Nils-Erik Horlin - Academia.edu (original) (raw)
Papers by Nils-Erik Horlin
Acta Acustica United With Acustica, 2009
The most commonly used prediction techniques to study the behaviour of poro-elastic materials are... more The most commonly used prediction techniques to study the behaviour of poro-elastic materials are based on the finite element method (FEM). In the case of poro-elastic materials, certain material properties are frequency dependent. This implies that the system matrices have to be recalculated for each frequency, which is time consuming and disadvantageous for the method. As frequency increases, the model size increases drastically, such that these methods are restricted to low-frequency calculations. This paper presents a novel wave based prediction technique to solve the poro-elastic Biot wave equations in an efficient manner. wave functions that exactly satisfy the governing differential equations are used as an expansion set to describe the field variables. This leads to small model sizes and allows the method to be applied also at higher frequencies. The paper describes the basic concepts of the method and illustrates its potential through some dedicated two-dimensional validati...
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A study of hierarchical FE solutions of Biot's equations for acoustic modeing of poroelastic ... more A study of hierarchical FE solutions of Biot's equations for acoustic modeing of poroelastic medial
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Characterization of the in vacuo viscoelastic material properties of porous foams used in vehicles
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This thesis concerns the modelling of acoustical and vibrational properties of open cell porous f... more This thesis concerns the modelling of acoustical and vibrational properties of open cell porous foams in multi-layered structures, especially multi-layered panels. The object is to enable optimisation of the microscopic geometry of the foam with respect to macroscopic quantities such as sound pressure level, surface velocity, total mass or cost. The developed method is based on numerical solutions to Biot's equations were scaling laws has been used to connect the microscopic geometry of the foam to macroscopic properties such as density, flow resistivity and characteristic length. Efforts have also been made to establish a scaling law for tortuosity that allows for adaptation to different strut shapes.
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hp-extension study of a 3d hierarchical fe formulation of biot's equation for isotropic elast... more hp-extension study of a 3d hierarchical fe formulation of biot's equation for isotropic elasto-acoustic porous media
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For an accurate prediction of the low and medium frequency surface vibration and sound radiation ... more For an accurate prediction of the low and medium frequency surface vibration and sound radiation behaviour of porous materials, there is a need to improve the means of estimating their elastic and acoustic properties. The underlying reasons for this are many and of varying origin, one prominent being a poor knowledge of the geometric anisotropy of the cell microstructure in the manufactured porous materials. Another one being, the characteristic feature of such materials i.e. that their density, elasticity and dissipative properties are highly dependent upon the manufacturing process techniques and settings used. In the case of free form moulding, the geometry of the cells and the dimensions of the struts are influenced by the rise and injection flow directions and also by the effect of gravity, elongating the cells. In addition the influence of the boundaries of the mould also introduces variations in the properties of the foam block produced. Despite these complications, the need to predict and, in the end, optimise the acoustic performance of these materials, either as isolated components or as part of a multi-layer arrangement, is growing. It is driven by the increasing demands for an acoustic performance in balance with the costs, a focus which serves to increase the need for modelling their behaviour in general and the above mentioned, inherent, anisotropy in particular. The current work is focussing on the experimental part of the characterisation of the material properties which is needed in order to correctly represent the anisotropy in numerical simulation models. Then an hybrid approach based on a combination of experimental deformation, strain field mapping, flow resistivity measurement and physically based porous material acoustic Finite Element (FE) simulation modelling is described. This inverse estimation linked with high quality measurements is crucial for the determination of the anisotropic coefficients of the porous materials is illustrated here for soft foam and fibrous wool materials.
