scholarly journals Tuning Elastic Waves in Soft Phononic Crystal Cylinders Via Large Deformation and Electromechanical Coupling

2018 ◽  
Vol 85 (3) ◽  
Author(s):  
Bin Wu ◽  
Weijian Zhou ◽  
Ronghao Bao ◽  
Weiqiu Chen
Keyword(s):  
Large Deformation ◽  
Axial Force ◽  
Electromechanical Coupling ◽  
Phononic Crystal ◽  
Electrical Stimulus ◽  
Critical Voltage ◽  
Electric Voltage ◽  
Propagation Behavior ◽  
Electromechanical Instability ◽  
Longitudinal Stretch

Soft electroactive materials can undergo large deformation subjected to either mechanical or electrical stimulus, and hence, they can be excellent candidates for designing extremely flexible and adaptive structures and devices. This paper proposes a simple one-dimensional soft phononic crystal (PC) cylinder made of dielectric elastomer (DE) to show how large deformation and electric field can be used jointly to tune the longitudinal waves propagating in the PC. A series of soft electrodes, which are mechanically negligible, are placed periodically along the DE cylinder, and hence, the material can be regarded as uniform in the undeformed state. This is also the case for the uniformly prestretched state induced by a static axial force only. The effective periodicity of the structure is then achieved through two loading paths, i.e., by maintaining the longitudinal stretch and applying an electric voltage over any two neighboring electrodes or by holding the axial force and applying the voltage. All physical field variables for both configurations can be determined exactly based on the nonlinear theory of electroelasticity. An infinitesimal wave motion is further superimposed on the predeformed configurations, and the corresponding dispersion equations are derived analytically by invoking the linearized theory for incremental motions. Numerical examples are finally considered to show the tunability of wave propagation behavior in the soft PC cylinder. The outstanding performance regarding the band gap (BG) property of the proposed soft dielectric PC is clearly demonstrated by comparing with the conventional design adopting the hard piezoelectric material. One particular point that should be emphasized is that soft dielectric PCs are susceptible to various kinds of failure (buckling, electromechanical instability (EMI), electric breakdown (EB), etc.), imposing corresponding limits on the external stimuli. This has been carefully examined for the present soft PC cylinder such that the applied electric voltage is always assumed to be less than the critical voltage except for one case, in which we illustrate that the snap-through instability of the axially free PC cylinder made of a generalized Gent material may be used to efficiently trigger a sharp transition in the BGs.

NONEQUILIBRIUM THERMODYNAMICS OF DIELECTRIC ELASTOMERS

2011 ◽  
Vol 03 (02) ◽  
pp. 203-217 ◽  
Author(s):  
XUANHE ZHAO ◽  
SOO JIN ADRIAN KOH ◽  
ZHIGANG SUO
Keyword(s):  
Nonequilibrium Thermodynamics ◽  
Dielectric Elastomer ◽  
Specific Model ◽  
Critical Voltage ◽  
Dielectric Elastomers ◽  
Internal Variables ◽  
Strain Rates ◽  
Dissipative Processes ◽  
Electromechanical Instability ◽  
External Loads

This paper describes an approach to construct models of dielectric elastomers undergoing dissipative processes, such as viscoelastic, dielectric and conductive relaxation. This approach is guided by nonequilibrium thermodynamics, characterizing the state of a dielectric elastomer with kinematic variables through which external loads do work, as well as internal variables that describe the dissipative processes. Within this approach, a method is developed to calculate the critical condition for electromechanical instability. This approach is illustrated with a specific model of a viscoelastic dielectric elastomer, which is fitted to stress-strain curves of a dielectric elastomer (VHB tape), measured at various strain rates. The model shows that a higher critical voltage can be achieved by applying a constant voltage for a shorter time, or by applying ramping voltage with a higher rate. A viscoelastic dielectric elastomer can attain a larger strain of actuation than an elastic dielectric elastomer.

A Two-Way Unidirectional Narrow-Band Acoustic Filter Realized by a Graded Phononic Crystal

2017 ◽  
Vol 84 (9) ◽  
Author(s):  
Yingjie Chen ◽  
Yang Huang ◽  
Chaofeng Lü ◽  
Weiqiu Chen
Keyword(s):  
Band Gap ◽  
Narrow Band ◽  
Phononic Crystal ◽  
Close Relation ◽  
Propagation Characteristic ◽  
Pass Band ◽  
Heterogeneous Structure ◽  
Resonant Frequencies ◽  
Propagation Behavior ◽  
Periodic Components

Unidirectional acoustic transmission is acquired in a one-dimensional graded phononic crystal. The distinct feature of the present design is that waves can propagate unidirectionally at a certain frequency from the left to right, and waves at another frequency can propagate in the opposite direction from the right to left. This two-way asymmetric propagation behavior is realized at the narrow resonant frequencies in the acoustic band gap by a novel mechanism, which is totally linear and obeys the time-reversal symmetry. Simulation shows that for the graded heterogeneous structure, the resonant peaks of frequency in the acoustic band gap for opposite propagation directions become different. In the transmission spectrum, this mechanism corresponds to a pass-band splitting, and each separated peak represents a unidirectional propagation behavior. The separation of two peaks has been proved to have a close relation to the grading degree of the material property in the spatially periodic components. The unique propagation characteristic obtained at resonant frequencies in the band gaps may provide us a new way to realize a two-way unidirectional narrow-band acoustic filter.

