scholarly journals Ultrahigh energy-dissipation elastomers by precisely tailoring the relaxation of confined polymer fluids

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jin Huang ◽  
Yichao Xu ◽  
Shuanhu Qi ◽  
Jiajia Zhou ◽  
Wei Shi ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Mechanical Energy ◽  
Operating Frequency ◽  
Ultrahigh Energy ◽  
Frequency Range ◽  
Polymer Fluids ◽  
Elastic Networks ◽  
Broad Frequency Range ◽  
Polymer Fluid ◽  
Confined Polymer

AbstractEnergy-dissipation elastomers relying on their viscoelastic behavior of chain segments in the glass transition region can effectively suppress vibrations and noises in various fields, yet the operating frequency of those elastomers is difficult to control precisely and its range is narrow. Here, we report a synergistic strategy for constructing polymer-fluid-gels that provide controllable ultrahigh energy dissipation over a broad frequency range, which is difficult by traditional means. This is realized by precisely tailoring the relaxation of confined polymer fluids in the elastic networks. The symbiosis of this combination involves: elastic networks forming an elastic matrix that displays reversible deformation and polymer fluids reptating back and forth to dissipate mechanical energy. Using prototypical poly (n-butyl acrylate) elastomers, we demonstrate that the polymer-fluid-gels exhibit a controllable ultrahigh energy-dissipation property (loss factor larger than 0.5) with a broad frequency range (10−2 ~ 108 Hz). Energy absorption of the polymer-fluid-gels is over 200 times higher than that of commercial damping materials under the same dynamic stress. Moreover, their modulus is quasi-stable in the operating frequency range.

Energy dissipation rate in a baffled vessel with pitched blade turbine impeller

1991 ◽  
Vol 56 (9) ◽  
pp. 1856-1867 ◽  
Author(s):  
Zdzisław Jaworski ◽  
Ivan Fořt
Keyword(s):  
Energy Dissipation ◽  
Cross Sections ◽  
Mechanical Energy ◽  
Vessel Diameter ◽  
Energy Dissipation Rate ◽  
Mean Velocity ◽  
Agitated Vessel ◽  
Radial Profiles ◽  
Pitched Blade Turbine ◽  
Turbine Impeller

Mechanical energy dissipation was investigated in a cylindrical, flat bottomed vessel with four radial baffles and the pitched blade turbine impeller of varied size. This study was based upon the experimental data on the hydrodynamics of the turbulent flow of water in an agitated vessel. They were gained by means of the three-holes Pitot tube technique for three impeller-to-vessel diameter ratio d/D = 1/3, 1/4 and 1/5. The experimental results obtained for two levels below and two levels above the impeller were used in the present study. Radial profiles of the mean velocity components, static and total pressures were presented for one of the levels. Local contribution to the axial transport of the agitated charge and energy was presented. Using the assumption of the axial symmetry of the flow field the volumetric flow rates were determined for the four horizontal cross-sections. Regions of positive and negative values of the total pressure of the liquid were indicated. Energy dissipation rates in various regions of the agitated vessel were estimated in the range from 0.2 to 6.0 of the average value for the whole vessel. Hydraulic impeller efficiency amounting to about 68% was obtained. The mechanical energy transferred by the impellers is dissipated in the following ways: 54% in the space below the impeller, 32% in the impeller region, 14% in the remaining part of the agitated liquid.

scholarly journals Spatial Decomposition of a Broadband Pulse Caused by Strong Frequency Dispersion of Sound in Acoustic Metamaterial Superlattice

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 125
Author(s):  
Yuqi Jin ◽  
Yurii Zubov ◽  
Teng Yang ◽  
Tae-Youl Choi ◽  
Arkadii Krokhin ◽  
...  
Keyword(s):  
Acoustic Pulse ◽  
Frequency Dispersion ◽  
Transmission Band ◽  
Lateral Position ◽  
Operating Frequency ◽  
Frequency Range ◽  
Frequency Spectra ◽  
Acoustic Metamaterial ◽  
Superlattice Structure ◽  
Broadband Pulse

An acoustic metamaterial superlattice is used for the spatial and spectral deconvolution of a broadband acoustic pulse into narrowband signals with different central frequencies. The operating frequency range is located on the second transmission band of the superlattice. The decomposition of the broadband pulse was achieved by the frequency-dependent refraction angle in the superlattice. The refracted angle within the acoustic superlattice was larger at higher operating frequency and verified by numerical calculated and experimental mapped sound fields between the layers. The spatial dispersion and the spectral decomposition of a broadband pulse were studied using lateral position-dependent frequency spectra experimentally with and without the superlattice structure along the direction of the propagating acoustic wave. In the absence of the superlattice, the acoustic propagation was influenced by the usual divergence of the beam, and the frequency spectrum was unaffected. The decomposition of the broadband wave in the superlattice’s presence was measured by two-dimensional spatial mapping of the acoustic spectra along the superlattice’s in-plane direction to characterize the propagation of the beam through the crystal. About 80% of the frequency range of the second transmission band showed exceptional performance on decomposition.

Design of a Variable Thickness Plate to Focus Bending Waves

2012 ◽  
Author(s):  
Noah H. Schiller ◽  
Sz-Chin Steven Lin ◽  
Randolph H. Cabell ◽  
Tony Jun Huang
Keyword(s):  
Numerical Simulations ◽  
Thin Plate ◽  
Traveling Waves ◽  
Variable Thickness ◽  
Focal Point ◽  
Frequency Range ◽  
Additional Energy ◽  
Broad Frequency Range ◽  
Bending Waves ◽  
Energy Dissipated

This paper describes the design of a thin plate whose thickness is tailored in order to focus bending waves to a desired location on the plate. Focusing is achieved by smoothly varying the thickness of the plate to create a type of lens, which focuses structure-borne energy. Damping treatment can then be positioned at the focal point to efficiently dissipate energy with a minimum amount of treatment. Numerical simulations of both bounded and unbounded plates show that the design is effective over a broad frequency range, focusing traveling waves to the same region of the plate regardless of frequency. This paper also quantifies the additional energy dissipated by local damping treatment installed on a variable thickness plate relative to a uniform plate.

Mechanical Energy Dissipation and Performance in Alpine Ski Racing

2008 ◽  
Vol 40 (Supplement) ◽  
pp. S165 ◽  
Author(s):  
Robert Reid ◽  
Matthias Gilgien ◽  
Tron Moger ◽  
Håvard Tjørhom ◽  
Per Haugen ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Mechanical Energy ◽  
Mechanical Energy Dissipation ◽  
And Performance

Virtual Coupling Control Method for Robotic Gait

2013 ◽  
Vol 278-280 ◽  
pp. 629-632
Author(s):  
Li Peng Yuan ◽  
Amur Al Yahmedi ◽  
Li Ming Yuan
Keyword(s):  
Energy Dissipation ◽  
Hybrid Model ◽  
Control Strategy ◽  
Control Method ◽  
Mechanical Energy ◽  
Control Laws ◽  
Gait Patterns ◽  
Walking Gait ◽  
Virtual Coupling ◽  
Mechanical Energy Dissipation

Here, we consider the walking gait patterns. And we presented a hybrid model for a passive 2D walker with knees and point feet. The dynamics of this model were fully derived analytically. We have also proposed virtual coupling control laws. The control strategy is formed by taking into account the features of mechanical energy dissipation and restoration. And we also prove some walking rules maybe true.

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