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  • 1. Deckers, E.
    et al.
    Vandepitte, D.
    Desmet, W.
    Hörlin, Nils Erik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    A novel wave based prediction technique for the efficient dynamic modelling of poro-elastic materials2009In: 8th European Conference on Noise Control 2009, EURONOISE 2009 - Proceedings of the Institute of Acoustics, 2009, no PART 3Conference paper (Refereed)
    Abstract [en]

    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 validation calculations.

  • 2. Deckers, Elke
    et al.
    Hörlin, Nils-Erik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Vandepitte, Dirk
    Desmet, Wim
    A Wave Based Method for the efficient solution of the 2D poroelastic Biot equations2012In: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, E-ISSN 1879-2138, Vol. 201, p. 245-262Article in journal (Refereed)
    Abstract [en]

    The vibro-acoustic behaviour of poroelastic materials is often formulated as boundary value problems based on the continuum mechanics Blot's theory expressed as two coupled partial differential equations. This paper presents an extension of the Wave Based Method (WBM), a numerical technique to solve these vibro-acoustic boundary value problems in a computationally efficient manner. At present, the Finite Element Method (FEM) is the most commonly used prediction technique to deal with these Biot equations, but suffers from the disadvantage that the system matrices have to be recalculated for each frequency of interest due to the frequency-dependent equation parameters. This harms the inherent effectiveness of the FEM. Additionally, due to the discretisation into a large number of small finite elements and the high number of unknowns per node, the computational efforts involved practically restrict the use of FEM to low-frequency applications. The method discussed in this paper is based on an indirect Trefftz approach. Exact solutions of the three coupled waves, supported by Biot's equations, are used as basis functions in a solution expansion to approximate the field variables in a poroelastic boundary value problem. This approach leads to smaller systems of equations, enabling an efficient solution at higher frequencies.

  • 3.
    Finnveden, Svante
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Hörlin, Nils-Erik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Barbagallo, Mathias
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Characterization of the in vacuo viscoelastic material properties of porous foams used in vehiclesArticle in journal (Other academic)
  • 4.
    Finnveden, Svante
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Hörlin, Nils-Erik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Barbagallo, Mathias
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Dynamic characterization of viscoelastic porous foams used in vehicles based on an inverse finite element method2014In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 135, no 4, p. 1834-1843Article in journal (Refereed)
    Abstract [en]

    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 25mm 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.

  • 5.
    Guastavino, Remi
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Hörlin, Nils-Erik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Characterisation of anisotropic porous foam materials2005Conference paper (Other academic)
  • 6.
    Guastavino, Rémi
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Hörlin, Nils-Erik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    A 3D anisotropic flow resistivity estimation for soft porous foam2008Report (Other academic)
  • 7.
    Göransson, Peter
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Guastavino, Remi
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Hörlin, Nils-Erik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Measurement and inverse estimation of 3D anisotropic flow resistivity for porous materials2009In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 327, no 3-5, p. 354-367Article in journal (Refereed)
    Abstract [en]

    This paper presents a new methodology for estimating the anisotropic flow resistivity for porous materials. From pressure measurements on a cubic or parallelepiped sample of a porous material, the flow resistivities are determined using inverse estimation. The core of the estimation is a series of 3D solutions to Darcy's law, where the flow resistivity tensor is varied until the sum of the quadratic errors between measured and computed pressures is minimised. The overall approach and experimental set-up used, enabling efficient measurements of high quality, are described in some detail together with the main steps of the measurement and estimation procedures. Results from a fibrous glass wool and a polyurethane foam are discussed and compared to standard measurement data.