Tunable Multimode Filtering of Solid Acoustic Waves in a Three-Component Phononic Crystal Slab

2010 ◽  
Vol 150-151 ◽  
pp. 1625-1639
Author(s):  
Jing Li
Keyword(s):  
Longitudinal Wave ◽  
Acoustic Waves ◽  
Negative Refraction ◽  
Phononic Crystal ◽  
Wave Mode ◽  
Geometrical Parameters ◽  
Transverse Waves ◽  
Propagation Behavior ◽  
The Individual ◽  
Negative Refractions

Using of the multiple scattering methods, we characterize the positive and negative multi-refraction and transmission properties of a solid-based phononic crystal composed of coated solid inclusions in view of its applications in tunable multimode filtering. The geometrical parameters are chosen so that a left-handed longitudinal wave mode and a right-handed transverse wave mode, are simultaneously obtained in this three-component phononic crystal. When multimode Gaussian beams are placed transmitting through the phononic crystal slab, both positive and negative refractions are observed. We then study the individual propagation behavior of different modes. The angle dependent transmission beams with different energy distributions are found at the other side of the slab. Transmitted transverse waves coming from different directions incidence finally walk together into four oriented beams. Meanwhile, longitudinal wave incidence with different directions behaves simply as negative refraction in the slab. A far-field longitudinal wave image can be achieved being excited by a longitudinal wave point source. The three-component phononic crystal slab thus can be served as an alternate in tunable multimode filtering devices.

scholarly journals Piezoelectric time delayed control for nonlinear vibration of nanobeams

2020 ◽  
pp. 146134842092557
Author(s):  
Canchang Liu ◽  
Qingmei Gong ◽  
Yingchao Zhou ◽  
Changcheng Zhou
Keyword(s):  
Time Delay ◽  
Nonlinear Vibration ◽  
Axial Force ◽  
Primary Resonance ◽  
Critical Voltage ◽  
Control Effect ◽  
Critical Position ◽  
Vibration Effect ◽  
Multi Scale ◽  
Governing Differential Equation

The nonlinear vibration effect of nanobeam and problem of the pull-in between the nanobeam and driven plate are the factors which prevent nano-resonator from improving the performance. The nonlinear governing differential equation is built by considering the axial force with piezoelectric controller. The piezoelectric time-delay electrostatic pull-in control is studied and the first-order approximate solution of nonlinear equation is gotten by using the method of multi-scale. The amplitude–frequency and phase frequency response equation of nonlinear vibration system are given for the primary resonance response of the nanobeam. The relationship between the control effect and feedback control parameters is studied. It is found that the piezoelectric time-delay control can change the critical voltage but not the critical position. The axial force can affect the performance of nanobeam.

Selective Band Gap to Suppress the Spurious Acoustic Mode in Film Bulk Acoustic Resonator Structures

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Rafik Serhane ◽  
Fayçal Hadj-Larbi ◽  
Abdelkader Hassein-Bey ◽  
Abdelkrim Khelif
Keyword(s):  
Band Gap ◽  
Electromechanical Coupling ◽  
Lamb Waves ◽  
Phononic Crystal ◽  
Longitudinal Mode ◽  
Acoustic Resonator ◽  
Electromechanical Coupling Coefficient ◽  
Spurious Mode ◽  
Film Bulk Acoustic Resonator ◽  
Film Bulk

In this work, we investigate numerically the propagation of Lamb waves in a film bulk acoustic resonator (FBAR) structure formed by piezoelectric ZnO layer sandwiched between two Mo electrodes coupled with Bragg reflectors; the system is thus considered as a phononic-crystal (PnC) plate. The aim is to suppress the first-order symmetric Lamb wave mode considered as a spurious mode caused by the establishment of a lateral standing wave due to the reflection at the embedded lateral extremities of the structure; this spurious mode is superposing to the main longitudinal mode resonance of the FBAR. The finite element study, using harmonic and eigen-frequency analyses, is performed on the section of FBAR structure coupled with the PnC. In the presence of PnC, the simulation results show the evidence of a selective band gap where the parasitic mode is prohibited. The quality factor of the FBAR is enhanced by the introduction of the PnC. Indeed, the resonance and antiresonance frequencies passed from 1000 and 980 (without PnC) to 2350 and 1230 (with PnC), respectively. This is accompanied by a decrease in the electromechanical coupling coefficient from 10.60% to 6.61%.

Large deformation and electromechanical instability of a dielectric elastomer tube actuator

2010 ◽  
Vol 108 (7) ◽  
pp. 074113 ◽  
Author(s):  
Jian Zhu ◽  
Hristiyan Stoyanov ◽  
Guggi Kofod ◽  
Zhigang Suo
Keyword(s):  
Large Deformation ◽  
Dielectric Elastomer ◽  
Electromechanical Instability ◽  
Dielectric Elastomer Tube
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