta concebida para aplicar metodos de integracion directa y la otra se ha desar...
In this study, the development and validation of a simplified nonlinear dynamic model of a passiv... more In this study, the development and validation of a simplified nonlinear dynamic model of a passive twin-tube hydraulic shock absorber is presented. First, the experimental dynamic response is characterized. Then, the numerical model is presented where flow, pressure, displacement, and velocity are considered. Finally, the numerical–experimental correlation is performed on force-movement dynamic behavior to prove the accuracy of the proposed model. The final goal of the model is to be integrated in a real-time driving simulator for ride comfort studies.
Viscoelastic layered surface treatments are widely used for passive control of vibration and nois... more 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 applicatio...
Abstract The present work analyses the dynamic behaviour of constrained layer damping (CLD) plate... more Abstract 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.
Fractional derivative models are widely used to easily characterise more complex damping behaviou... more Fractional derivative models are widely used to easily characterise more complex damping behaviour than the viscous one, although the underlying properties are not trivial. Several studies about the mathematical properties can be found, but are usually far from the most daily applications. Thus, this paper studies the properties of structural systems whose damping is represented by a fractional model from the point of view of a mechanical engineer. First, a single-degree-of-freedom system with fractional damping is analysed. Specifically, the distribution of the poles and the dynamic response to several excitations is studied for different model parameter values highlighting dissimilarities from systems with conventional viscous damping. In fact, thanks to fractional models, particular behaviours are observed that cannot be reproduced by classical ones. Finally, the dynamics of a machine shaft supported by two bearings presenting fractional damping is analysed. The study is carried ...
Abstract In this work the dynamic behaviour of free layer damping plates with thick unconstrained... more Abstract 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.
Abstract This paper presents a finite element analysis to determine the influence of geometrical ... more Abstract This paper presents a finite element analysis to determine the influence of geometrical properties of adhesive joints on the vibrational response of a metallic beam doubly supported on adhesive joints. This research is based on a previous experimental analysis in which it was concluded that larger experiments or numerical simulations are necessary in order to separate and investigate the influence of length, thickness and material of the adhesive joint. The finite element model is previously validated using experimental results for the transient response, mode shapes and transmissibility functions. Then, for the study, the model of the beam is seismically excited and the influence of joint thickness, overlapping length and adhesive properties on the beam motion is analyzed using the root mean square value of twenty-one transmissibility functions obtained from across the length of the beam. The study analyses resonance frequencies, peak amplitudes, and modal loss factors.
Journal of Low Frequency Noise, Vibration and Active Control
In this paper, the validation of the comfort simulation strategy on an electric Stewart Platform ... more In this paper, the validation of the comfort simulation strategy on an electric Stewart Platform under road driving scenarios is explained. First, an introduction to the vibroacoustic comfort theory in passenger cars is presented. Second, the Stewart Platform used for the validation process is explained. Third, the methodology conducted for the validation of a hexapod for ride comfort applications is detailed. Finally, the Stewart Platform has been validated under real world road driving scenarios for the 6 degrees-of-freedom by means of the Vibration Dose Value. The final goal of the validation strategy of the electric Stewart Platform is to perform ride and comfort studies in a driving simulator for the 1–10 Hz frequency range.
This paper presents a robust method to estimate polymers’ damping, based on modal identification ... more This paper presents a robust method to estimate polymers’ damping, based on modal identification methods on frequency functions. The proposed method presents great advantages compared to other traditional methods such as the HPB method for polymeric materials where high damping or noise levels can limit their use. Specifically, this new method is applied on an experimental transmissibility function measured in a composite cantilever beam and the complex modulus is determined as a function of frequency. From this, a regenerated function is obtained based on the Euler–Bernoulli beam theory, and it is compared with experimental data. It can be concluded that the best way to apply the curve-fitting method for further testing of polymeric materials is when it is used with the whole frequency range by means of the MDOF method considering the residuals. In addition, this has the added advantage that the number of experimental tests to be carried out is much lower compared to using the SDOF...
This paper is aimed at investigating the influence of nonviscous modes on the vibrational respons... more This paper is aimed at investigating the influence of nonviscous modes on the vibrational response of viscoelastic systems. Thus, exponential damping models are considered. Provided that nonviscous modes disappear with time, they have influence on only the transient response of the system. Thus, the system response is obtained by means of modal superposition in order to examine the contribution of each mode. The analysis is carried out on two lumped parameter systems; systems involving a single degree and three degrees of freedom are studied. For the former, the analytic solution is derived via modal superposition and Laplace transformation. For the latter, the analytic response is contrasted with that provided via two numerical direct methods. From this investigation, it can be concluded that the system may present no oscillations, even if elastic modes are underdamped modes.
