Estimation of damping ratio of silicone rubber using half power bandwidth method

2021 ◽  
Author(s):  
Prahalad S. Badkar ◽  
M.M. Benal
Keyword(s):  
Silicone Rubber ◽  
Damping Ratio ◽  
Half Power

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.

scholarly journals Damping Measurements in Tube Bundles Subjected to Two-Phase Cross Flow

2006 ◽  
Author(s):  
Joaquin E. Moran ◽  
David S. Weaver
Keyword(s):  
Flow Regime ◽  
Void Fraction ◽  
Mass Flux ◽  
Damping Ratio ◽  
Logarithmic Decrement ◽  
Working Fluid ◽  
Exponential Fitting ◽  
Two Phase ◽  
Tube Bundles ◽  
Half Power

An experimental study was conducted to investigate two-phase damping in tube arrays. The objective was to compare different measurement methodologies in order to obtain a more reliable damping estimate. This will allow for improved guidelines related to failures due to fluidelastic instability in tube bundles. The methods compared were the traditionally used half-power bandwidth, the logarithmic decrement and an exponential fitting to the tube decay response. The working fluid used was Refrigerant 11 (Freon), which better models the real steam-water problem, as it allows for phase change. The void fraction was measured using a gamma densitometer, introducing an improvement over the traditional Homogeneous Equilibrium Model (HEM) in terms of velocity and density predictions. The results obtained by using the half-power bandwidth method agree with data previously reported for two-phase flow. The experiments showed that the half-power bandwidth produces higher damping values than the other two, but only up to a certain void fraction. After that point, the results obtained from the three methods are very similar. The exponential fitting proved to be more consistent than the logarithmic decrement, and it is not as sensitive as the half-power bandwidth to the frequency shifting caused by the change in added mass around the tube. By plotting the damping ratio as a function of void fraction, pitch mass flux and flow regime, we were able to verify that damping is more dependent on void fraction and flow regime than on mass flux.

Experimental Damping of a Heat Exchange Tube With a Large Number of Supports in Air and Water

2017 ◽  
Author(s):  
Tae-Jung Park ◽  
Chang-Hoon Ha ◽  
Min-Ki Cho ◽  
Heung Seok Kang ◽  
Kang Hee Lee
Keyword(s):  
Steam Generator ◽  
Nuclear Power ◽  
Large Scale ◽  
Damping Ratio ◽  
Water Environment ◽  
Random Force ◽  
Flow Induced Vibration ◽  
Heat Exchange Tube ◽  
Half Power ◽  
Support Grid

The flow induced vibration occurs frequently in a steam generator in the nuclear power plant. The large-scale steam generator has a large number of tube supports whose cell has rhombus-type shape, and there is a tiny clearance between tube and its support grid. The damping is very complex because of non-linearity and randomness. The experiment for damping was performed to investigate it with a number of 13 support spans both in air and water environment. The lower part of multi-span fixture was excited by root-mean-square random force with the range of 1∼10 newton to get the frequency response function. The half-power bandwidth method was applied to obtain the damping ratio. The sensitivity of a number of spans was investigated in the range of 9 ∼ 13. In addition, the damping was reviewed from a comparison with Pettigrew [1∼4] and ASME B&PV Code [5].

Experimental study of parameters influencing the damping of particulate, fibre-reinforced, hybrid, and sandwich composites

2020 ◽  
Vol 111 (8) ◽  
pp. 688-697
Author(s):  
Zuzana Murčinková ◽  
Jozef Živčák ◽  
Jozef Zajac
Keyword(s):  
Composite Materials ◽  
Volume Fraction ◽  
Damping Ratio ◽  
Logarithmic Decrement ◽  
Sandwich Composites ◽  
Damping Properties ◽  
Different Types ◽  
Typical Time ◽  
Half Power

Abstract In this study, we focus on the experimental determination of damping expressed by logarithmic decrement, damping ratio, and loss factor of particulate, continuous- and discontinuous- fibre reinforced, hybrid, and sandwich composites using the free vibration decay effect evaluated using the logarithmic decrement and half-power bandwidth methods. Composite materials with damping properties of magnitude several orders higher than that of traditional engineering materials are well known. However, in one study, we present different types of composite materials with different damping properties depending on various parameters such as ply angle, volume fraction, material configuration, reinforcement geometry, temperature, etc., which provide varied options to design the material arrangement of dynamically loaded components to maximize damping. Moreover, in this study, we determine typical time and frequency domain curves for individual types of analysed composites.

