Use of the complex dynamic shear stiffness of a visco‐elastic liquid to illustrate the origins of structural damping

1976 ◽  
Vol 60 (S1) ◽  
pp. S74-S74
Author(s):  
R. A. Ely
Keyword(s):  
Shear Stiffness ◽  
Dynamic Shear ◽  
Structural Damping ◽  
Complex Dynamic ◽  
Elastic Liquid

Dynamic shear stiffness and damping ratio of marine calcareous and siliceous sands

2018 ◽  
Vol 38 (4) ◽  
pp. 315-322 ◽  
Author(s):  
Hamed Javdanian ◽  
Yaser Jafarian
Keyword(s):  
Damping Ratio ◽  
Shear Stiffness ◽  
Dynamic Shear ◽  
Stiffness And Damping

scholarly journals Experimental Investigation of Dynamic Characteristics of Subsea Sand-Silt Mixtures

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Tugen Feng ◽  
Yu Tang ◽  
Qiyenan Wang ◽  
Jian Zhang ◽  
Jian Song
Keyword(s):  
Cement Content ◽  
Damping Ratio ◽  
Shear Stiffness ◽  
Confining Pressure ◽  
Dynamic Responses ◽  
Resonant Column ◽  
Dynamic Shear ◽  
Column Tests ◽  
Mixture Ratio ◽  
Curing Age

In this paper, extensive resonant column tests were conducted to investigate dynamic responses of subsea sand-silt mixtures. The effects of confining pressure, mixture ratio, curing age, and cement content were evaluated. For the test condition considered in this study, the measured damping ratio is the smallest when the ratio of subsea sand to silt is in a range of 1.5 to 2.0. Moreover, unsolidified subsea sand-silt mixed at a ratio of 1.5 has almost the same maximum shear stiffness as the pure sand. For solidified subsea sand-silt mixture, cement can significantly increase the dynamic shear stiffness when the curing age is less than 14 days. However, the increase of the maximum dynamic shear stiffness is negligible when the curing age is longer than 14 days. When the cement content is 2%, the damping ratio of the solidified mixtures is very close to that of the unsolidified mixture. When the cement content is higher than 4%, the damping ratio of the solidified mixtures reduces significantly. This is mainly due to hydration reactions occurring in the solidified mixtures.

Comparative Study on the Hysteresis Performance of the Metal Rubber Vibration Isolating Bearing with Different Height-Width Ratio Parameter

2014 ◽  
Vol 1079-1080 ◽  
pp. 191-194
Author(s):  
Yan Guo Zhou ◽  
Jian Jiang
Keyword(s):  
Seismic Isolation ◽  
Shear Stiffness ◽  
Width Ratio ◽  
Damping Capacity ◽  
Dynamic Shear ◽  
Rubber Material ◽  
Model Method ◽  
Metal Rubber ◽  
Hysteresis Properties ◽  
Selection Of

A new kind of Metal Rubber material vibration isolating bearing is developed and the MR bearings with three different height-width ratio are manufactured. The dynamic shear hysteresis properties of the MR bearings are tested. The theoretical dynamic model method is adopted for the comparative analysis. The experimental results shows that with the H-W ratio decrease, the effective shear stiffness and the effective damping capacity of MR vibration isolating bearing will increase, and the total energy dissipation increases greatly. The selection of the H-W ratio of the MR vibration isolating bearing become an important issue in the structural seismic isolation design.

scholarly journals THE SHEAR STRENGTH AND DYNAMIC SHEAR STIFFNESS OF SOME NEW ZEALAND VOLCANIC ASH SOILS

2005 ◽  
Vol 45 (3) ◽  
pp. 9-20 ◽  
Author(s):  
VAUGHAN MEYER ◽  
TAM LARKIN ◽  
MICHAEL PENDER
Keyword(s):  
Shear Strength ◽  
New Zealand ◽  
Volcanic Ash ◽  
Shear Stiffness ◽  
Dynamic Shear ◽  
Volcanic Ash Soils

MAGNETOSTRICTIVE PHENOMENA IN MAGNETORHEOLOGICAL ELASTOMERS

2002 ◽  
Vol 16 (17n18) ◽  
pp. 2412-2418 ◽  
Author(s):  
J. M. GINDER ◽  
S. M. CLARK ◽  
W. F. SCHLOTTER ◽  
M. E. NICHOLS
Keyword(s):  
Dynamic Shear ◽  
Iron Particles ◽  
Resonant Structure ◽  
Complex Dynamic ◽  
Low Frequencies ◽  
Magnetorheological Elastomers ◽  
Shear Moduli ◽  
High Frequencies ◽  
Large Elongation ◽  
Magnetostrictive Composites

A host of fascinating and useful magnetic phenomena are found in composites containing magnetizable particles in viscoelastic solids. Embedding magnetically soft iron particles in natural rubber produces a class of magnetostrictive composites sometimes termed magnetorheological (MR) elastomers. We have previously shown that these materials can exhibit viscoelastic moduli that increase substantially in an applied magnetic field. In this paper, we incorporate MR elastomers in a simple resonant structure called a tuned absorber to measure the complex dynamic shear moduli of these materials at high frequencies. We find that the fluid-induced modulus increase in MR elastomers is substantial even at kilohertz mechanical frequencies. As in previous measurements at low frequencies, the moduli are generally found to decrease with strain amplitude. We also report preliminary measurements of the relatively large elongation of these materials in applied magnetic fields.

