Proceedings of the ASME 2009 Conference on Smart Materials, Adaptive Structures and Intelligent Systems
SMASIS2009
September 20-24, 2009, Oxnard, California, USA
SMASIS2009- 1310
DEFINING AND INVESTIGATING NEW SYMMETRY CLASSES FOR THE NEXT
GENERATION OF MAGNETORHEOLOGICAL ELASTOMERS
Paris R. von Lockette, Rowan University
Samuel Lofland, Rowan University
Joseph Biggs, Rowan University
1
Copyright © 2009 by ASME
ABSTRACT
This work addresses the fundamental difference in behavior
between magnetorheological elastomers (MREs) formed from
soft-magnetic particles, whose behavior is driven by local
demagnetizing effects and those formed with hard-magnetic
particles that have a preferred magnetic axis and therefore
generate magnetic torques at the particle level. This work
explores the phenomena by defining and examining four
classes of MREs based upon permutations of particle alignment
- magnetization pairs , i.e. I-I for magnetically isotropic
particles arranged isotropically (randomly, or unaligned), A-A
for magnetically anisotropic particles arranged anisotropically
(typically aligned in chains), etc. The distinctions are important
since the particle-field interactions for each class differ
substantially. The behavior of classes I-I and I-A are driven
primarily by demagnetizing effects while classes I-A and A-A
are driven by the torques produced in the particles.MRE
materials made with barium hexaferrite (BaM) (Classes A-A
and I-A) and Fe powders (Classes A-I and I-I), aligned and
unaligned, served as proxies for each of the four classes in this
work. BaM, with saturation magnetization Msat = 4 × 105 A/m
and coercive field Hc > 3 × 105 A/m, provided the magnetically
anisotropic behavior while iron, with Msat =1.8 × 106 A/m and
Hc < 2 × 10^3 A/m, provided the soft magnetic behavior.
Experiments on materials with 30% particle concentrations
showed that under uniform magnetic fields class A-A (aligned
BaM) MREs were capable of large deflections in cantilever
beam bending (deflections of 12mm for length 50mm and
magnetic field 1.2 × 105 A/m) whereas all other classes,
including I-A (random BaM) MREs, showed none. Tip
deflection varied linearly with applied field strength. Tip
blocking-force versus deflection experiments were also
conducted on cantilevered A-A specimens. These tests showed
that tip force increased with decreasing free deflection and with
increasing field strength.
INTRODUCTION
Magnetorheological elastomers (MREs) are a novel
class of smart materials, comprised of magnetic particles in a
non-magnetic rubbery matrix, which have gained renewed
interest recently [1,2,3,4,5,6,7,8]. MREs are able to change
Figure 1: Current literature on MRE behavior ascribes shear-stiffening
behavior of MREs to the resistance of long chains of particles to shear
deformation with respect to the applied magnetic field axis, H.
their apparent shear stiffness under the influence of a magnetic
field which has many controls applications including tunable
vibration absorbers and active bushings[9,10]. Existing
literature in the field generally ascribes the shear-stiffening
behavior of MREs to the resistance of long chains of particles,
formed while curing the material within a magnetic field of 1-2
MA/m, to deformation with respect to the magnetic field axis
[11]. (See Figure 1). The perturbation of these chains drives the
particles away from their preferred minimum energy state,
thereby inducing an internal restorative force [12]. While it is
true that the minimum energy state for a chain of particles is
aligned with the external field, an examination of the driving
magnetic phenomena at the particle level revels that soft- and
hard-magnetic materials will behave substantially differently.
The torque T acting on an individual particle is determined by
T = M × H where M is the magnetization of the particle and H
the applied magnetic field. For soft-magnetic materials, such
as iron, M aligns with H yielding T = 0 whereas for hardmagnetic materials M is independent of H such that generally T
≠ 0. The focus of this work is the examination of the resulting
difference in behavior between materials made from hard- and
soft-magnetic filler particles.
Figure 2: Four classes of MRE materials as described by particle alignmentmagnetization pairs. Ellipses show magnetization axes.
2
Copyright © 2009 by ASME
Magnetic filler particles may be classified as either anisotropic
(A, hard-magnetic) or isotropic (I, soft-magnetic), defining two
classifications based on particle magnetization. Additionally,
particle arrangements provide two class distinctions:
anisotropic for particles arranged in chains or isotropic for
particles arranged randomly with no order. Together, this
distinction yields a four classificationa of particles based on
alignment-magnetization pairs, namely I-I, A-I, I-A, and A-A
(Figure 2).