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For an accurate prediction of the low and medium frequency surface vibration and sound radiation ... more For an accurate prediction of the low and medium frequency surface vibration and sound radiation behaviour of porous materials, there is a need to improve the means of estimating their elastic and acoustic properties. The underlying reasons for this are many and of varying origin, one prominent being a poor knowledge of the geometric anisotropy of the cell microstructure in the manufactured porous materials. Another one being, the characteristic feature of such materials i.e. that their density, elasticity and dissipative properties are highly dependent upon the manufacturing process techniques and settings used. In the case of free form moulding, the geometry of the cells and the dimensions of the struts are influenced by the rise and injection flow directions and also by the effect of gravity, elongating the cells. In addition the influence of the boundaries of the mould also introduces variations in the properties of the foam block produced. Despite these complications, the need to predict and, in the end, optimise the acoustic performance of these materials, either as isolated components or as part of a multi-layer arrangement, is growing. It is driven by the increasing demands for an acoustic performance in balance with the costs, a focus which serves to increase the need for modelling their behaviour in general and the above mentioned, inherent, anisotropy in particular. The current work is focussing on the experimental part of the characterisation of the material properties which is needed in order to correctly represent the anisotropy in numerical simulation models. Then an hybrid approach based on a combination of experimental deformation, strain field mapping, flow resistivity measurement and physically based porous material acoustic Finite Element (FE) simulation modelling is described. This inverse estimation linked with high quality measurements is crucial for the determination of the anisotropic coefficients of the porous materials is illustrated here for soft foam and fibrous wool materials.
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The flow resistivity tensor, which is the inverse of the viscous permeability tensor, is one of t... more The flow resistivity tensor, which is the inverse of the viscous permeability tensor, is one of the most important material properties for the acoustic performance of open cell foams, used in acoustic treatments. Due to the manufacturing processes, these foams are most often geometrically anisotropic. This paper discusses the estimation of the flow resistivity tensor using an improvement of a previously published method by Göransson, Guastavino et al. First, flow measurements were performed for different orientations of a cubic porous sample. The modelling of the flow resistivity tensor is centred around a three-dimensional Darcy's law model in COMSOL Earth Science Module, representing the experimental set up. The simulations are performed within an optimisation loop, to determine which flow resistivity tensor gives the best fit of the simulation results to the experimental data, of volume flow and pressure drop between the inlets and outlets. The discussion focuses on the optim...
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The air flow resistivity of nine adjacent glass wool samples is measured and estimated using a pr... more The air flow resistivity of nine adjacent glass wool samples is measured and estimated using a previously published method. The samples were extracted from a large slab of glass wool material. Identifying the full flow resistivity tensors for nine adjacent cubic glass wool samples allowed for an estimation of the spatial distribution of normal and planar flow resistivity throughout the measured area. The average density of the samples tested is 27.8 kg/m 3 . In addition, the estimated flow resistivity tensors are validated by comparing the estimated flow resistivity tensors with uni-directional measurements on cylindrical samples extracted from the cubic samples tested. Furthermore, the standard measurement method was studied, providing useful insights on the effect of the sample thickness on the measured flow resistivity for an anisotropic material.
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Computer Methods in Applied Mechanics and Engineering, 2012
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The Journal of the Acoustical Society of America, 2014
Viscoelastic properties of porous materials, typical of those used in vehicles for noise insulati... more Viscoelastic properties of porous materials, typical of those used in vehicles for noise insulation and absorption, are estimated from measurements and inverse finite element procedures. The measurements are taken in a near vacuum and cover a broad frequency range: 20 Hz to 1 kHz. The almost cubic test samples were made of 25 mm foam covered by a "heavy layer" of rubber. They were mounted in a vacuum chamber on an aluminum table, which was excited in the vertical and horizontal directions with a shaker. Three kinds of response are measured allowing complete estimates of the viscoelastic moduli for isotropic materials and also providing some information on the degree of material anisotropicity. First, frequency independent properties are estimated, where dissipation is described by constant loss factors. Then, fractional derivative models that capture the variation with frequency of the stiffness and damping are adapted. The measurement setup is essentially two-dimensional and calculations are three-dimensional and for a state of plane strain. The good agreement between measured and calculated response provides some confidence in the presented procedures. If, however, the material model cannot fit the measurements well, the inverse procedure yields a certain degree of arbitrariness to the parameter estimation.