Role of Magnetization Anisotropy in the Active Behavior of Magnetorheological Elastomers

2011 ◽  
Author(s):  
Paris R. von Lockette ◽  
Samuel E. Lofland
Keyword(s):  
Magnetic Field ◽  
Magnetic Particles ◽  
Shear Stiffness ◽  
Shape Anisotropy ◽  
Spherical Particles ◽  
Dynamic Shear ◽  
Soft Magnetic ◽  
Magnetorheological Elastomers ◽  
Particle Level

Magnetorheological elastomers (MREs) are a re-emerging class of smart materials whose novel behavior stems from their response to magnetic fields. Historically comprised of soft-magnetic carbonyl (spherical) iron particles embedded in highly compliant matrix materials, MRE research has focused on their apparent change in shear modulus (in excess of 60%) under a magnetic field. Recent work by the authors has departed from the experimental and theoretical focus on MREs made from soft-magnetic particles (S-MREs) to investigate MREs having hard-magnetic particle inclusions (H-MREs). While H-MRE materials do not perform well in dynamic shear stiffness applications when compared to the traditional S-MREs, H-MREs provide remotely powered, fully reversible actuation capabilities that S-MREs are unable to achieve. In addition, in the same dynamic shear stiffness applications these H-MREs provide a measure of active control of which S-MREs are also incapable. This work examines the role that particle magnetization, developed due to shape anisotropy, plays in the actuation response S-MREs in contrast to H-MREs. H-MRE response is predicated on the response of the hard-magnetic particles to the external magnetic field and to neighboring particles. Since hard-magnetic particles have an internal preferred magnetic orientation, they are able to generate torques at the particle level, T = M × B, where T is the torque density, M is the magnetization, and B is the local magnetic flux density. In contrast, soft-magnetic particles may develop an induced magnetization when exposed to an external field if the particles exhibit shape anisotropy. This induced magnetization is also capable of producing torque at the particle level, however, spherical particles like those historically used in MREs are geometrically isotropic and therefore do not develop induced magnetization either and consequently the widely studied MREs comprised of soft-magnetic spherical particles generate no torque at the particle level. Shape anisotropy further complicates the mechanical response by inducing Eshelby-type shape-dependent effects on the mechanical stresses developed local to the particle. These effects vary the local particle rotation, resulting from a given macroscopic loading, and in turn affect the local magnetic field by changing the particle’s magnetization axis with respect to the external field. The result is a material system whose elastomagnetic response depends on particle shape and orientation as well as on particle magnetization. In previous works the authors used barium hexaferrite (a hard magnetic material) and carbonyl iron powders to generate MRE materials having varying particle alignment and magnetization permutations. These materials were examined in cantilever bending modes to assess and differentiate their abilities as bending actuators. In this work, finite element studies mirroring the bending tests are performed to determine the role of particle/magnetization anisotropy on the behavior. Results show strong dependence on particle shape anisotropy.

Actuation Behavior in Patterned Magnetorheological Elastomers: Simulation, Experiment, and Modeling

2012 ◽  
Author(s):  
Paris von Lockette
Keyword(s):  
Magnetic Field ◽  
Smart Materials ◽  
Magnetic Particles ◽  
Constitutive Models ◽  
Barium Hexaferrite ◽  
Shear Stiffness ◽  
Silicone Elastomer ◽  
Dynamic Shear ◽  
Magnetorheological Elastomers ◽  
Magnetic Symmetry

Magnetorheological elastomers (MREs) are an emerging class of smart materials whose mechanical behavior varies in the presence of a magnetic field. Historically MREs have been comprised of soft-magnetic iron particles in a compliant matrix such as silicone elastomer. Numerous works have experimentally cataloged the MRE effect, or increase in shear stiffness, versus the applied field. Several other researchers have derived constitutive models for the large deformation behavior of MREs. In almost all cases the arrays of embedded particles, and or the particles themselves, are assumed magnetically symmetric with respect to the external magnetic field, i.e. the bulk materials exhibit magnetic symmetry in the given experimental or analytical configuration. In this work the author presents results of dynamic shear experiments, Lagrangian dynamic analysis, and static shear simulations on MRE material systems that exhibit broken magnetic symmetry. These new materials utilize barium hexaferrite powder as the magnetically anisotropic filler combined with a compliant silicone elastomer matrix. Simulations of representative laminate structures comprised of varied arrays of magnetic particles exhibit novel actuation behaviors including reversible shearing deformation, variable magnetostriction, and most surprisingly, piezomagnetism. Results of dynamic shear experiments and analytical modeling support predicted shearing actuation responses in MREs having broken symmetry and only in those systems.

Rheological Properties of “Dry Water”

2011 ◽  
Author(s):  
Onur Taylan ◽  
Halil Berberoglu
Keyword(s):  
Rheological Properties ◽  
Shear Viscosity ◽  
Volume Ratio ◽  
Rotational Frequency ◽  
Dynamic Shear ◽  
Complex Dynamic ◽  
Fumed Silica Nanoparticles ◽  
Fuel Storage ◽  
Novel Material ◽  
Dry Water

This study reports the rheological properties of the novel material “dry water” which contains about 98% by weight water but resembles a dry powder. Dry water is a water-in-air inverse foam which consists of microscopic water droplets encapsulated with hydrophobic fumed-silica nanoparticles. This novel material offers a large surface to volume ratio on the order of 2 × 105 m2/m3 for the gas and water phases. Thus, it provides a convenient medium for surface area limited processes and finds applications from cosmetics to gaseous fuel storage. In this study both steady and dynamic rheological properties of dry water were measured. In particular, the elastic (G′) and viscous (G″) moduli, and the complex dynamic shear viscosity (η*) were recovered from experimental data. Results showed that both the elastic and viscous moduli decreased with increasing strain at strains larger than 4%, and both moduli are weak functions of rotational frequency. Complex dynamic shear viscosity decreased with strain and rotational frequency. When compared with the studies in literature, rheological experiments and obtained results indicated that dry water behaves as a gel rheologically under the investigated conditions.

Sign in / Sign up

Export Citation Format

Share Document