Polarization bandgaps and fluid-like elasticity in fully solid elastic metamaterials

by:Ultimate     2020-11-24
In sound waves and sound waves, elastic waves exhibit rich polarization properties.
By design based on three-
The size of the local resonance unit of the opposite sex, here we have proved the polarization bandwidth and such as \"fluid-
Elastic, for example.
We construct elastic rods with unusual vibration properties, which we represent as \"meta-rods’.
By measuring the vibration response under bending, longitudinal and torsional excitation, we find that each vibration mode can be selectively suppressed.
In particular, we have observed in a limited frequency range that all bending vibrations are prohibited, whereas longitudinal vibrations are allowed --
The unique nature of the fluid.
In another case, the torsional vibration can be significantly suppressed.
Through the analysis of band structure and the effective medium with infinite mass density and negative moment of inertia, the experimental results are well explained.
Our work opens up a way for effective separation and control of elastic waves with different polarization in all solid structures.
These super materials make one unit at a time.
Unit cells are super connected together by Acrylicglue.
Materials: Wacker silicone rubber RTV-
2 Elastosil M4440, decorated with epoxy resin with transparent cast flowers.
To measure the response spectrum under lateral and longitudinal excitation, we used a waveform generator (Agilent 33220A)
A pulse coverage of 0. 5–3.
5 khz to induction cooker (
Br ü el and Kj æ r excitation class4809)
Through the power amplifier.
The sample is super
Stick to the aluminum plate
For lateral excitation, the sample and aluminum plate are supported by two parallel low levels
Limit the motion to a friction slide track in a single direction.
Then one side of the aluminum plate is securely attached to the rocking bed.
For longitudinal excitation, a thicker aluminum plate is used so that the bending mode of the plate is located above the frequency range we are interested in.
The center of the board is connected directly to the rocking bed. Two tri-
Axial accelerometer (Dytran 3023A)were adhesive-
Security deposit for related positions.
Details of the experimental device-
Ups can be seen more easily.
The accelerometer measures vibration in the direction of excitation.
The exterior of our sample is relatively hard and the deformation is minimal.
Nevertheless, to obtain the best results, we measured 24 points on the top surface of the sample and calculated the response function using the arithmetic mean.
Record signals with a digital oscilloscope (
Agilent DSO6014A).
In order to measure the reverse response, Yuan
The rod is fixed on the rotating table at the center of the bottom axial direction.
The top is fixed on the DC motor connected to the waveform generator.
The two accelerometer measure the tangent acceleration at the top and bottom of the sample.
Vibration profile ()
Get as follows.
A piece of aluminum foil in the kitchen (thickness 0. 02u2009mm)
Adhere to the surface of the sample to be measured, which increases the reflectivity.
Laser Doppler vibration meter (Graphtec AT500-05)
Was installed in a two
Scan the surface point by point in the three-dimensional mobile translation phase.
Our translation phase covers only four cell units with limited travel.
The laser beam is perpendicular to the measured surface, parallel to the excitation force.
The sample is excited by a Shaker driven by a sine signal, and the measurement data is recorded by the lockin amplifier (
Stanford research SR830).
Numerical Simulation using three-
Dimensions solid mechanics module in COMSOL multi-physics (v4. 3a).
The frequency band structure and characteristic mode are solved by using the characteristic frequency research, while the frequency response function passes through the frequency-domain study.
The parameters used in the simulation are: Young\'s modulus = 3 for epoxy resin.
8gpa gpa, Poisson\'s ratio = 0.
350, mass density = 1,130 kgm;
For cylinders, = gpa, = 0.
250, = 7,850 kgm;
For silicone rubber, = 3. 3u2009MPa, =0.
477, = 1,245 kg/m.
In the calculation of the frequency response function, a loss is added to the Young\'s modulus of silicone rubber, that is, = 3. 3+0. 3u2009MPa.
For clear observation, the displacement profile shown was obtained without dissipation.
The data in this study can be obtained on request from the corresponding authors.
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