EXPERIMENTAL METHODS
For this work nominally 40-micron iron (Fe) particles
served as the soft-magnetic filler particles (coercive fiels μ0Hc
< 2.5 mT) while nominally 40 micron M-type barium
hexaferrite (BaM) particles served as the hard-magnetic filler
(μ0Hc > 0.4 T). Material classes A-A and A-I were produced by
curing in μ0H ~ 2 T to produce anisotropy in particle
arrangements while material classes I-I and I-A were cured as
mixed in Earth’s field. Dow Corning HS II silicone elastomer
compound was used as the matrix material in a 30% v/v
particle to matrix ratio.
Figure 4: Class A‐A (BaM) sample 5 x 20 x 75 mm under 150 T. Graph paper scale is ¼ in. Class A‐A (shown) deforms while Classes A‐I, I‐A, and I‐I do not (not shown).
RESULTS
During the free cantilever bending test, only samples of class
A-A showed deformation under a magnetic field. Figure 4
shows the deformed shape of the A-A sample at 0H = 0.15 T.
The tip deformation was linear with respect to field strength
(Fig. 5).
Figure 3: Schematic of cantilever bending experiment showing C‐shaped electromagnet, MRE sample with class poling direction (red), and magnetic flux direction (blue). A cantilever actuation test measuring the field dependence of the tip deflection was conducted on samples from all four
classes using a C-shaped electromagnet as shown schematically
in Figure 3. All samples had dimension 5 × 20 × 75 mm3 where
75 mm was the free cantilever length. The displacement was
measured using an optical microscope, and the field strength
was measured with a Lakeshore Gaussmeter. In addition, A
blocking force test was conducted on the class A-A sample by
placing a Shimpo model FGV-0.5x force gauge at specified
distances from its tip. The sample was allowed to free deform
until it contacted the force transducer which measured the
applied force.
Figure 5: Tip deflection versus field strength for class A-A sample in free
cantilever bending experiment of Figure 3.
Material classes A-I, I-I, and I-A showed no deformation for
the range of field strengths tested. The blocking force test of
the sample of class A-A (Fig. 6) showed an increase in force
with increasing field strength and a decrease in force with
increasing tip deflection.
3
Copyright © 2009 by ASME
[3] David York, Xiaojie Wang, and Faramarz Gordaninejad, “A new MR fluid‐elastomer vibration isolator,” J. Intell. Mater. Syst. Struct. 18, 1221 (2007). [4] Hua‐xia Deng and Xing‐long Gong, “Application of magnetorheological elastomer to vibration absorber,” Communications in Nonlinear Science and Numerical Simulation, 13, 1938 (2008). [5] A. Albanese Lerner and K.A Cunefare, “Performance of MRE‐based vibration absorbers,” Intell. Mater. Syst. Struct. 19, 551 (2008). Figure 6: Blocking force vs. field applied strength at tip deflections shown for
cantilever testing of class A-A (BaM) materials
CONCLUSIONS
The results presented show clear differences in
behavior between the class A-A and classes A-I, I-I, and I-A
samples. Class A-A samples produce actuation in cantilever
bending whereas the other classes do not. No tip deflection was
produced even in samples composed of the same magnetic
filler particles, BaM, when particle arrangements were
isotropic, class I-A. The lack of actuation in materials having
the same BaM magnetic filler highlights the dual dependence
on both particle magnetization and particle arrangement. One
interpretation for class I-A (BaM) materials, is that while the
individual particles have internal magnetization, their random
arrangement yields zero net magnetization of the bulk and
hence no internal torque en masse. An alternative view is that
the individual torques generated at the particle level cancel and
therefore generate no bulk response. The lack of actuation in
classes I-I and A-I (Fe) materials supports the assertion that the
soft-magnetic behavior of iron particles, regardless of
alignment, yields no magnetic torque and thereby cannot
generate an internal moment to cause deflection of the sample.
The results of Figure 6 show the ability of the class A-A
samples to do work further highlighting the difference between
class A-A and the other classes.
