scholarly journals Band-Gap Properties of Finite Locally Resonant Beam Suspended Periodically with Two-Degree-of-Freedom Force Type Resonators

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 716
Author(s):  
Hangyuan Lv ◽  
Shangjie Li ◽  
Xianzhen Huang ◽  
Zhongliang Yu
Keyword(s):  
Band Gap ◽  
Low Frequency ◽  
Degree Of Freedom ◽  
Analysis Approach ◽  
The Finite Element Method ◽  
Motion Equations ◽  
Resonant Beam ◽  
Propagation Properties ◽  
Two Degree Of Freedom ◽  
Transmission And Reflection

The propagation properties of waves in finite Timoshenko locally resonant (LR) beams resting on forced vibrations and periodically attached two-degree-of-freedom force-type resonators are studied by the wave-based analysis approach. By calculating the motion equations of the beam, the transmission and reflection matrices of waves at the resonator attached point are first derived, and the forced vibration response of the finite periodic beam is deduced by the wave-based approach. Several examples are also analyzed by the finite element method to verify the high accuracy of the developed wave-based analysis approach. Numerical results show that wider low-frequency band-gaps exist in this type of LR beams. It was also found that the resonator masses and spring stiffnesses caused different effects on the band-gap properties of the combined LR beam. The desired band-gap widths of the LR beam can be tuned by adjusting the mass blocks and spring stiffness in the resonators based on the results.

scholarly journals A Wave-Based Vibration Analysis of a Finite Timoshenko Locally Resonant Beam Suspended with Periodic Uncoupled Force-Moment Type Resonators

Crystals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1132
Author(s):  
Hangyuan Lv ◽  
Yimin Zhang
Keyword(s):  
Vibration Analysis ◽  
Low Frequency ◽  
Bending Moment ◽  
Analysis Approach ◽  
Structural Elements ◽  
Frequency Range ◽  
Resonant Beam ◽  
Force Moment ◽  
A Cell ◽  
Two Degree Of Freedom

This paper first employs and develops an exact wave-based vibration analysis approach to investigate a finite Timoshenko beam carrying periodic two-degree-of-freedom (2-DOF) uncoupled force-moment type resonators. In the approach, vibrations are described as structural waves that propagate along uniform structural elements and reflected and transmitted at structural discontinuities. Each uncoupled force-moment type resonator is considered as a cell which injects waves into the distributed beam through the transverse force and the bending moment at the attached point. By assembling wave relations of the cells into the beam, the forced vibration problem of the locally resonant (LR) structure is turned to be the solution to a related set of matrix equations. In addition, the parametric analysis provides an efficient method to obtain wide low-frequency range band-gaps. Accuracy of the proposed wave-based vibration analysis approach is demonstrated by the simulated and measured results of two sets of beam-like resonator samples.

scholarly journals A Two-Degree-of-Freedom Cantilever-Based Vibration Triboelectric Nanogenerator for Low-Frequency and Broadband Operation

Electronics ◽  
2019 ◽  
Vol 8 (12) ◽  
pp. 1526 ◽  
Author(s):  
Gang Tang ◽  
Fang Cheng ◽  
Xin Hu ◽  
Bo Huang ◽  
Bin Xu ◽  
...  
Keyword(s):  
Output Voltage ◽  
Low Frequency ◽  
Degree Of Freedom ◽  
Triboelectric Nanogenerator ◽  
Energy Harvesters ◽  
Harvesting Technique ◽  
Wide Range ◽  
Operating Bandwidth ◽  
Self Powered ◽  
Two Degree Of Freedom

