Dynamic Properties of MWNTS/Epoxy Nanocomposite Beams

2007 ◽  
Vol 334-335 ◽  
pp. 709-712 ◽  
Author(s):  
Meng Kao Yeh ◽  
Tsung Han Hsieh
Keyword(s):  
Dynamic Properties ◽  
Damping Ratio ◽  
Free Vibration Analysis ◽  
Mode Shapes ◽  
Laser Sensor ◽  
Vibration Source ◽  
Weight Percentage ◽  
Epoxy Nanocomposite ◽  
Fixed Base ◽  
Half Power

The dynamic properties of multi-walled carbon nanotubes (MWNTS)/epoxy nanocomposite beams were investigated experimentally and numerically. The MWNTs/epoxy nanocomposite beams were fabricated by hot press method. In experiment, the dynamic properties of the nanocomposite beams, such as natural frequency, and damping ratio, were obtained. A shaker was used to provide the vibration source at the fixed base of the specimens. The vibration signals of the nanocomposite beams were detected by a laser sensor, and the frequency responses were obtained by a computer-aided signal analyzer. The half power method was used to find the damping ratios of the nanocomposite beams for each mode. In analysis, the mechanical properties of MWNTs/epoxy nanocomposites were obtained and used in the free vibration analysis by the finite element method. The natural frequencies and mode shapes of the nanocomposite beams were calculated numerically. The effect of the weight percentage of MWNTs on the dynamic properties of the nanocomposite beams was investigated. The numerical results were found to be in good agreement with the experimental ones.

Dynamic and Vibration Analysis of a SAR Membrane Antenna

2007 ◽  
Author(s):  
Yu Shen ◽  
Wanping Zheng ◽  
Xiaoyun Wang
Keyword(s):  
Attitude Control ◽  
Natural Frequencies ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Mode Shapes ◽  
Base Excitation ◽  
Control Torque ◽  
Satellite Attitude ◽  
Satellite Attitude Control ◽  
Low Mass

Synthetic Aperture Radar (SAR) membrane antennas have attracted much attention for their low mass, small stowed volume, large gain and high resolution. To deploy a membrane antenna requires a deployable support structure providing deployment and rigid support after it is fully deployed. A membrane antenna’s vibration may be caused by the disturbance of the satellite attitude-control torque in spacecraft, and it is determined by the mechanical properties of the membrane and its in-plane tension loads. In this paper, the dynamic properties of the deployable structure are studied with ADAMS when the flexibility of the frames is considered. The mode shapes and the natural frequencies of the membrane are analyzed with ABAQUS when the pre-tension loads provided by the tension cable are changed. The random response of the membrane subjected to the base excitation is studied for different tension forces and damping ratios. This work provides a guideline for the vibration control of the membrane by controlling its tension force or damping ratio.

Vibration Characteristics Analysis of Aeroengine Composite Blade

2012 ◽  
Vol 583 ◽  
pp. 57-61
Author(s):  
Qiang Yang ◽  
Ke Qiang Fang ◽  
Chuang Shao
Keyword(s):  
Laser Scanning ◽  
Damping Ratio ◽  
Dynamic Test ◽  
Vibration Characteristics ◽  
Mode Shapes ◽  
Modal Parameter ◽  
Blade Vibration ◽  
Nodal Lines ◽  
Composite Blade ◽  
Half Power

In order to validate the dynamic response and the dynamic stress distribution of the blade, EMA and FEM were performed to study the vibration characteristics. A non-contact laser scanning viberometer was used to measure the blade modal response. After the signal process of the response, the natural frequencies, mode shapes and their nodal lines can be obtained by the modal parameter identification method. And the blade modal damping ratio can be calculated from its frequency response function (FRF), which was obtained during the test, by the half-power method. Based on the test results, a simplified computational model was established by layup method, and after modification, the error of FEM results and EMA results was less than 5%. So the blade vibration characteristics and its finite element prediction model were obtained by the two methods combined, which would laid a foundation for the dynamic test and the vibration fatigue life prediction of the blade.