  • 8.
    Göransson, Peter
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Guastavino, Rémi
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Hörlin, Nils-Erik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    A 3D anisotropic flow resistivity measurement method for fibrous wool materials2008Report (Other academic)
  • 9.
    Göransson, Peter
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Hörlin, Nils-Erik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Anisotropic porous materials, and then?2008Conference paper (Other academic)
  • 10.
    Göransson, Peter
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Hörlin, Nils-Erik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Vibro-acoustic modelling of anisotropic porous elastic materials: A preliminary study of the influence of anisotropy on the predicted performancein a multi-layer arrangement.2010In: Acta Acoustica united with Acustica, ISSN 1610-1928, E-ISSN 1861-9959, Vol. 96, p. 258-265Article in journal (Refereed)
    Abstract [en]

    During the recent years considerable efforts have been spent on developing numerical models and performing the necessary characterisation of elastic, dynamic and acoustic properties of porous materials. Originally having been considered to be isotropic, such materials have lately also been studied in terms of their anisotropic properties. In this paper, the influence of anisotropy on the vibroacoustic performance is illustrated and evaluated for a multi-layer configuration with varying boundary conditions between the porous material and a solid plate. The paper starts with a brief review of a recently published anisotropic, mixed displacement pressure weak formulation with a particular emphasis on the anisotropic properties. Using the material properties for a hypothetical porous foam model, the predicted response is evaluated. The influence of anisotropy is found to be significant in terms of response amplitude and apparent damping. For some boundary conditions the predicted response is an order of magnitude lower for the anisotropic material model, in particular for frequency ranges where the dynamics of the foam are significant.

  • 11.
    Göransson, Peter
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Hörlin, Nils-Erik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Semeniuk, Bradley
    Rieter Automotive Managment AG, Switzerland].
    Influence of surface porosity on the radiated sound from multilayer automotive trim components2005In: SAE 2005 Noise and Vibration Conference and Exhibition, May 2005, 2005Conference paper (Refereed)
    Abstract [en]

    Lightweight porous automotive acoustic multilayer trim components have been traditionally specified in terms of sound absorption and sound transmission loss performance targets. These targets are valid for airborne noise excitation only, in the medium to high frequency ranges. Unfortunately, this neglects the fact that in real-world vehicle applications, these components are also subjected to low-medium frequency structural vibration inputs from the mechanical components of the vehicle, which is typically an acoustic sound radiation problem.

  • 12.
    Hörlin, Nils-Erik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    3D hierarchical hp-FEM applied to elasto-acoustic modelling of layered porous media2005In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 285, no 1-2, p. 341-363Article in journal (Refereed)
    Abstract [en]

    This paper presents a 3-D hierarchical (p-version) finite element description of the solid displacement-fluid displacement form of Biot's equation for elasto-acoustic modelling of multiple-layered isotropic porous media. The convergence related to mesh refinement extensions for different orders of polynomial approximation is briefly discussed for a homogeneous foam. The highest computational efficiency for reasonable levels of the error in the low-frequency region was obtained for fourth-order polynomial finite element interpolations. The main focus is on coupling conditions and on the convergence of solutions to Biot's equations in cases with multiple layers having different material properties. Simulations of a two-layered porous material with low flow resistivity suggest slow convergence rate of the fluid displacement field close to the interface between the layers.

  • 13.
    Hörlin, Nils-Erik
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    A comparative study of three different weak formulations of biot's equations for elasto-acoustic wave propagation in layered poroelastic media using p-version finite elements2004Article in journal (Other academic)
  • 14.
    Hörlin, Nils-Erik
    KTH, Superseded Departments, Vehicle Engineering.
    A study of hierarchical FE solutions of Biot's equations for acoustic modeing of poroelastic medial2001Licentiate thesis, comprehensive summary (Other scientific)
  • 15.
    Hörlin, Nils-Erik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    A symmetric weak form of Biot's equations based on redundant variables representing the fluid, using a Helmholtz decomposition of the fluid displacement vector field2010In: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, E-ISSN 1097-0207, Vol. 84, no 13, p. 1613-1637Article in journal (Refereed)
    Abstract [en]

    A novel symmetric weak formulation of Biot's equations for linear acoustic wave propagation in layered poroelastic media is presented. The primary variables used are the frame displacement, the acoustic pore pressure, the scalar potential and the vector potential obtained from a Helmholtz decomposition of the fluid displacement. Also a symmetric weak form based on the frame displacement, the pore pressure and the fluid displacement is obtained as an intermediate result. hp finite element simulations of a double leaf partition based on this new weak formulation is verified against simulation results from the classical frame displacement, fluid displacement formulation and a frame displacement pore pressure formulation. All three formulations simulated, displays the same rate of convergence with respect to finite element bases polynomial degree. The novel formulation also extends a previously published frame displacement, pore pressure, scalar fluid displacement potential formulation with an implicit irrotational fluid displacement assumption to a full representation of Biot's equations.

