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Structure-borne sound properties of isotropic magneto-rheological rubber
KTH, Superseded Departments, Vehicle Engineering.ORCID iD: 0000-0001-5760-3919
KTH, Superseded Departments, Fibre and Polymer Technology.
KTH, Superseded Departments, Fibre and Polymer Technology.
2002 (English)In: Kautschuk und Gummi, Kunststoffe, ISSN 0022-9520, Vol. 55, no 12, 669-673 p.Article in journal (Refereed) Published
Abstract [en]

The dynamic properties of isotropic magneto-rheological rubber are examined through experiments within an audible frequency range covering 100 to 1250 Hz while applying an external magnetic field of 0 to 0.8 T. The shear modulus for this manufacturer convenient material, consisting of dispersed irregular, micrometer sized iron particles in a nitrile rubber matrix, is found to depend strongly on both frequency and magnetic field, while the loss factor is almost independent of those factors. Magneto-rheological rubbers applied to vibration isolators promise to have more functionality than conventional isolators while rapidly and reversibly change rigid body and stiffness peak frequencies.

Place, publisher, year, edition, pages
2002. Vol. 55, no 12, 669-673 p.
Keyword [en]
magneto-rheology, isotropy, iron particle, shear modulus, loss factor, magnetic field
National Category
Applied Mechanics
URN: urn:nbn:se:kth:diva-5334ISI: 000179899900007OAI: diva2:8855
NR 20140805Available from: 2004-10-01 Created: 2004-10-01 Last updated: 2012-02-11Bibliographically approved
In thesis
1. Performance of Magnetorheological Rubber Materials
Open this publication in new window or tab >>Performance of Magnetorheological Rubber Materials
2004 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Magnetorheological (MR) rubber materials are the solid analogue of magnetorheological fluids; i.e. their rheological properties can be controlled continously, rapidly, and reversibly by an applied magnetic field. They consist of magnetically polarisable particles in an elastomer matrix and they can be made to respond to changes in their environment; hence, they are considered as "smart" materials. Examples of potential applications for these materials are adaptive tuned vibration absorbers, stiffness-tuneable mounts and suspensions, and automotive bushings.

The purpose of this work was to increase the knowledge relating to magnetorheological materials for damping applications. The materials should exhibit a large response to an applied magnetic field, and have good mechanical and long-term properties.

MR rubber materials were made from nitrile, natural and silicone rubber, with irregularly shaped iron particles several micrometres in size. The particles were not aligned by a magnetic field prior to the vulcanisation; hence, the materials can be considered to be isotropic. These materials show a large MR effect, i.e. an increase in the shear modulus when a magnetic field is applied, although the particles are not aligned within the material. This is explained by the low critical particle volume concentration (CPVC) of such particles. Similar behaviour can be obtained with materials containing carbonyl iron, if the particles are aggregated so that they behave like large irregular particles. The iron particle concentration must be very close to the CPVC in order to obtain a large MR effect without alignment of the particles.

The absolute MR effect (MPa) in an isotropic MR rubber material with large irregular iron particles is independent of the matrix material, and the relative MR effect (%) can thus be increased by the addition of plasticisers. However, the obtainable effect is limited by the reinforcement of the particles and by friction between the particles. Therefore, it is very difficult, if not impossible, to achieve an MR effect larger than 60%.

Other ways of increasing the MR effect are to increase the strength of the magnetic field, although the materials saturate magnetically at high field strengths, or to use small strain amplitudes. The strong strain amplitude dependence of the MR effect suggests that MR rubber materials are most suitable for low amplitude applications, such as sound and vibration insulation. Measurements at frequencies within the audible frequency range show that this is a promising application for MR rubber materials.

The incorporation of large amounts of iron into the rubber matrix decreases the oxidative stability dramatically. This is probably due to iron oxides on the surface of the particles, and to the fact that the oxidation rate is enhanced by iron ions, which are able to diffuse into the matrix. Standard antioxidants do not provide sufficient stabilisation for MR rubbers. Thus, proper stabilisation systems have to be found in order for these materials to be successful in applications.

Place, publisher, year, edition, pages
Stockholm: Fiber- och polymerteknologi, 2004
Trita-FPT-Report, ISSN 1652-2443 ; 2004:32
Materials science, magnetorheological rubber, Materialvetenskap
National Category
Materials Engineering
urn:nbn:se:kth:diva-31 (URN)91-7283-856-6 (ISBN)
Public defence
2004-10-01, K2, KTH, Teknikringen 28, Stockholm, 10:00
Available from: 2004-10-01 Created: 2004-10-01 Last updated: 2012-03-22

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