Comparison of damping parameters based on the half-power bandwidth methods of viscous and hysteretic damping models

2021 ◽  
pp. 107754632110546
Author(s):  
Panxu Sun ◽  
Dongwei Wang
Keyword(s):  
Loss Factor ◽  
Damping Ratio ◽  
Relative Difference ◽  
Structural Damping ◽  
Application Condition ◽  
Comparison Results ◽  
First Choice ◽  
Hysteretic Damping ◽  
Approximate Relationship ◽  
Half Power

The half-power bandwidth method is usually used to calculate structural damping parameters by frequency response function (FRF). In this note, the half-power bandwidth methods for the displacement FRF, the velocity FRF, and the acceleration FRF are proposed based on viscous and hysteretic damping models, respectively. Comparison results show that the application conditions of half-power bandwidth methods for the displacement and acceleration FRFs are limited. They can only be used to calculate the small damping ratio/loss factor. The application condition of half-power bandwidth method for the velocity FRF is not limited. It can be used to calculate the large or small damping ratio/loss factor, which should be the first choice for calculating damping parameters. Besides, when the damping ratio is less than 0.2546 or the loss factor is less than 0.5658, the relative difference between the loss factor and twice the damping ratio is less than 10%. With the increase of the damping ratio or loss factor, the relative difference will increase rapidly, and the approximate relationship is no longer applicable.

An Analysis of Higher Order Effects in the Half Power Method for Calculating Damping

2010 ◽  
Vol 78 (1) ◽  
Author(s):  
Ivan Wang
Keyword(s):  
Frequency Response ◽  
Classical Method ◽  
Damping Ratio ◽  
Higher Order ◽  
Order Effects ◽  
Power Method ◽  
Response Curves ◽  
Third Order ◽  
Truncation Errors ◽  
Half Power

The half power method is a technique commonly used for calculating the system damping using frequency response curves. Past derivations typically assume a small damping ratio but do not keep track of the order of magnitude when simplifying results and focus mainly on displacement frequency response curves. This paper provides two separate and rigorous derivations of the half power bandwidth for displacement and acceleration frequency response functions. The exact expressions are simplified systematically using binomial expansions to include third order effects. The third order and classical approximations are compared with the exact expressions, and the truncation errors are presented for both displacement and acceleration cases. The high order effects are more apparent and the truncation errors are greater for the acceleration case. The classical method is sufficiently accurate for many practical cases where the damping ratio is less than 0.1 but higher order corrections may be used to reduce truncation error for systems where the damping ratio is higher.

Resin Concrete Specimens Attenuation Characteristics Research

2011 ◽  
Vol 141 ◽  
pp. 478-482
Author(s):  
Hong Gang Ding ◽  
Ze Yu Weng ◽  
Hong Wu You ◽  
Bo Lu ◽  
Xue Zhe Tang
Keyword(s):  
Cast Iron ◽  
Machine Tool ◽  
Dynamic Characteristics ◽  
Manufacturing Process ◽  
Response Curve ◽  
Damping Ratio ◽  
Frequency Response Curve ◽  
Amplitude Frequency Response ◽  
Half Power ◽  
Attenuation Characteristics

This paper introduces a method of manufacturing process of resin concrete, made three tubular cast-iron specimens filled with resin concrete. This paper detected the amplitude-frequency response curve of specimens in experimental method, and calculated the damping ratio of specimens through half power bandwidth method. The damping ratio of specimens is compared. It provided a good reference for the design of the machine tool on the dynamic characteristics.

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.

Cement-Based Composite with Carbon Nanotubes Reinforcement Tailored for Structural Damping

2010 ◽  
Vol 150-151 ◽  
pp. 526-529
Author(s):  
Jian Lin Luo ◽  
Zhong Dong Duan ◽  
Tie Jun Zhao ◽  
Qiu Yi Li
Keyword(s):  
Carbon Nanotubes ◽  
Forced Vibration ◽  
Ultrasonic Treatment ◽  
Damping Ratio ◽  
Damping Capacity ◽  
Structural Damping ◽  
Shear Mixing ◽  
Multi Walled Carbon Nanotubes ◽  
Half Power ◽  
Walled Carbon Nanotubes

Cement-based composites filled with some multi-walled carbon nanotubes (MWNTs) (MWNT/CC) were fabricated using surfactant enwrapping, ultrasonic treatment, and subsequently intensive shear mixing. The damping capacities of the cured nanocomposites were characterized with forced vibration testing and half-power bandwidth identification method. Results show that, the MWNTs can greatly enhance the structural damping capacity of the MWNT/CC beam with balanced strength reinforcement. There exists 44.5%, 10% increase in the damping ratio, and fundamental frequency of the MWNT/CC with 1.0 wt% MWNTs addition, along with strength reinforcement, as compared to the reference, respectively.

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.

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