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  • 1.
    Alberdi-Muniain, Ane
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Magneto-sensitive elastomers in vibration isolation2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Vibration isolators made of rubber are used in numerous engineeringapplications to isolate structures from undesirable effects of vibrations.However, once a vibration isolator is installed in an application, it is not possible to modify its characteristics to adjust to changing conditions. An alternative to obtain more adaptive characteristics is touse magneto-sensitive (MS) elastomers. MS elastomers are a type of smart material consisting of an elastomer matrix, such as natural or synthetic rubber, to which iron particles are added displaying properties that vary rapidly, continuously and reversibly by applying an external magnetic field.The aim of this thesis is to investigate the possibility to use MS natural rubber in vibration isolation.Firstly, dynamic shear properties of MS natural rubber are experimentally studied at various frequencies, dynamic amplitudes and magnetic fields. In addition, the influence on the dynamic properties of adding carbon black and plasticisers to MS rubber is investigated. Carbon black is the most popular reinforcing filler that rubber usually contains in engineering applications to improve mechanical properties where as plasticisers simplify the filler blending process.Furthermore, the effectiveness of MS rubber applied in a vibration isolation system is experimentally investigated by measuring the energy flow into the foundation. The energy flow, including both force and velocity of the foundation, is a suitable measure of the effectiveness of a real vibration isolation system where the foundation is not perfectly rigid. The vibration isolation system in this study consists of a solid aluminium mass excitedby an electro-dynamic shaker and mounted upon four nonlinear frequency,amplitude and magnetic field dependent MS isolators being connected to a relatively stiff foundation. The energy flow through the MS isolators is directly measured by inserting a force transducer below each isolator andan accelerometer on the foundation close to each isolator. MS isolators are shown to be more useful than conventional rubber isolators since the dynamic stiffness varies with the application of an external magnetic field,thus resulting in more effective vibration isolation. In addition, the indirect technique is employed to measure the energy flow while requiring only accelerometers since it is usually difficult to directly measure the force in a real application. The indirect technique is validated by direct measurements.Finally, a model of the energy flow through the nonlinear frequency,amplitude and magnetic field dependent MS isolators is developed for the tested vibration isolation system. Vibration isolators are usually only a small connecting component within a more complex system. Hence, simple discrete models are frequently used to characterise the frequency and dynamic amplitude dependence of rubber. Recently, a model of this type has been modified to include magneto-sensitivity and thus model MS rubber. In this study, this novel MS rubber model is incorporated into the full system to model the MS isolators while the foundation is characterised by its driving-point and transfer inertances at and between the connection points.The energy flow model results are compared to those of measurements,showing good agreement. The developed energy flow model provides a basis to design vibration isolator systems made of MS isolators.

  • 2.
    Alberdi-Muniain, Ane
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Gil-Negrete, N.
    Department of Applied Mechanics, CEIT and Tecnun (University of Navarra).
    Kari, Leif
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Direct energy flow measurement in magneto-sensitive vibration isolator systems2012In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 331, no 9, p. 1994-2006Article in journal (Refereed)
    Abstract [en]

    The effectiveness of highly nonlinear, frequency, amplitude and magnetic field dependent magneto-sensitive natural rubber components applied in a vibration isolation system is experimentally investigated by measuring the energy flow into the foundation. The energy flow, including both force and velocity of the foundation, is a suitable measure of the effectiveness of a real vibration isolation system where the foundation is not perfectly rigid. The vibration isolation system in this study consists of a solid aluminium mass supported on four magneto-sensitive rubber components and is excited by an electro-dynamic shaker while applying various excitation signals, amplitudes and positions in the frequency range of 20-200 Hz and using magneto-sensitive components at zero-field and at magnetic saturation. The energy flow through the magneto-sensitive rubber isolators is directly measured by inserting a force transducer below each isolator and an accelerometer on the foundation close to each isolator. This investigation provides novel practical insights into the potential of using magneto-sensitive material isolators in noise and vibration control, including their advantages compared to traditional vibration isolators. Finally, nonlinear features of magneto-sensitive components are experimentally verified.

  • 3.
    Alberdi-Muniain, Ane
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Gil-Negrete, N
    Kari, Leif
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Indirect energy flow measurement in magneto-sensitive vibration isolator systems2013In: Applied Acoustics, ISSN 0003-682x, ISSN 0003-682x, Vol. 74, no 4, p. 575-584Article in journal (Other academic)
    Abstract [en]

    The indirect energy flow measurement method is extended to cover highly nonlinear, frequency, amplitude and magnetic field dependent magneto-sensitive natural rubber isolators applied in a real vibration isolation system. Energy flow is an effective measure of vibration isolation while being a single quantity that considers both force and velocity. The use of the indirect technique is of interest while requiring only accelerometers since it is usually difficult to directly measure the force in a real application. The vibration isolation system is composed of four magneto-sensitive rubber isolators that are inserted under a vibrating source consisting of a solid aluminium mass excited by an electro-dynamic shaker. Magneto-sensitive rubber isolators are more useful than conventional rubber isolators since the dynamic stiffness varies with the application of an external magnetic field, thus resulting in more effective vibration isolation. Various approximations regarding the indirect technique are investigated, concluding that average stiffness of magneto-sensitive isolators can be used and auto-spectrum of the foundation velocity ignored. In addition, various error analyses are performed. Finally, the indirect measurement of the energy flow is validated by direct measurements, showing very good agreement.

