Low frequency property of a fractal vibration model for a concrete beam

Fractals ◽  
2021 ◽  
Author(s):  
Chun-Hui He ◽  
Chao Liu ◽  
Ji-Huan He ◽  
Khaled A. Gepreel
Keyword(s):  
Concrete Beam ◽  
Low Frequency ◽  
Frequency Property ◽  
Vibration Model

scholarly journals Development of a finite element human vibration model for use in spacecraft coupled loads analysis

2018 ◽  
Vol 38 (2) ◽  
pp. 839-851 ◽  
Author(s):  
Nancy J Currie-Gregg ◽  
Kelly Carney
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Joint Stiffness ◽  
Low Frequency ◽  
Nonlinear Dynamic Response ◽  
Vibration Model ◽  
Loads Analysis ◽  
Impact Attenuation ◽  
Coupled Loads Analysis ◽  
Coupled Loads

Finite element human vibration models were developed and implemented for use in human-tended spacecraft-coupled loads analysis, an analytical process used to predict low-frequency spacecraft loads which occur during dynamic phases of flight of such as launch, ascent, or ascent aborts. Human vibration may also affect stress predictions for spacecraft systems which the crew interacts with, such as crew seats and crew impact attenuation systems. These human vibration models are three-dimensional, distributed-mass representations of 1st-percentile female, 50th-percentile male, and 99th-percentile male American crew members and provide a relatively simple linear and low-load representation of the nonlinear dynamic response of a seated human. The most significant features of these finite element models are anthropometrically based geometric human mass distribution, soft tissue vibration attributes, and skeleton and joint stiffness.

scholarly journals Vibration Attenuation Investigations on a Distributed Phononic Crystals Beam for Rubber Concrete Structures

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Chao Li ◽  
Sifeng Zhang ◽  
Liyong Gao ◽  
Wei Huang ◽  
Zhaoxin Liu
Keyword(s):  
Band Gap ◽  
Frequency Band ◽  
High Frequency ◽  
Concrete Beam ◽  
Vibration Isolation ◽  
Civil Engineering ◽  
Low Frequency ◽  
Band Gaps ◽  
Spring Force ◽  
Rubber Concrete

Locally resonant phononic crystals (LRPCs) beam is characterized by the band gaps; some frequency ranges within which flexural waves cannot propagate freely. So, the LRPCs beam can be used for noise or vibration isolation. In this paper, a LRPCs beam with distributed oscillators is proposed, and the general formula of band gaps and transmission spectrum are derived by the transfer matrix method (TMM) and spectrum element method (SEM). Subsequently, the parameter effects on band gaps are investigated in detail. Finally, a rubber concrete beam is designed to demonstrate the application of distributed LRPCs beam in civil engineering. Results reveal that the distributed LRPCs beam has multifrequency band gaps and the number of the band gaps is equal to that of the oscillators. Compared with others, the distributed LRPCs beam can reduce the stress concentration when subjected to vibration. The oscillator interval has no effect on the band gaps, which makes it more convenient to design structures. Individual changes of oscillator mass or stiffness affect the band gap location and width. When the resonance frequency of oscillator is fixed, the starting frequency of the band gap remains constant, and increasing oscillator mass of high-frequency band gap widens the high-frequency band gap, while increasing oscillator mass of low-frequency gap widens both high-frequency and low-frequency band gaps. External loads, such as the common uniform spring force provided by foundation in civil engineering, are conducive to the band gap, and when the spring force increases, all the band gaps are widened. Taken together, a configuration of LRPCs rubber concrete beam is designed, and it shows good isolation on the vibration induced by the railway. By the presented design flow chart, the research can serve as a reference for vibration isolation of LRPCs beams in civil engineering.