  • 16.
    Hörlin, Nils-Erik
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Hierarchical finite element modelling of Biot's equations for vibro-acoustic modelling of layered poroelastic media2004Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis concerns three-dimensional finite element modelling of Biot's equations for elasto-acoustic modelling of wave propagation in layered media including porous elastic materials. The concept of hierarchical (p-version) finite elements are combined with various weak forms of Biot's equations. Computationally efficient methods providing accurate solutions of sound propagation in layered porous media are discussed. The research falls within the areas linear acoustics and numerical acoustics. Important applications of the developed methods may be found within vehicle interior acoustics, e.g. engineering design of damping treatment based on multiple layers of porous materials.

  • 17.
    Hörlin, Nils-Erik
    KTH, Superseded Departments, Vehicle Engineering.
    hp-extension study of a 3d hierarchical fe formulation of biot's equation for isotropic elasto-acoustic porous mediaManuscript (preprint) (Other academic)
  • 18.
    Hörlin, Nils-Erik
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Weak, anisotropic symmetric formulations of Biot's equations for vibro-acoustic modelling of porous elastic materials2010In: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, E-ISSN 1097-0207, Vol. 84, no 12, p. 1519-1540Article in journal (Refereed)
    Abstract [en]

    In this paper a fully anisotropic symmetric weak formulation of Biot's equations for vibro-acoustic modelling of porous elastic materials in the frequency domain is proposed. Starting from Biot's equations in their anisotropic form, a mixed displacement-pressure formulation is discussed in terms of Cartesian tensors. The anisotropic equation parameters appearing in the differential equations are derived from material parameters which are possible to determine through experimental testing or micro-structural simulations of the fluid and the porous skeleton. Solutions are obtained by applying the finite element method to the proposed weak form and the results are verified against a weak displacement-based formulation for a foam and plate combination.

  • 19.
    Hörlin, Nils-Erik
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Guastavino, Remi
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Finite element modelling of multi-layered trim components: possibilities and difficulties2005Conference paper (Other academic)
  • 20.
    Hörlin, Nils-Erik
    et al.
    KTH, Superseded Departments, Vehicle Engineering.
    Nordström, M.
    KTH, Superseded Departments, Vehicle Engineering.
    Göransson, Peter
    KTH, Superseded Departments, Vehicle Engineering.
    A 3-D hierarchical Fe formulation of Biot's equations for elasto-acoustic modelling of porous media2001In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 245, no 4, p. 633-652Article in journal (Refereed)
    Abstract [en]

    A three-dimensional hierarchical finite element formulation of Biot's equation for low frequency elasto-acoustic wave propagation in fluid saturated porous media based on a weak formulation with fluid displacement and solid displacement as dependent variables is presented. A global error measure for evaluation of the convergence is proposed. Numerical simulations of an air saturated polyurethane foam material show faster convergence for the hierarchical extensions than for linear and quadratic serendipity finite element mesh refinement extensions.

  • 21.
    Lind, Eleonora
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Hörlin, Nils-Erik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Evaluation of tortuosity models for open porous foams2008Article in journal (Other academic)
  • 22.
    Lindberg, Eskil
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Hörlin, Nils-Erik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    An Experimental Study of Interior Vehicle Roughness Noise from Disc Brake Systems2011Manuscript (preprint) (Other academic)
  • 23.
    Lindberg, Eskil
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Hörlin, Nils-Erik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    An experimental study of interior vehicle roughness noise from disc brake systems2013In: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 74, no 3, p. 396-406Article in journal (Refereed)
    Abstract [en]

    An experimental study of the friction-induced noise generated by the disc brake system of a passenger car is presented. In particular, the brake noise usually referred to as wire brush or roughness noise is studied. This is, in terms of frequency spectral content a broadband phenomenon, resulting from the interaction of multiple asperities in the tribological contact. A new experimental method for measurements of disc brake roughness noise is proposed, and is used in a lab environment where the vehicle speed and the brake pressure are accurately controlled. The aim is to study the influence of vehicle speed and brake pressure on the roughness noise inside the vehicle. It is shown for the specific test case that the transmission from the source to the interior is a vibro-acoustic structure-borne phenomenon. Measurements show that there is a, as expected, strong correlation between increased interior noise and both increased vehicle speed and brake pressure.