  • 4.
    Alberdi-Muniain, Ane
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Gil-Negrete, N.
    Department of Applied Mechanics, CEIT and Tecnun (University of Navarra).
    Kari, Leif
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Influence of carbon black and plasticisers on dynamic properties of isotropic magnetosensitive natural rubber2012In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 41, no 7, p. 310-317Article in journal (Refereed)
    Abstract [en]

    The dynamic shear modulus of magnetosensitive (MS) natural rubber composites is experimentallystudied, where influences of carbon black, plasticiser and iron particle concentrations areinvestigated at various dynamic shear strain amplitudes and external magnetic fields within thelower structure borne frequency range. The iron particles embedded in natural rubber areirregularly shaped and randomly distributed; the plasticisers simplify the iron particle blendingprocess, while carbon black reduces the production costs and improves the mechanicalproperties. The results show that the relative MS effect on the shear modulus magnitude increaseswith increased plasticiser and iron particle concentration and decreases with increased carbonblack concentration. Furthermore, their relative contributions are quantified. Consequently, thestudy provides a basis for optimising the composition of MS natural rubber to meet a variety ofrequirements, including those of vibration isolation, a promising application area for MS materials.

  • 5.
    Alberdi-Muniain, Ane
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Gil-Negrete, N
    Kari, Leif
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Modelling energy flow through magneto-sensitive vibration isolators2013In: International Journal of Engineering Science, ISSN 0020-7225, E-ISSN 1879-2197, Vol. 65, p. 22-39Article in journal (Refereed)
    Abstract [en]

    A highly nonlinear model of the energy flow in a magneto-sensitive (MS) vibration isolation system is developed where it is possible to investigate the influences of MS rubber material parameters; magnetic field strength; MS isolator dimension and position; excitation force magnitude, position and frequency; engine mass, inertia and dimension and, finally, foundation inertance. The MS vibration isolation system consists of an engine modelled by a solid mass, excited by a vertical force and mounted upon four MS isolators being connected to a relatively stiff foundation characterised by its driving-point and transfer inertances at and between the connection points. The energy flow into the foundation is the most appropriate indicator of the effectiveness of a real vibration isolation system while considering both foundation velocity and force. The MS isolator model applied is a nonlinear MS rubber model including frequency, dynamic amplitude and magnetic field dependence. The energy flow model results are compared to those of measurements, showing good agreement. Finally, parameter studies are carried out. The developed energy flow model provides a basis for designing MS vibration isolation systems to meet specific requirements.

  • 6.
    Alberdi-Muniain, Ane
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Gil-Negrete, N.
    Department of Applied Mechanics, CEIT and Tecnun (University of Navarra).
    Nieto, F.J.
    Department of Applied Mechanics, CEIT and Tecnun (University of Navarra).
    Kari, Leif
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Vinolas, J.
    Department of Applied Mechanics, CEIT and Tecnun (University of Navarra).
    An experimental study of magneto-sensitive natural rubber components applied in a vibration isolation system2009In: CONSTITUTIVE MODELS FOR RUBBER VI / [ed] Gert Heinrich, Michael Kaliske, Alexander Lion, London: Taylor & Francis, 2009, p. 99-104Conference paper (Refereed)
    Abstract [en]

    The effectiveness of magneto-sensitive natural rubber components applied in a vibration isolation system is experimentally investigated, where influences of excitation position, amplitude, frequency and magnetic field are examined. The magneto-sensitive elastomer consists of micron-sized, irregularly shaped iron particles blended in soft natural rubber at a concentration close to the critical particle volume fraction, shown to be the most favorable composition for optimum behaviour. A rigid aluminium mass supported on four vibration isolators is excited by an electro-dynamic shaker. Each component of this vibration isolation system is composed of two thin, square shaped, symmetrically positioned magneto-sensitive elements excited in simple shear with a magnetic field applied perpendicularly to the motion by an electromagnet. The magnetic field is varied by applying different intensities through the coil. The excitation position is either on the centre or on the edge of the surface of the mass, using step-sine excitation of various amplitudes in the frequency range of 0 to 300 Hz. The results show that it is possible to use magneto-sensitive rubber for vibration control purposes.

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