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Journal of Sound and Vibration, 2005
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The flow resistivity tensor, which is the inverse of the viscous permeability tensor, is one of t... more The flow resistivity tensor, which is the inverse of the viscous permeability tensor, is one of the most important material properties for the acoustic performance of open cell foams, used in acoustic treatments. Due to the manufacturing processes, these foams are most often geometrically anisotropic. This paper discusses the estimation of the flow resistivity tensor using an improvement of a previously published method by Göransson, Guastavino et al. First, flow measurements were performed for different orientations of a cubic porous sample. The modelling of the flow resistivity tensor is centred around a three-dimensional Darcy's law model in COMSOL Earth Science Module, representing the experimental set up. The simulations are performed within an optimisation loop, to determine which flow resistivity tensor gives the best fit of the simulation results to the experimental data, of volume flow and pressure drop between the inlets and outlets. The discussion focuses on the optim...
Bookmarks Related papers MentionsView impact
The air flow resistivity of nine adjacent glass wool samples is measured and estimated using a pr... more The air flow resistivity of nine adjacent glass wool samples is measured and estimated using a previously published method. The samples were extracted from a large slab of glass wool material. Identifying the full flow resistivity tensors for nine adjacent cubic glass wool samples allowed for an estimation of the spatial distribution of normal and planar flow resistivity throughout the measured area. The average density of the samples tested is 27.8 kg/m 3 . In addition, the estimated flow resistivity tensors are validated by comparing the estimated flow resistivity tensors with uni-directional measurements on cylindrical samples extracted from the cubic samples tested. Furthermore, the standard measurement method was studied, providing useful insights on the effect of the sample thickness on the measured flow resistivity for an anisotropic material.
Bookmarks Related papers MentionsView impact
Acta Acustica United With Acustica, 2009
The most commonly used prediction techniques to study the behaviour of poro-elastic materials are... more The most commonly used prediction techniques to study the behaviour of poro-elastic materials are based on the finite element method (FEM). In the case of poro-elastic materials, certain material properties are frequency dependent. This implies that the system matrices have to be recalculated for each frequency, which is time consuming and disadvantageous for the method. As frequency increases, the model size increases drastically, such that these methods are restricted to low-frequency calculations. This paper presents a novel wave based prediction technique to solve the poro-elastic Biot wave equations in an efficient manner. wave functions that exactly satisfy the governing differential equations are used as an expansion set to describe the field variables. This leads to small model sizes and allows the method to be applied also at higher frequencies. The paper describes the basic concepts of the method and illustrates its potential through some dedicated two-dimensional validati...
Bookmarks Related papers MentionsView impact
A study of hierarchical FE solutions of Biot's equations for acoustic modeing of poroelastic ... more A study of hierarchical FE solutions of Biot's equations for acoustic modeing of poroelastic medial
Bookmarks Related papers MentionsView impact
Characterization of the in vacuo viscoelastic material properties of porous foams used in vehicles
Bookmarks Related papers MentionsView impact
This thesis concerns the modelling of acoustical and vibrational properties of open cell porous f... more This thesis concerns the modelling of acoustical and vibrational properties of open cell porous foams in multi-layered structures, especially multi-layered panels. The object is to enable optimisation of the microscopic geometry of the foam with respect to macroscopic quantities such as sound pressure level, surface velocity, total mass or cost. The developed method is based on numerical solutions to Biot's equations were scaling laws has been used to connect the microscopic geometry of the foam to macroscopic properties such as density, flow resistivity and characteristic length. Efforts have also been made to establish a scaling law for tortuosity that allows for adaptation to different strut shapes.