  • 24.
    Lindberg, Eskil
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Hörlin, Nils-Erik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Component mode synthesis using undeformed interface coupling modes to connect soft and stiff substructures2013In: Shock and Vibration, ISSN 1070-9622, E-ISSN 1875-9203, Vol. 20, no 1, p. 157-170Article in journal (Refereed)
    Abstract [en]

    Classical component mode synthesis methods for reduction are usually limited by the size and compatibility of the coupling interfaces. A component mode synthesis approach with constrained coupling interfaces is presented for vibro-acoustic modelling. The coupling interfaces are constrained to six displacement degrees of freedom. These degrees of freedom represent rigid interface translations and rotations respectively, retaining an undeformed interface shape. This formulation is proposed for structures with coupling between softer and stiffer substructures in which the displacement is chiefly governed by the stiffer substructure. Such may be the case for the rubber-bushing/linking arm assembly in a vehicle suspension system. The presented approach has the potential to significantly reduce the modelling size of such structures, compared with classical component mode synthesis which would be limited by the modelling size of the interfaces. The approach also eliminates problems of nonconforming meshes in the interfaces since only translation directions, rotation axes and the rotation point need to be common for the coupled substructures. Simulation results show that the approach can be used for modelling of systems that resemble a vehicle suspension. It is shown for a test case that adequate engineering accuracy can be achieved when the stiffness properties of the connecting parts are within the expected range of rubber connected to steel.

  • 25.
    Lindberg, Eskil
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Hörlin, Nils-Erik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Component Mode Synthesis Using Undeformed InterfaceCoupling Modes to Connect Soft and Sti Substructures2011Manuscript (preprint) (Other academic)
  • 26.
    Lindberg, Eskil
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Östberg, Martin
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Hörlin, Nils-Erik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    A vibro-acoustic reduced order model using undeformed coupling interface substructuring - Application to rubber bushing isolation in vehicle suspension systems2014In: Applied Acoustics, ISSN 0003-682x, Vol. 78, p. 43-50Article in journal (Refereed)
    Abstract [en]

    A vibro-acoustic reduced order model (ROM) based on a substructuring method using undeformed coupling interfaces (UCI) is proposed. The method may be used to reduce the order of a global problem, this by subdividing the global system to substructures interacting through UCI's. The local dynamic stiffness of each substructure may then be modelled with a, for that particular problem, best suited description. The feasibility of the method is demonstrated by a sensitivity analysis of the vibro-acoustic power isolation in a vehicle suspension system, comprising of a link arm connected to a vehicle car body through two rubber bushings. The link arm ROM is a component mode synthesis (CMS)-UCI, the rubber bushing model is a UCI-ROM derived from a 2D axisymmetric model using a frequency dependent visco-elastic material model. Finally the car body model is a frequency dependent UCI-ROM from a full car body finite element model. It is shown that the UCI-ROM approach efficiently can be used for parametric studies on a substructure level. The results suggest that the performed reorientation of the rubber bushings can alter, with orders of magnitude, the energy flow into the car.

  • 27.
    Semeniuk, Bradley
    et al.
    Rieter Automotive Managemnet AG, Switzerland.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Hörlin, Nils-Erik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Sound Radiated From Multilayer Trim Components2005In: Forum Acusticum Budapest 2005: 4th European Congress on Acustics, 2005, p. 117-122Conference paper (Refereed)
    Abstract [en]

    Lightweight porous acoustic multilayer trim components have traditionally been specified in terms of sound absorption and sound transmission loss performance targets. These targets are valid for airborne noise excitation only, in the medium to high frequency ranges. Unfortunately, this neglects the fact that in real-world vehicle applications, these components are also subjected to low-medium frequency structural vibration inputs from mechanical components, which is typically an acoustic sound radiation problem. Importantly, the material specification of the trim component developed only for absorption and sound transmission loss may be sub-optimal in terms of sound radiation behaviour. This then highlights the necessity for additional focus on this topic, especially from a numerical simulation perspective in the early stages of the sound proofing development process. The appropriate low-medium-high frequency acoustic performance balance can then be obtained. Simulation methods are now well established for predicting the absorption and sound transmission loss of multilayer trim components including lightweight porous materials and surfaces, but are less well developed for the prediction of the multilayer sound radiation problem.