Idling Natural Characteristic Analysis of the Torsion Absorber with Dual Mass Flywheel

2011 ◽  
Vol 80-81 ◽  
pp. 860-864 ◽  
Author(s):  
Xian Jie Meng ◽  
Jun Wei Li
Keyword(s):  
Natural Frequency ◽  
Degrees Of Freedom ◽  
Natural Vibration ◽  
Low Frequency ◽  
Characteristic Analysis ◽  
Power Train ◽  
Torsion Vibration ◽  
Vibration Model ◽  
Natural Characteristic

Based on the analysis of two kinds of torsion absorber of automobile power train, a power train idling vibration model with nine degrees of freedom is established, the generalized Jacobin algorithms and the compiled Matlab procedures are used to calculate the idling natural frequency and idling natural vibration model. The results show that the dual mass flywheel torsion absorber can keep the power train from idling resonance compared with the clutch torsion absorber and play a good role in attenuating the low frequency torsion vibration of power train.

scholarly journals Analysis of the Vibration Isolation Effect of the Railway Rigid Sandwich Wall

2017 ◽  
Vol 11 (1) ◽  
pp. 121-130
Author(s):  
Sun Chenglong ◽  
Gao Liang
Keyword(s):  
Vibration Isolation ◽  
Low Frequency ◽  
Isolation Effect ◽  
Obvious Effect ◽  
Low Frequency Vibration ◽  
Vibration Model ◽  
Environmental Vibration ◽  
Sandwich Wall ◽  
Beijing Suburb ◽  
Environmental Isolation

The vibration isolation effect of the rigid sandwich wall was measured and the characteristics of time and frequency domain at low frequency was analyzed on the basis of the environmental isolation engineering of the railway in the Beijing suburb in this paper. The results indicated that environmental vibration significantly decreased after building the rigid sandwich walls. The vibration isolation efficiency of the rigid sandwich wall is respectively 0.32 and 0.46 at a distance of 35 meters and 40 meters away from railway center. It is obvious that a distance of 5 meters behind the vibration isolation barrier shows a more obvious vibration isolation effect than 10 meters. The vibration isolation barrier has an obvious effect in middle-high frequency (10~80 Hz) of the vibration, especially formed by sleeper spacing action rate (22.7 Hz). In addition, the effect is not obvious with a frequency below 10 Hz, such as the low frequency vibration formed by the moving axle load (7 Hz). In this paper, a vibration model of the earth-rigid sandwich wall was established. It also studied the effect of width, depth and position of the barrier on the vibration isolation, and provided the application condition and the setting requirement of key parameters for the rigid sandwich wall. These results provided the technical support for controlling projects of environmental vibration with rigid sandwich walls.

Control and Simulation on Vertical Vibration of Subway Rail via Magnetorheological Isolators

2012 ◽  
Vol 482-484 ◽  
pp. 1313-1316
Author(s):  
Rui Li ◽  
Li Min He ◽  
Xue Qin Li ◽  
Ke Long Chen
Keyword(s):  
Low Frequency ◽  
Vertical Vibration ◽  
Vibration System ◽  
Medium Frequency ◽  
Slab Track ◽  
Vibration Model ◽  
Active Vibration ◽  
Force Transmissibility ◽  
Stiffness Characteristics ◽  
Isolation Performance

A semi-active vibration system via magnetorheological (MR) isolators can contribute to enhance isolation performance. In this study, a vertical vibration model of subway rail via MR isolators was proposed. The adjustable damping and stiffness characteristics of isolator were also analyzed. Based on a floating slab track (FST) isolation model, a variable domain fuzzy control system was proposed to decrease the vertical vibration force. The results simulated in MATLAB indicate that compared with passive isolators, FST system via MR isolators decease vertical vibration force transmissibility ratio to 40% at low frequency (15Hz) and to 31% at medium frequency (30Hz).