Bookmarks Related papers MentionsView impact
hp-extension study of a 3d hierarchical fe formulation of biot's equation for isotropic elast... more hp-extension study of a 3d hierarchical fe formulation of biot's equation for isotropic elasto-acoustic porous media
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
For an accurate prediction of the low and medium frequency surface vibration and sound radiation ... more For an accurate prediction of the low and medium frequency surface vibration and sound radiation behaviour of porous materials, there is a need to improve the means of estimating their elastic and acoustic properties. The underlying reasons for this are many and of varying origin, one prominent being a poor knowledge of the geometric anisotropy of the cell microstructure in the manufactured porous materials. Another one being, the characteristic feature of such materials i.e. that their density, elasticity and dissipative properties are highly dependent upon the manufacturing process techniques and settings used. In the case of free form moulding, the geometry of the cells and the dimensions of the struts are influenced by the rise and injection flow directions and also by the effect of gravity, elongating the cells. In addition the influence of the boundaries of the mould also introduces variations in the properties of the foam block produced. Despite these complications, the need to predict and, in the end, optimise the acoustic performance of these materials, either as isolated components or as part of a multi-layer arrangement, is growing. It is driven by the increasing demands for an acoustic performance in balance with the costs, a focus which serves to increase the need for modelling their behaviour in general and the above mentioned, inherent, anisotropy in particular. The current work is focussing on the experimental part of the characterisation of the material properties which is needed in order to correctly represent the anisotropy in numerical simulation models. Then an hybrid approach based on a combination of experimental deformation, strain field mapping, flow resistivity measurement and physically based porous material acoustic Finite Element (FE) simulation modelling is described. This inverse estimation linked with high quality measurements is crucial for the determination of the anisotropic coefficients of the porous materials is illustrated here for soft foam and fibrous wool materials.
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
For an accurate prediction of the low and medium frequency surface vibration and sound radiation ... more For an accurate prediction of the low and medium frequency surface vibration and sound radiation behaviour of porous materials, there is a need to improve the means of estimating their elastic and acoustic properties. The underlying reasons for this are many and of varying origin, one prominent being a poor knowledge of the geometric anisotropy of the cell microstructure in the manufactured porous materials. Another one being, the characteristic feature of such materials i.e. that their density, elasticity and dissipative properties are highly dependent upon the manufacturing process techniques and settings used. In the case of free form moulding, the geometry of the cells and the dimensions of the struts are influenced by the rise and injection flow directions and also by the effect of gravity, elongating the cells. In addition the influence of the boundaries of the mould also introduces variations in the properties of the foam block produced. Despite these complications, the need to predict and, in the end, optimise the acoustic performance of these materials, either as isolated components or as part of a multi-layer arrangement, is growing. It is driven by the increasing demands for an acoustic performance in balance with the costs, a focus which serves to increase the need for modelling their behaviour in general and the above mentioned, inherent, anisotropy in particular. The current work is focussing on the experimental part of the characterisation of the material properties which is needed in order to correctly represent the anisotropy in numerical simulation models. Then an hybrid approach based on a combination of experimental deformation, strain field mapping, flow resistivity measurement and physically based porous material acoustic Finite Element (FE) simulation modelling is described. This inverse estimation linked with high quality measurements is crucial for the determination of the anisotropic coefficients of the porous materials is illustrated here for soft foam and fibrous wool materials.
Bookmarks Related papers MentionsView impact
The flow resistivity tensor, which is the inverse of the viscous permeability tensor, is one of t... more The flow resistivity tensor, which is the inverse of the viscous permeability tensor, is one of the most important material properties for the acoustic performance of open cell foams, used in acoustic treatments. Due to the manufacturing processes, these foams are most often geometrically anisotropic. This paper discusses the estimation of the flow resistivity tensor using an improvement of a previously published method by Göransson, Guastavino et al. First, flow measurements were performed for different orientations of a cubic porous sample. The modelling of the flow resistivity tensor is centred around a three-dimensional Darcy's law model in COMSOL Earth Science Module, representing the experimental set up. The simulations are performed within an optimisation loop, to determine which flow resistivity tensor gives the best fit of the simulation results to the experimental data, of volume flow and pressure drop between the inlets and outlets. The discussion focuses on the optim...