Experimental and numerical investigation on dynamic parameters of broaching machine

2015 ◽  
Vol 231 (10) ◽  
pp. 1907-1920
Author(s):  
Shenshun Ying ◽  
Shiming Ji ◽  
Yangyu Wang ◽  
Zhixin Li ◽  
Lvgao Lin ◽  
...  
Keyword(s):  
Modal Analysis ◽  
Natural Frequencies ◽  
Dynamic Properties ◽  
Structural Parameters ◽  
Damping Ratio ◽  
Experimental Results ◽  
Mode Shapes ◽  
Fe Model ◽  
Dynamic Parameters ◽  
Machine Structure

Dynamic properties of the whole broaching machine structure greatly contribute to the broaching quality and efficiency. However, it is hard to measure the dynamic parameters because they will change during operation compared with the static results from classic experimental modal analysis. This study is to examine the dynamic parameters of broaching machine LG7120KT using both the numerical finite element (FE) method and the experimental operational modal analysis (OMA). Firstly, FE analysis model of the broaching machine with the real dimension is constructed and calculated. Second, experimental results are obtained from OMA in practical broaching process, which can be used to identify steady-state modes. Modal parameters including mode shapes, damping ratio, and natural frequencies are examined, using both LMS SCADAS III-305 system and PolyMAX method in OMA. The numerical and experimental results show high agreement in their calculated natural frequencies. From the modal analysis results, it is also found the vibration normal to cutting direction can be greatly reduced by adjusting broaching speed. From the topology optimization result based on the already correlated FE model, we redesigned a lightweight machine structure with a better dynamic performance, due to its lower displacement of broaching machine at force point and its higher first-order natural frequency. The experimental and numerical results in this paper help to design the structural parameters of broaching machine and propose a better broaching process.

Processing forced vibration test records of structural systems using the analytic signal

2020 ◽  
pp. 107754632095792
Author(s):  
Ozan Cem Celik ◽  
Hakkı Polat Gülkan
Keyword(s):  
Reinforced Concrete ◽  
Forced Vibration ◽  
Dynamic Properties ◽  
Analytic Signal ◽  
Mode Shapes ◽  
Vibration Test ◽  
Structural Systems ◽  
Vibration Source ◽  
Response Curves ◽  
Forced Vibration Test

This article presents the use of the analytic signal procedure for processing the large volume of structural vibration data recorded in forced vibration tests. The analytic signal facilitates the computationally laborious task of extracting the steady-state amplitude for each response measure of interest from the recorded accelerations throughout the building at each operated frequency of the forced vibration source. The implementation of the signal processing procedure introduced here is illustrated in deriving the acceleration–frequency response curves from the forced vibration test of the first permanently instrumented building in Turkey. This reinforced concrete building, subsequently strengthened with cast-in-place reinforced concrete infill shear walls, is located in close proximity to the North Anatolian Fault. Later, system identification of the building yields the in situ structural system dynamic properties for the first translational and torsional vibration modes, which are compared with those identified from the ambient vibrations of the building recorded following its forced vibration test. The analytic signal procedure is a convenient tool for the rapid and correct derivation for mode shapes and associated frequencies and damping ratios from forced vibration testing of structural systems.

Effect of Crack Orientation on Laminated CFRP Composites Using Vibration and Numerical Analysis

2021 ◽  
Vol 79 (11) ◽  
pp. 1081-1093
Author(s):  
Essam Moustafa ◽  
Khalid Almitani ◽  
Hossameldin Hussein
Keyword(s):  
Composite Structures ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Composite Plates ◽  
Mode Shapes ◽  
Crack Orientation ◽  
Test Plate ◽  
Cfrp Composites ◽  
Cfrp Composite ◽  
Vibration Tests

Crack orientation, a critical parameter, significantly affects the dynamic properties of composite structures. Experimental free vibration tests were conducted on carbon fiber–reinforced polymer (CFRP) composite plates at room temperature with different crack orientations. Dynamic properties such as damping ratio, natural frequency, and storage modulus were measured using a four-channel dynamic pulse analyzer. Multi-sensors were mounted on the test plate to pick up the vibration signals. Experimental modal analysis was performed to identify the first three mode shapes of the defective plates. A numerical model using ANSYS software was developed via parametric investigation to predict the correlation between crack orientation and resonant frequencies with corresponding mode shapes. The orientation of the introduced cracks had a significant effect on the dynamic properties of CFRP composites. Vertical cracks had the most significant influence on the eigenvalues of the mode shape frequencies. Furthermore, the damping ratio was an effective method to detect the cracks in CFRP composites.