  • 28.
    Van der Kelen, Christophe
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Hörlin, Nils-Erik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Inverse Estimation of the Flow Resistivity Tensor of Open-Cell Foams from Experimental Data and Darcy’s Flow Simulations2010In: Proceedings of the COMSOL Conference 2010, 2010Conference paper (Other academic)
    Abstract [en]

    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 optimization 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 optimiser, the use of COMSOL Multiphysics and the identified flow resistivity tensor of a Melamine sample.

  • 29.
    Van der Kelen, Christophe
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Hörlin, Nils-Erik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Measurement and Inverse Estimation of the Full Anisotropic Flow Resistivity Tensor of Glass Wool2010Report (Other academic)
    Abstract [en]

    The air flow resistivity of nine adjacent glass wool samples is measured and estimated using a previously published method. The samples are extracted from a large slab of glass wool material. Identifying the full flow resistivity tensors for nine adjacent cubic glass wool samples allows for an estimation of the spatial distribution of normal and planar flow resistivity throughout the measured material. The average density of the samples tested is 27.8 kg/m3. The estimated flow resistivity tensors are validated by comparison to uni-directional measurements on cylindrical samples, extracted from the cubic glass wool samples tested. Furthermore, the uni-directional measurement method is studied, providing useful insights on the effect of sample thickness on the measured flow resistivity for an anisotropic material.

  • 30.
    Östberg, Martin
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Hörlin, Nils
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Kari, Leif
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Weak forms for modelling of rotationally symmetric, multilayered structures, including anisotropic poro-elastic media2012In: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, E-ISSN 1097-0207, Vol. 90, no 8, p. 1035-1052Article in journal (Refereed)
    Abstract [en]

    A weak form of the anisotropic Biot's equation represented in a cylindrical coordinate system using a spatial Fourier expansion in the circumferential direction is presented. The original three dimensional Cartesian anisotropic weak formulation is rewritten in an arbitrary orthogonal curvilinear basis. Introducing a cylindrical coordinate system and expanding the circumferential wave propagation in terms of orthogonal harmonic functions, the original, geometrically rotationally symmetric three dimensional boundary value problem, is decomposed into independent two-dimensional problems, one for each harmonic function. Using a minimum number of dependent variables, pore pressure and frame displacement, a computationally efficient procedure for vibro-acoustic finite element modelling of rotationally symmetric three-dimensional multilayered structures including anisotropic porous elastic materials is thus obtained. By numerical simulations, this method is compared with, and the correctness is verified against, a full three-dimensional Cartesian coordinate system finite element model.

  • 31.
    Östberg, Martin
    et al.
    KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design. KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Hörlin, Nils-Erik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Weak formulation of Biot's equations in cylindrical coordinates with harmonic expansion in the circumferential direction2010In: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, E-ISSN 1097-0207, Vol. 81, no 11, p. 1439-1454Article in journal (Refereed)
    Abstract [en]

    A weak symmetric form of Biot's equation in cylindrical coordinates with a spatial Fourier expansion in the circumferential direction is presented. The solid phase displacement and the pore pressure are used as the dependent variables. The original three-dimensional boundary value problem is here, due to the orthogonality of the harmonic functions and the rotationally symmetric geometry, decomposed into independent two-dimensional problems, one for each harmonic function. This formulation provides a computationally efficient procedure for vibroacoustic finite element modelling of rotationally symmetric three-dimensional multilayered structures including porous elastic materials. By numerical Simulations, this method is compared with, and verified against, full three-dimensional Cartesian coordinate system finite element models.

1 - 31 of 31
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