Bookmarks Related papers MentionsView impact
The air flow resistivity of nine adjacent glass wool samples is measured and estimated using a pr... more The air flow resistivity of nine adjacent glass wool samples is measured and estimated using a previously published method. The samples were extracted from a large slab of glass wool material. Identifying the full flow resistivity tensors for nine adjacent cubic glass wool samples allowed for an estimation of the spatial distribution of normal and planar flow resistivity throughout the measured area. The average density of the samples tested is 27.8 kg/m 3 . In addition, the estimated flow resistivity tensors are validated by comparing the estimated flow resistivity tensors with uni-directional measurements on cylindrical samples extracted from the cubic samples tested. Furthermore, the standard measurement method was studied, providing useful insights on the effect of the sample thickness on the measured flow resistivity for an anisotropic material.
Bookmarks Related papers MentionsView impact
Computer Methods in Applied Mechanics and Engineering, 2012
Bookmarks Related papers MentionsView impact
The Journal of the Acoustical Society of America, 2014
Viscoelastic properties of porous materials, typical of those used in vehicles for noise insulati... more Viscoelastic properties of porous materials, typical of those used in vehicles for noise insulation and absorption, are estimated from measurements and inverse finite element procedures. The measurements are taken in a near vacuum and cover a broad frequency range: 20 Hz to 1 kHz. The almost cubic test samples were made of 25 mm foam covered by a "heavy layer" of rubber. They were mounted in a vacuum chamber on an aluminum table, which was excited in the vertical and horizontal directions with a shaker. Three kinds of response are measured allowing complete estimates of the viscoelastic moduli for isotropic materials and also providing some information on the degree of material anisotropicity. First, frequency independent properties are estimated, where dissipation is described by constant loss factors. Then, fractional derivative models that capture the variation with frequency of the stiffness and damping are adapted. The measurement setup is essentially two-dimensional and calculations are three-dimensional and for a state of plane strain. The good agreement between measured and calculated response provides some confidence in the presented procedures. If, however, the material model cannot fit the measurements well, the inverse procedure yields a certain degree of arbitrariness to the parameter estimation.
Bookmarks Related papers MentionsView impact
Journal of Sound and Vibration, 2005
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
The flow resistivity tensor, which is the inverse of the viscous permeability tensor, is one of t... more The flow resistivity tensor, which is the inverse of the viscous permeability tensor, is one of the most important material properties for the acoustic performance of open cell foams, used in acoustic treatments. Due to the manufacturing processes, these foams are most often geometrically anisotropic. This paper discusses the estimation of the flow resistivity tensor using an improvement of a previously published method by Göransson, Guastavino et al. First, flow measurements were performed for different orientations of a cubic porous sample. The modelling of the flow resistivity tensor is centred around a three-dimensional Darcy's law model in COMSOL Earth Science Module, representing the experimental set up. The simulations are performed within an optimisation loop, to determine which flow resistivity tensor gives the best fit of the simulation results to the experimental data, of volume flow and pressure drop between the inlets and outlets. The discussion focuses on the optim...
Bookmarks Related papers MentionsView impact
The air flow resistivity of nine adjacent glass wool samples is measured and estimated using a pr... more The air flow resistivity of nine adjacent glass wool samples is measured and estimated using a previously published method. The samples were extracted from a large slab of glass wool material. Identifying the full flow resistivity tensors for nine adjacent cubic glass wool samples allowed for an estimation of the spatial distribution of normal and planar flow resistivity throughout the measured area. The average density of the samples tested is 27.8 kg/m 3 . In addition, the estimated flow resistivity tensors are validated by comparing the estimated flow resistivity tensors with uni-directional measurements on cylindrical samples extracted from the cubic samples tested. Furthermore, the standard measurement method was studied, providing useful insights on the effect of the sample thickness on the measured flow resistivity for an anisotropic material.
Bookmarks Related papers MentionsView impact