scholarly journals Evaluation of Dynamic Properties of Sodium-Alginate-Reinforced Soil Using A Resonant-Column Test

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2743
Author(s):  
Seongnoh Ahn ◽  
Jae-Eun Ryou ◽  
Kwangkuk Ahn ◽  
Changho Lee ◽  
Jun-Dae Lee ◽  
...  
Keyword(s):  
Shear Modulus ◽  
Sodium Alginate ◽  
Shear Failure ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Reinforced Soil ◽  
Resonant Column ◽  
Column Test ◽  
Alginate Solution ◽  
Resonant Column Test

Ground reinforcement is a method used to reduce the damage caused by earthquakes. Usually, cement-based reinforcement methods are used because they are inexpensive and show excellent performance. Recently, however, reinforcement methods using eco-friendly materials have been proposed due to environmental issues. In this study, the cement reinforcement method and the biopolymer reinforcement method using sodium alginate were compared. The dynamic properties of the reinforced ground, including shear modulus and damping ratio, were measured through a resonant-column test. Also, the viscosity of sodium alginate solution, which is a non-Newtonian fluid, was also explored and found to increase with concentration. The maximum shear modulus and minimum damping ratio increased, and the linear range of the shear modulus curve decreased, when cement and sodium alginate solution were mixed. Addition of biopolymer showed similar reinforcing effect in a lesser amount of additive compared to the cement-reinforced ground, but the effect decreased above a certain viscosity because the biopolymer solution was not homogeneously distributed. This was examined through a shear-failure-mode test.

scholarly journals Identification of Dynamic Parameters of Pedestrian Walking Model Based on a Coupled Pedestrian–Structure System

2021 ◽  
Vol 11 (14) ◽  
pp. 6407
Author(s):  
Huiqi Liang ◽  
Wenbo Xie ◽  
Peizi Wei ◽  
Dehao Ai ◽  
Zhiqiang Zhang
Keyword(s):  
Negative Correlation ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Field Testing ◽  
The Body ◽  
Structural Vibration ◽  
Pedestrian Dynamics ◽  
Structure Interaction ◽  
Mass Spring ◽  
Stiffness And Damping

As human occupancy has an enormous effect on the dynamics of light, flexible, large-span, low-damping structures, which are sensitive to human-induced vibrations, it is essential to investigate the effects of pedestrian–structure interaction. The single-degree-of-freedom (SDOF) mass–spring–damping (MSD) model, the simplest dynamical model that considers how pedestrian mass, stiffness and damping impact the dynamic properties of structures, is widely used in civil engineering. With field testing methods and the SDOF MSD model, this study obtained pedestrian dynamics parameters from measured data of the properties of both empty structures and structures with pedestrian occupancy. The parameters identification procedure involved individuals at four walking frequencies. Body frequency is positively correlated to the walking frequency, while a negative correlation is observed between the body damping ratio and the walking frequency. The test results further show a negative correlation between the pedestrian’s frequency and his/her weight, but no significant correlation exists between one’s damping ratio and weight. The findings provide a reference for structural vibration serviceability assessments that would consider pedestrian–structure interaction effects.

scholarly journals Multi-Scale Study of The Small-Strain Damping Ratio of Fiber-Sand Composites

Polymers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2476
Author(s):  
Haiwen Li ◽  
Sathwik S. Kasyap ◽  
Kostas Senetakis
Keyword(s):  
Dynamic Properties ◽  
Wide Spectrum ◽  
Damping Ratio ◽  
Polypropylene Fiber ◽  
Small Strain ◽  
Treatment Method ◽  
Fiber Content ◽  
Polypropylene Fibers ◽  
Test Results ◽  
Fiber Reinforced

