A MEASUREMENT OF ULTRASONIC ATTENUATION COEFFICIENT BY FREQUENCY RESPONSE IN STEELS WITH DIFFERENT GRAIN SIZES

2003 ◽  
Vol 26 (4) ◽  
pp. 389-402
Author(s):  
Kyung-Cho Kim
Keyword(s):  
Frequency Response ◽  
Attenuation Coefficient ◽  
Evaluation Method ◽  
Ultrasonic Attenuation ◽  
Wave Length ◽  
Structural Behavior ◽  
Response Property ◽  
Sound Waves ◽  
Grain Sizes ◽  
Plate Specimen

A new evaluation method of ultrasonic attenuation in materials is proposed based on the frequency response property of the material evaluated by employing the sound impulse of a wide frequency band. Borrowing from ordinary system theory, the material to be tested is considered to have a characteristic impulse response, representing its micro-structural non-uniformities and thus resulting in the sound attenuation of the material. The concept is resumed as an attenuation system that simulates the material’s micro-structural behavior. Experimental results on a series of specimens, having different grain sizes but all made of a single austenitic stainless steel, showed that the attenuation could properly be evaluated from a single bottom echo in a plate specimen. The attenuation coefficient α, was corrlated in this case to the grain size, D, by the equation, αD=H(πD/λ)n, where λ is wave length and H and n are constants. It was also shown that the micro structural change of materials could be evaluated by the energy loss of sound waves passing through the attenuation systems.

scholarly journals Study on measurement of sound attenuation coefficient in bubble wake by pool

2020 ◽  
Vol 206 ◽  
pp. 03013
Author(s):  
Jing Han ◽  
Shuai Lv ◽  
Zhongpeng Wu ◽  
Mingwei Zhang ◽  
Jin Bai
Keyword(s):  
Attenuation Coefficient ◽  
Bubble Size ◽  
Sound Attenuation ◽  
Signal Frequency ◽  
Sound Waves ◽  
Air Inlet ◽  
Stimulation Tests ◽  
Measurement Experiment ◽  
Small Bubbles ◽  
Attenuation Characteristics

In this paper, bubbles are generated by controlling the air inlet volume of the ceramic tube array with a gas divider valve. Stimulation tests of sound attenuation characteristics of the wake of bubbles in a laboratory pool are performed. A measurement experiment of sound attenuation coefficient was carried out in the case of still water and bubbles with different particle sizes. The signal frequency is 20-200kHz. Through experimental research, it is found that the existence of bubbles makes the sound attenuation coefficient significantly larger. And the attenuation coefficient is related to the frequency of the sound waves and the size of the bubbles. At the same frequency, the larger the bubble size , the larger the attenuation coefficient will be. When the bubble size is constant, the attenuation of the acoustic signal in small bubbles will change greatly below 50kHz. Above 50kHz, the attenuation coefficient changes relatively smoothly and the fluctuation is small. In the case of medium and large bubbles, the fluctuation of the attenuation coefficient becomes larger than that in the small bubbles. Finally, the theoretically calculated sound attenuation coefficient is compared with the experimentally measured results. And the change trends of the two results are basically the same.

Evaluation of Thermal Degradation of 2.25Cr-1Mo Steel by High Frequency Ultrasonic Attenuation Measurement

2005 ◽  
Vol 475-479 ◽  
pp. 257-260 ◽  
Author(s):  
Jai Won Byeon ◽  
C.S. Kim ◽  
S.I. Kwun ◽  
S.J. Hong
Keyword(s):  
Attenuation Coefficient ◽  
High Frequency ◽  
Ultrasonic Attenuation ◽  
Attenuation Coefficients ◽  
Low Frequencies ◽  
High Frequencies ◽  
Noticeable Increase ◽  
Mean Size ◽  
Longitudinal Ultrasonic Wave ◽  
Degradation Time

