• Smart Structures and Systems
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• v.18 no.2
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• pp.233-247
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• 2016

The vibration characteristic analysis of sandwich cylindrical shells subjected with magnetorheological (MR) elastomer and constraining layer are considered in this study. And, the discrete finite element method is adopted to calculate the vibration and damping characteristics of the sandwich cylindrical shell system. The effects of thickness of the MR elastomer, constraining layer, applied magnetic fields on the vibration characteristics of the sandwich shell system are also studied in this paper. Additionally, the rheological properties of the MR elastomer can be changed by applying various magnetic fields and the properties of the MR elastomer are described by complex quantities. The natural frequencies and modal loss factor of the sandwich cylindrical shells are calculated for many designed parameters. The core layer of MR elastomer is found to have significant effects on the damping behavior of the sandwich cylindrical shells.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.92-93
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• 2013

In this study, Shock Absorption performance of Magneto-rheological elastomer(MRE) is identified through the drop impact test. Magneto-rheological materials are divided into two groups by MR fluid in fluid state and MR elastomer in solid state like rubber. The stiffness characteristics of Magneto-rheological material can be changed as magnetic field is applied. The impact loads in MR elastomer were measured under weight of impactor. Experiment results are shown through the experiments to confirm the effect of shock absorption of MR elastomer. Thus, the MR elastomer can be applied to shock absorber used in area that shock occurs.

• Tribology and Lubricants
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• v.27 no.4
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• pp.213-217
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• 2011

In this study, friction characteristics using elastomeric actuator with Magneto-rheological (MR) materials are identified. Typically, Magneto-rheological materials are divided into two groups by MR fluid in fluid state and MR elastomer in solid state like rubber. The stiffness characteristics of Magneto-rheological material can be changed as magnetic field is applied. MR fluid has been applied to various industry fields such as to brake, clutch, damper, engine mount and etc. However, MR fluid has been used under the sealed condition to prevent leaking issues. In order to overcome these problems, MR elastomer that has same property as MR fluid has been developed and studied. MR elastomer mainly consists of polymer material such as natural rubber or silicon rubber with particles that can be polarized with magnetic field. And it is called as a smart material since its stiffness and damping characteristics can be changed. In this study, MR elastomer is produced and pin-on-disc tests are carried out to identify the friction characteristics of the material. Several test conditions are applied to evaluate the feasibility to use as a smart actuator in the field of vibration control.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.8
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• pp.714-719
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• 2011

This paper presents vibration characteristics of magnetorheological(MR) elastomer, whose elastic modulus are controllable by applied magnetic field. By using this property, the material can be applied to vibration absorber, so that the stiffness of the absorber can be changed and actively controlled according to the magnetic flux density. However, the various performances of MR elastomer depends on different polarized direction of particles by applied magnetic field and dimension during the manufacturing process. In this paper, in order to obtain the optimal characteristics of MR elastomer, MR elastomers with different types and dimensions are prepared for a series tests. Using this test setup, extent of natural frequency shifted against magnetic field at various excitation frequencies can be measured. Specimens are prepared with 3 types, as cylinder samples exposed to magnetic field vertically, horizontally and unexposed during cure, respectively. Also, a set of design variables are considered to produce MR elastomers. Through the modal tests of mass structure with MR elastomer, the optimal design as well as the polarization direction of MR elastomer is obtained among the various dimensions and 3 directional types of MR elastomers.

• Tribology and Lubricants
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• v.28 no.6
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• pp.333-339
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• 2012

Typical magneto-rheological (MR) elastomers consist of silicon-based material. A number of studies have been carried out to evaluate the vibration and tribological characteristics of silicon-based MR e-lastomers. However, these elastomers have quite low strength, so they have low wear resistance. In this study, polyurethane-based MR elastomers with performances better than those of MR elastomers. Experiments have been conducted on different MR elastomers (Pu MR elastomer, Pu-Si MR elastomer, and Pu-wrapped-Si MR elastomer) and different predefined magnetic directions (Non-Direction, Vertical Direction, and Horizontal Directionality) to evaluate the friction and wear performance under a magnetic field. The results show that Pu-wrapped-Si MR elastomer with a horizontal predefined magnetic field has the best performance in terms of wear.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.752-757
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• 2011