ABSTRACT This paper presents an experimental procedure for studying the influence that geometrica... more ABSTRACT This paper presents an experimental procedure for studying the influence that geometrical properties of adhesive joints have on the vibrational response of a metallic beam doubly supported on adhesive joints. A test bench has been developed for the experimental program. This procedure begins experimentally identifying the modal shapes. The beams are seismically excited and the influence of joint thickness and overlapping length on the beam motion is analyzed using the root mean square value of twenty one transmissibility functions obtained along the length of the beam. The study is performed on resonance frequencies, peak amplitudes, and modal loss factors.
The main objective of this paper is to investigate a way to characterize experimentally the mecha... more The main objective of this paper is to investigate a way to characterize experimentally the mechanical behavior of low modulus adhesives. In this context, the relaxation and complex moluli master curves of a SIKAFLEX® 505 adhesive are obtained by means of dynamic mechanical thermal analysis. Firstly, the procedure carried out to prepare and to validate the test specimens is explained.
2017 IEEE 19th International Conference on Dielectric Liquids (ICDL), 2017
Effect of electric conduction phenomenon on the mixing and thermal homogenization of a dielectric... more Effect of electric conduction phenomenon on the mixing and thermal homogenization of a dielectric liquid in a spherical reservoir is experimentally and numerically studied. The working fluid is stored in a spherical reservoir with an initial non-uniform temperature distribution, and an electrode pair is placed by the central plane of the reservoir in order to make the resultant Coulomb force penetrate into the interior of the reservoir. The temperatures in three different locations of the spherical reservoir are monitored with probe thermocouples and an RTD. The net charge distribution, Coulomb force density, and the resultant velocity field at the steady-state condition are numerically presented. The numerically determined temperature distribution of the working fluid in two time steps are also provided to illustrate fluid mixing and thermal homogenization process.
Este documento presenta la memoria de Tesis para la obtencion del grado de Doctor. La investigaci... more Este documento presenta la memoria de Tesis para la obtencion del grado de Doctor. La investigacion desarrollada en la Tesis doctoral "Dynamic analysis of structural systems damped by means of single lap viscoelastic adhesive joints" se centra en investigar la respuesta dinamica de sistemas estructurales con uniones adhesivas viscoelasticas y excitados por la base, donde el comportamiento viscoelastico del material adhesivo se presenta por medio de modelos de amortiguamiento no-viscoso. El conocimiento adquirido se utiliza para mejorar el comfort vibroacustico de marcha de una cabina de ascensor. Para analizar la influencia de los modos no viscosos, se estudia analitica y numericamente sistemas discretos y continuos con amortiguamiento exponencial. Asi, se obtiene la respuesta analitica de dos formas: con y sin variables internas. Ademas, se proponen dos formulaciones de elementos finitos: una esta concebida para aplicar metodos de integracion directa y la otra se ha desar...
In this study, the development and validation of a simplified nonlinear dynamic model of a passiv... more In this study, the development and validation of a simplified nonlinear dynamic model of a passive twin-tube hydraulic shock absorber is presented. First, the experimental dynamic response is characterized. Then, the numerical model is presented where flow, pressure, displacement, and velocity are considered. Finally, the numerical–experimental correlation is performed on force-movement dynamic behavior to prove the accuracy of the proposed model. The final goal of the model is to be integrated in a real-time driving simulator for ride comfort studies.
Viscoelastic layered surface treatments are widely used for passive control of vibration and nois... more 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 applicatio...
Abstract The present work analyses the dynamic behaviour of constrained layer damping (CLD) plate... more Abstract 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.
Fractional derivative models are widely used to easily characterise more complex damping behaviou... more Fractional derivative models are widely used to easily characterise more complex damping behaviour than the viscous one, although the underlying properties are not trivial. Several studies about the mathematical properties can be found, but are usually far from the most daily applications. Thus, this paper studies the properties of structural systems whose damping is represented by a fractional model from the point of view of a mechanical engineer. First, a single-degree-of-freedom system with fractional damping is analysed. Specifically, the distribution of the poles and the dynamic response to several excitations is studied for different model parameter values highlighting dissimilarities from systems with conventional viscous damping. In fact, thanks to fractional models, particular behaviours are observed that cannot be reproduced by classical ones. Finally, the dynamics of a machine shaft supported by two bearings presenting fractional damping is analysed. The study is carried ...
Abstract In this work the dynamic behaviour of free layer damping plates with thick unconstrained... more Abstract 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.
Abstract This paper presents a finite element analysis to determine the influence of geometrical ... more Abstract This paper presents a finite element analysis to determine the influence of geometrical properties of adhesive joints on the vibrational response of a metallic beam doubly supported on adhesive joints. This research is based on a previous experimental analysis in which it was concluded that larger experiments or numerical simulations are necessary in order to separate and investigate the influence of length, thickness and material of the adhesive joint. The finite element model is previously validated using experimental results for the transient response, mode shapes and transmissibility functions. Then, for the study, the model of the beam is seismically excited and the influence of joint thickness, overlapping length and adhesive properties on the beam motion is analyzed using the root mean square value of twenty-one transmissibility functions obtained from across the length of the beam. The study analyses resonance frequencies, peak amplitudes, and modal loss factors.
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Papers by Jon Barruetabeña