[6] Saul Opie and Yim Woosoon, “A tunable vibration isolator using a magnetorheological elastomer with a field induced modulus bias,” Proceedings of the ASME International Mechanical Engineering Congress and Exposition, IMECE 2007, 99 (2008). [7] G.Y. Zhou, and Q. Wang, Q. “Use of magnetorheological elastomer in an adaptive sandwich beam with conductive skins. Part I: Magnetoelastic loads in conductive skins,” Inter. J. Solids Struct. 43, 5386 (2006). [8]G.Y. Zhou, and Q. Wang, “Magnetorheological elastomer‐
based smart sandwich beams with nonconductive skins,” Smart Mater. Struct., 14, 1001 2005, p 1001‐1009 [9] G Y Zhou “Shear properties of a magnetorheological elastomer,” Smart Mater. Struct. 12 139 ‐146 (2002) [10] Hua‐Xia Gong Deng, Wang Xing‐Long, and Lian‐Hua, “Development of an adaptive tuned vibration absorber with magnetorheological elastomer,” Smart Mater. Struct. 15, p N111‐16 (2006). [11] L Chen, X L Gong, W H Li, “Microstructures and viscoelastic properties of anisotropic magnetorheological elastomers,” Smart Mater. Struct. 16 p 2645 ‐50 (2007) [12] Y Shen, M F Golnaraghi, G R Heppler, “Experimental Research and Modeling of Magnetorheological Elastomers,” Journal of Intelligent Material Systems and Structures 15 p 27 ‐
35 (2004) ACKNOWLEDGEMENTS
The authors would like to thank several students for their
support: William Hargrave, Rocco Bravaco, Kevin Anderson,
Taylor Kirk, Sean Meehan, Joseph Urcinas.
REFERENCES
[1] T. Lindroos, S. Aalto, E. Jarvinen, T. Karna, M. Meinander,
and T. Kallio, “Dynamic compression testing of a tunable
spring element consisting of a magnetorheological elastomer,”
Smart Mater. Struct. 16, 506 (2004).
[2]G.Y. Zhou, and Q. Wang, “Magnetorheological elastomer‐
based smart sandwich beams with nonconductive skins,” Smart Mater. Struct., 14, 1001 2005, p 1001‐1009 4
Copyright © 2009 by ASME
1
T. Lindroos, S. Aalto, E. Jarvinen, T. Karna, M. Meinander, and T. Kallio, “Dynamic compression testing of a tunable spring element consisting of a magnetorheological elastomer,” Smart Mater. Struct. 16, 506 (2004). 2
G.Y. Zhou, and Q. Wang, “Magnetorheological elastomer‐based smart sandwich beams with nonconductive skins,” Smart Mater. Struct., 14, 1001 2005, p 1001‐1009 3
David York, Xiaojie Wang, and Faramarz Gordaninejad, “A new MR fluid‐elastomer vibration isolator,” J. Intell. Mater. Syst. Struct. 18, 1221 (2007). 4
Hua‐xia Deng and Xing‐long Gong, “Application of magnetorheological elastomer to vibration absorber,” Communications in Nonlinear Science and Numerical Simulation, 13, 1938 (2008). 5
A. Albanese Lerner and K.A Cunefare, “Performance of MRE‐based vibration absorbers,” Intell. Mater. Syst. Struct. 19, 551 (2008). 6
Saul Opie and Yim Woosoon, “A tunable vibration isolator using a magnetorheological elastomer with a field induced modulus bias,” Proceedings of the ASME International Mechanical Engineering Congress and Exposition, IMECE 2007, 99 (2008). 7
G.Y. Zhou, and Q. Wang, Q. “Use of magnetorheological elastomer in an adaptive sandwich beam with conductive skins. Part I: Magnetoelastic loads in conductive skins,” Inter. J. Solids Struct. 43, 5386 (2006). 8
G.Y. Zhou, and Q. Wang, “Magnetorheological elastomer‐based smart sandwich beams with nonconductive skins,” Smart Mater. Struct., 14, 1001 2005, p 1001‐1009 9
G Y Zhou “Shear properties of a magnetorheological elastomer,” Smart Mater. Struct. 12 139 ‐146 (2002) 10
Hua‐Xia Gong Deng, Wang Xing‐Long, and Lian‐Hua, “Development of an adaptive tuned vibration absorber with magnetorheological elastomer,” Smart Mater. Struct. 15, p N111‐16 (2006). 11
L Chen, X L Gong, W H Li, “Microstructures and viscoelastic properties of anisotropic magnetorheological elastomers,” Smart Mater. Struct. 16 p 2645 ‐50 (2007) 12
Y Shen, M F Golnaraghi, G R Heppler, “Experimental Research and Modeling of Magnetorheological Elastomers,” Journal of Intelligent Material Systems and Structures 15 p 27 ‐35 (2004) 5
Copyright © 2009 by ASME