Research on Processing Parameters of Large Lathe Bed's Vibratory Stress Relief

2010 ◽  
Vol 455 ◽  
pp. 454-457
Author(s):  
Jian Xi Yang ◽  
Y.Z. Cheng ◽  
Feng Kui Cui ◽  
Hong Yu Xu
Keyword(s):  
Residual Stress ◽  
Natural Vibration ◽  
Low Frequency ◽  
Stress Relief ◽  
Processing Parameters ◽  
Exciting Force ◽  
Natural Mode ◽  
Technological Parameters ◽  
Vibration Model ◽  
Exciting Frequency

In order to enhance the actual effect of vibration aging on large lathe bed and optimize it, many technological parameters of vibration aging will be discussed in this paper, including exciting force, exciting frequency and exciting point, etc. Finite element method is used to analyze the casting stress distribution and natural mode of vibration of a large lathe bed. After the analysis, it is found that the distribution of the residual stress of the lathe bed is extremely uneven. By analyzing parameters of the natural vibration model and the exciting force as well as the exciting point, a reasonable parameter will be got when the lathe bed is vibrating. The “Selecting low-frequency to avoid torsion mode” which reduces the deformation to bed caused by the residual stress, was proposed. The parameters have been proved effective through experiment, and the proposed approach can be used in the research of vibratory stress relief.

Vibration Modeling of Arc-Based Cantilevers for Energy Harvesting Applications

2014 ◽  
Vol 1 (1-2) ◽  
Author(s):  
Daniel J. Apo ◽  
Mohan Sanghadasa ◽  
Shashank Priya
Keyword(s):  
Energy Harvesting ◽  
Low Frequency ◽  
Substrate Thickness ◽  
Cantilever Beams ◽  
Vibration Energy Harvesting ◽  
Low Frequency Vibration ◽  
Vibration Model ◽  
Bending Mode ◽  
Out Of Plane ◽  
Tip Mass

AbstractCantilever beams are widely used for designing transducers for low-frequency vibration energy harvesting. However, in order to keep the dimensions within reasonable constraints, a large tip mass is generally required for reducing the resonance frequency below 100 Hz which has adverse effect on the reliability. This study provides a breakthrough toward realizing low-frequency micro-scale transduction structures. An analytical out-of-plane vibration model for standalone arc-based cantilever beams was developed that includes provisions for shear and rotary inertia, multidirectional arcs, and multiple layers. The model was applied to a multilayered cantilever beam (10-mm wide and 0.1-mm thick) composed of three arcs, and the results indicate that the fundamental bending mode of the beam was 38 Hz for a silicon substrate thickness of 100 μm. The model was validated with modal experimental results from an arc-based cantilever made out of aluminum.

scholarly journals Improvement of transmission loss of bellows through thickness improvement and structural modification

2021 ◽  
Vol 13 (9) ◽  
pp. 168781402110496
Author(s):  
Hee-Min Noh
Keyword(s):  
Simple Model ◽  
Transmission Loss ◽  
Layer Structure ◽  
Low Frequency ◽  
Frequency Region ◽  
Test Results ◽  
Noise Performance ◽  
Actual Performance ◽  
Low Transmission ◽  
Vibration Model

The bellows of the vehicle are vulnerable to noise because of the low transmission loss among the components. Therefore, in this study, we modified the thickness and the structure of the bellows to improve transmission loss. Based on the impedance tube test, the transmission loss of the silicon rubber specimen – the main material of the bellows – was analyzed; the results confirmed low transmission loss in the low-frequency region. An analysis of the natural vibration model of the simple model indicated that in the low-frequency region of the bellows, a number of vibrations occurred because of the vibration of the outer and inner components. Accordingly, to improve transmission loss, the improvement introduced by varying the thickness was analyzed, and the results confirmed that the noise performance improved by more than 3 dB for a thickness of 3.5 mm in the double-layer structure. In addition, the transmission loss improved in the low-frequency region after acoustic-structure coupling analysis was performed based on a simple model. To compare the actual performance between the existing and improved bellows, a noise comparison test was performed. The test results confirm that the existing noise reduction index improved by 3 dB from 30 to 33 dB when the thickness was increased to 3.5 mm; in the frequency domain, the highest noise performance was improved with an improvement of 5.6 dB at 160 Hz.

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