The use of polypropylene fibers as a geosynthetic in infrastructures is a promising ground treatment method with applications in the enhancement of the bearing capacity of foundations, slope rehabilitation, strengthening of backfills, as well as the improvement of the seismic behavior of geo-systems. Despite the large number of studies published in the literature investigating the properties of fiber-reinforced soils, less attention has been given in the evaluation of the dynamic properties of these composites, especially in examining damping characteristics and the influence of fiber inclusion and content. In the present study, the effect of polypropylene fiber inclusion on the small-strain damping ratio of sands with different gradations and various particle shapes was investigated through resonant column (macroscopic) experiments. The macroscopic test results suggested that the damping ratio of the mixtures tended to increase with increasing fiber content. Accordingly, a new expression was proposed which considers the influence of fiber content in the estimation of the small-strain damping of polypropylene fiber-sand mixtures and it can be complementary of damping modeling from small-to-medium strains based on previously developed expressions in the regime of medium strains. Additional insights were attempted to be obtained on the energy dissipation and contribution of fibers of these composite materials by performing grain-scale tests which further supported the macroscopic experimental test results. It was also attempted to interpret, based on the grain-scale tests results, the influence of fiber inclusion in a wide spectrum of properties for fiber-reinforced sands providing some general inferences on the contribution of polypropylene fibers on the constitutive behavior of granular materials.

Research on Damping Properties of TiN Coating Prepared with Arc Ion Plating

2012 ◽  
Vol 184-185 ◽  
pp. 1167-1170
Author(s):  
Guang Yu Du ◽  
Zhen Tan ◽  
Kun Liu ◽  
Hao Chai ◽  
De Chun Ba
Keyword(s):  
Chemical Composition ◽  
Surface Morphology ◽  
Loss Factor ◽  
Steel Substrate ◽  
Damping Ratio ◽  
Energy Dispersive Spectrometer ◽  
Tin Coating ◽  
Arc Ion Plating ◽  
Ion Plating ◽  
Half Power

In this paper TiN coating was prepared on stainless steel substrate using arc ion plating technique. The coating samples’ phases, surface morphology, micro-determination chemical composition, loss factor and damping ratio were tested. The phases of TiN coating were determined by X-ray diffraction (XRD) technique. The surface morphology and chemical composition of the TiN coating were analyzed by scanning electron microscope (SEM) and Energy Dispersive Spectrometer (EDS), respectively. The damping performance of the samples was measured by hammering activation according half power bandwidth method. The loss factor or damping ratio of samples were obtained according frequency response curve. The results showed that damping performance of samples was considerably improved by TiN coatings.

Measured natural periods of concrete shear wall buildings: insights for the design of Canadian buildings

2012 ◽  
Vol 39 (8) ◽  
pp. 867-877 ◽  
Author(s):  
Damien Gilles ◽  
Ghyslaine McClure
Keyword(s):  
Seismic Analysis ◽  
Dynamic Properties ◽  
Response Spectrum ◽  
Shear Wall ◽  
Mode Shapes ◽  
Design Stage ◽  
Base Shear ◽  
Period Equation ◽  
Input Load ◽  
Structural Engineers

Structural engineers routinely use rational dynamic analysis methods for the seismic analysis of buildings. In linear analysis based on modal superposition or response spectrum approaches, the overall response of a structure (for instance, base shear or inter-storey drift) is obtained by combining the responses in several vibration modes. These modal responses depend on the input load, but also on the dynamic characteristics of the building, such as its natural periods, mode shapes, and damping. At the design stage, engineers can only predict the natural periods using eigenvalue analysis of structural models or empirical equations provided in building codes. However, once a building is constructed, it is possible to measure more precisely its dynamic properties using a variety of in situ dynamic tests. In this paper, we use ambient motions recorded in 27 reinforced concrete shear wall (RCSW) buildings in Montréal to examine how various empirical models to predict the natural periods of RCSW buildings compare to the periods measured in actual buildings under ambient loading conditions. We show that a model in which the fundamental period of RCSW buildings varies linearly with building height would be a significant improvement over the period equation proposed in the 2010 National Building Code of Canada. Models to predict the natural periods of the first two torsion modes and second sway modes are also presented, along with their uncertainty.

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