This paper presents vibration characteristics of magnetorheological (MR) elastomer, whose elastic modulus are controllable by an applied magnetic field. By using this property, the material can be applied to vibration absorber, so that the stiffness of the absorber can be changed and actively controlled according to the magnetic flux density. However, the various performances of MR elastomer depends on different magnetically polarization direction and dimension during the manufacturing process. In this paper, in order to obtain the optimal characteristics of MR elastomer, MR elastomers with different types and dimensions are prepared for a series tests. Using this test setup, extent of natural frequency shifted against magnetic field at various excitation frequencies can be measured. Specimens prepared with 3 types which are exposed to magnetic field vertically, horizontally and unexposed during cure. Also, a set of design variables are considered to produce MR elastomers. Through the modal tests of mass structure with MR elastomer, the optimal design as well as the polarization direction of MR elastomer is obtained among the various dimensions and 3 directional types of MR elastomers.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.1137-1141
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• 2007

This paper is concerned with the experimental research of magnetorheological elastomers (MREs). The modulus of the MR elastomers can be controlled by an applied magnet field, so that it can be effectively used for vibration suppression applications. The MR elastomer in this experiment is a mixture of KE-1300 silicone, carbonyl iron powder (300mesh) and a silicone hardener (CAT-1300). Three specimens were manufactured and tested by using the vibration testing instruments. The magnetic field was generated by the permanent magnets. The experimental results show that the natural frequencies of the test article with MR elastomer changes by the applied magnetic field. The performance of the MR elastomer can be increased by stronger magnetic fields. This is under investigation.

• Tribology and Lubricants
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• v.30 no.4
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• pp.234-239
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• 2014

Magneto-rheological elastomer (MR elastomer) is a smart material, because it has mechanical properties that change under a magnetic field. An MR elastomer changes its stiffness characteristics when the inner particles (iron particles) align along the direction of a magnetic field. There has been much research to make use of this characteristic to control vibration issues in various mechanical systems, such as for mounting systems in the automotive field, home appliances, etc. Furthermore, the friction and wear properties of MR elastomer have been studied, as these relate to the durability of the material needed to meet engineering requirements. Rolling friction (or rolling resistance) is one of these friction properties, but has not yet been studied in the context of MR elastomers. In this study, an MR elastomer is fabricated in the shape of a hollow cylinder to evaluate the rolling friction characteristic under a magnetic field. The test apparatus is setup and a strain gauge is used to calculate the rolling resistance under test conditions. Permanent magnets are used to supply the magnetic field during tests. The load and rolling speed conditions are also considered for the tests. The test results show that rolling friction characteristic has a different trend under different magnetic field, load, and rolling speed conditions. It is assumed that the stiffness change of an MR elastomer under a magnetic field has an effect on the rolling friction characteristic of the MR elastomer. For the future work, the rolling friction characteristics of MR elastomers will be controlled by adjusting the strength of the magnetic field using electromagnets.

• Tribology and Lubricants
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• v.28 no.3
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• pp.107-111
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• 2012

In this study, application feasibility of Magneto-rheological elastomer to friction control is investigated to identify the reciprocating friction and wear performance in applied magnetic field. Friction and wear of MR elastomerare measured by reciprocating tester by controlling the magnetic field. In the case of applied magnetic field, the coefficient of friction increases as both load and velocity increase. For the case of no magnetic field, the value of coefficient of friction hardly changes during the test. The amount of destruction is measured through cross section images of MR elastomer after tests. The depths of destruction are compared for MR elastomer with or without magnetic field. The results show that the depth of destruction of MR elastomer with magnetic field is deeper than without magnetic field. Based on the obtained results, optimal braking and driving performance can be achieved by controlling the coefficient of friction of MR elastomer, which can be applied to various industrial applications such as driving systems of automobiles and robots.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.6
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• pp.582-587
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• 2012

This paper presents a solution of the vibration reduction in the hollow shafts by using magentorehological( MR) elastomer. Proposed active damping structure is built by embedding the MR elastomers whose elastic modulus is controllable by an applied magnetic field. MR elastomers consist of synthetic rubber filled with micron-sized magnetizable particles. For reduction of vibration, dynamic damper of hollow shaft is designed by using MR elastomer and equipped in the hollow shaft for the application to drive shaft. Experiment results are shown through the experiments to confirm the effect of MR elastomer dynamic damper for vibration reduction. Thus, the designed damping structure can be applied to vibration absorber used in drive shafts as well as the propeller shafts.