With the continual increasing application requirements of broadband vibration energy harvesters (VEHs), many attempts have been made to broaden the bandwidth. As compared to adopted only a single approach, integration of multi-approaches can further widen the operating bandwidth. Here, a novel two-degree-of-freedom cantilever-based vibration triboelectric nanogenerator is proposed to obtain high operating bandwidth by integrating multimodal harvesting technique and inherent nonlinearity broadening behavior due to vibration contact between triboelectric surfaces. A wide operating bandwidth of 32.9 Hz is observed even at a low acceleration of 0.6 g. Meanwhile, the peak output voltage is 18.8 V at the primary resonant frequency of 23 Hz and 1 g, while the output voltage is 14.9 V at the secondary frequency of 75 Hz and 2.5 g. Under the frequencies of these two modes at 1 g, maximum peak power of 43.08 μW and 12.5 μW are achieved, respectively. Additionally, the fabricated device shows good stability, reaching and maintaining its voltage at 8 V when tested on a vacuum compression pump. The experimental results demonstrate the device has the ability to harvest energy from a wide range of low-frequency (<100 Hz) vibrations and has broad application prospects in self-powered electronic devices and systems.

A two-degree-of-freedom string-driven rotor for efficient energy harvesting from ultra-low frequency excitations

Energy ◽  
2020 ◽  
Vol 196 ◽  
pp. 117107
Author(s):  
Qinxue Tan ◽  
Kangqi Fan ◽  
Kai Tao ◽  
Liya Zhao ◽  
Meiling Cai
Keyword(s):  
Energy Harvesting ◽  
Low Frequency ◽  
Degree Of Freedom ◽  
Efficient Energy ◽  
Two Degree Of Freedom

Two degree of freedom vibration based electromagnetic energy harvester for bridge health monitoring system

2020 ◽  
pp. 1045389X2095945
Author(s):  
Muhammad Masood Ahmad ◽  
Farid Ullah Khan
Keyword(s):  
Cantilever Beam ◽  
Energy Harvester ◽  
Low Frequency ◽  
Open Circuit ◽  
Electromagnetic Energy ◽  
Degree Of Freedom ◽  
Mode Shapes ◽  
Fixed End ◽  
Two Degree Of Freedom ◽  
Maximum Voltage

This paper presents an electromagnetic energy harvester to extract low frequency and low acceleration vibration energy available in a bridge environment. The developed harvester is a multi-mode oscillator with dual electromagnetic transduction mechanisms. The harvester consists of two cantilever beams. The first cantilever beam is split into two equal pieces along its length and the second beam placed in between them coming back to the fixed end and attached at outer end to the first beam. This way instead of a long conventional cantilever beam a compact harvester is fabricated. Two magnets as proof masses are attached to each free end of the beam making it a two degree of freedom system (2-DOF). The magnets are positioned to oscillate inside hand wound coils during operation. An analytical model was developed and COMSOL multiphysics was used to simulate the mode shapes of the harvester. The mathematical model was simulated for open circuit voltage in MATLAB and showed closely matching results with the experimental values. The harvester is characterized in lab for its performance under sinusoidal vibrations at low frequency (3 Hz–15 Hz) and low acceleration (0.01–0.09 g) levels. The 2-DOF harvester has two resonant frequencies of 4.4 Hz and 5.5 Hz and a volume of 333 cm3. It produces maximum voltage of 0.6 V at first resonance on coil-1 and maximum voltage of 1.2 V on coil-2 at second resonance at 0.09 g. At acceleration of 0.09 g the harvester produced 2.51 mW at first resonant frequency and 10.7 mW at second resonance. Moreover, the AC output voltage of the harvester is rectified to DC voltage by a three-stage Cockcroft-Walton multiplier type circuit. The DC power output at 0.05 g was 0.939 mW at first resonance and 0.956 mW at second resonance while maximum voltages of 5.4 V on coil-1 and 4 V on coil-2 were produced.

Research on low-frequency band gap property of a hybrid phononic crystal

2018 ◽  
Vol 32 (15) ◽  
pp. 1850165 ◽  
Author(s):  
Yake Dong ◽  
Hong Yao ◽  
Jun Du ◽  
Jingbo Zhao ◽  
Ding Chao ◽  
...  
Keyword(s):  
Band Gap ◽  
Transmission Loss ◽  
Displacement Vector ◽  
Phononic Crystal ◽  
Influence Factors ◽  
Low Frequency ◽  
Bragg Scattering ◽  
The Finite Element Method ◽  
Flat Bands ◽  
Resonance Band

A hybrid phononic crystal has been investigated. The characteristic frequency of XY mode, transmission loss and displacement vector have been calculated by the finite element method. There are Bragg scattering band gap and local resonance band gap in the band structures. We studied the influence factors of band gap. There are many flat bands in the eigenfrequencies curve. There are many flat bands in the curve. The band gap covers a large range in low frequency. The band gaps cover more than 95% below 3000 Hz.

scholarly journals Analysis and Optimization of Micro Speaker-Box Using a Passive Radiator in Portable Device

2017 ◽  
Vol 42 (4) ◽  
pp. 753-760 ◽  
Author(s):  
Yuan-Wu Jiang ◽  
Joong-Hak Kwon ◽  
Hyung-Kyu Kim ◽  
Sang-Moon Hwang
Keyword(s):  
Rapid Development ◽  
Low Frequency ◽  
Main Concern ◽  
The Finite Element Method ◽  
Acoustic Characteristics ◽  
Acoustic Performance ◽  
Tablet Pcs ◽  
Electromagnetic Vibration ◽  
The One ◽  
Two Degree Of Freedom

Abstract With the rapid development of multimedia devices such as smart phones and tablet PCs, microspeakers have been recently increasingly used for audio equipment. Improving the acoustic performance of a microspeaker is always a main concern, especially in the low frequency range. To avoid sound cancelation, a microspeaker unit is usually inserted into a speaker box. A passive radiator is also used in speaker boxes to improve the sound performance in the loudspeaker system. However, passive radiators have not been applied into microspeaker system. In this study, a speaker box with a passive radiator was analyzed and optimized to achieve a higher Sound Pressure Level (SPL) in a microspeaker system. The Finite Element Method (FEM), two-degree-of-freedom (DOF) vibration theory, and a plane circular piston sound source were used to study the electromagnetic, vibration, and acoustic characteristics, respectively. Optimization was conducted by changing the mass, stiffness, and size of the passive radiator. Based on the optimized parameters, a new sample was manufactured. The experiment results show that the SPL of the optimized speaker box with a passive radiator is improved by 5 dB at 200 Hz compared with the one without a radiator. The analysis results also matched the experiment results.

scholarly journals Study on Low-Frequency Band Gap Characteristics of a New Helmholtz Type Phononic Crystal

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1379
Author(s):  
Dong-Hai Han ◽  
Jing-Bo Zhao ◽  
Guang-Jun Zhang ◽  
Hong Yao
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Band Gap ◽  
Lattice Constant ◽  
Phononic Crystal ◽  
Low Frequency ◽  
Equivalent Model ◽  
Frequency Noise ◽  
The Finite Element Method ◽  
Symmetric Structure

In order to solve the problem of low-frequency noise of aircraft cabins, this paper presents a new Helmholtz type phononic crystal with a two-dimensional symmetric structure. Under the condition of the lattice constant of 62 mm, the lower limit of the first band gap is about 12 Hz, and the width is more than 10 Hz, thus the symmetric structure has distinct sound insulation ability in the low-frequency range. Firstly, the cause of the low-frequency band gap is analyzed by using the sound pressure field, and the range of band gaps is calculated by using the finite element method and the spring-oscillator model. Although the research shows that the finite element calculation results are basically consistent with the theoretical calculation, there are still some errors, and the reasons for the errors are analyzed. Secondly, the finite element method and equivalent model method are used to explore the influence of parameters of the symmetric structure on the first band gap. The result shows that the upper limit of the first band gap decreases with the increase of the lattice constant and the wedge height and increases with the increase of the length of wedge base; the lower limit of the band gap decreases with the increase of the wedge height and length of wedge base and is independent of the change of lattice constant, which further reveals the essence of the band gap formation and verifies the accuracy of the equivalent model. This study provides some theoretical support for low-frequency noise control and broadens the design idea of symmetric phononic crystal.

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