It was attempted to assess nondestructively the degree of isothermal degradation of 2.25Cr-1Mo steel by using high frequency longitudinal ultrasonic wave. Microstructural parameter (mean size of carbides), mechanical property (Vickers hardness) and ultrasonic attenuation coefficient were measured for the 2.25Cr-1Mo steel isothermally degraded at 630°C for up to 4800 hours in order to find the correlation among these parameters. The ultrasonic attenuation coefficients at high frequencies (over 35MHz) were observed to increase rapidly in the initial 1000 hours of degradation time and then slowly thereafter, while the ones at low frequencies showed no noticeable increase. Ultrasonic attenuation at high frequencies increased as a function of mean size of carbides. Ultrasonic attenuation coefficient was found to have a linear correlation with the hardness, and suggested accordingly as a potential nondestructive evaluation parameter for assessing the mechanical strength reduction of the isothermally degraded 2.25Cr-1Mo steel.

scholarly journals On the problem of the electrified disc

1947 ◽  
Vol 8 (1) ◽  
pp. 14-19 ◽  
Author(s):  
E. T. Copson
Keyword(s):  
External Field ◽  
Gravitational Potential ◽  
Electrostatic Field ◽  
Surface Density ◽  
Wave Length ◽  
Circular Disc ◽  
Sound Waves ◽  
Total Potential ◽  
Induced Charge ◽  
Lord Kelvin

When a perfectly conducting uniform thin circular disc is kept at a potential V0 in an external electrostatic field of potential Φ, electric charge is induced on the surface of the disc; the problem is to find the surface-density σ of this induced charge and its potential V so that the total potential V + Φ has the constant value V0 on the surface of the disc. This problem was first discussed by Green in 1832, and the solution in the case when there is no external field was deduced by Lord Kelvin from the known formula for the gravitational potential of an elliptic homoeoid. The problem is still of interest since similar ideas occur in the theory of diffraction by a circular disc and in the theory of the generation of sound waves by a vibrating disc when the wave-length is large compared with the radius of the disc.

scholarly journals 79. Radio emission from the moon and the nature of its surface

1957 ◽  
Vol 4 ◽  
pp. 406-407 ◽  
Author(s):  
V. S. Troitzky ◽  
S. E. Khaikin
Keyword(s):  
Radio Emission ◽  
Attenuation Coefficient ◽  
Wave Length ◽  
Degree Of Polarization ◽  
Lunar Phase ◽  
Radio Waves ◽  
The Moon ◽  
Subsolar Point ◽  
Image Position ◽  
Academy Of Sciences

A theoretical study of the integral radio emission of the moon, measured at the wave-length of 3·2 cm. (Zelinskaja and Troitzky[1]; Kajdanovsky, Turusbekov and Khaikin[2]), was carried out at the Gorky radio astronomical station ‘Zimenky’ and at the Physical Institute of the Academy of Sciences of the U.S.S.R. The following expression for the average radio temperature of the entire lunar disk, as a function of the lunar phase, Ωt, was obtained (Troitzky, 1954) [3]: Here tan ξ = δ/(1 + δ) and δ = β/κ, where β is the attenuation coefficient of the thermal wave, κ the power attenuation coefficient of the radio wave. Further, Tm = 374°K. is the temperature of the subsolar point, Tn is the temperature at the lunar midnight, Θ = Tm – Tn and k0 is the reflexion coefficient of radio waves for vertical incidence (k0 ≈ 0–1). The numerical coefficients in equation (1) were obtained as a result of averaging the Fresnel reflexion coefficients over the whole disk. The degree of polarization of the total radio emission was calculated and was found to be about 4 %.

Recent Advances in Gravelly Soils Liquefaction Evaluation

2011 ◽  
Vol 90-93 ◽  
pp. 1443-1446
Author(s):  
Long Qing Hou ◽  
Ai Fei Li ◽  
Hong Mei Xu ◽  
Chun Feng He ◽  
Peng Hu
Keyword(s):  
Wenchuan Earthquake ◽  
Evaluation Method ◽  
Large Diameter ◽  
Penetration Test ◽  
2008 Wenchuan Earthquake ◽  
Moderate Density ◽  
Grain Sizes ◽  
Triaxial Apparatus ◽  
The Wenchuan Earthquake ◽  
Gravelly Soils

Many gravelly soils liquefied cases history especially in the 2008 Wenchuan earthquake warn that loose to moderate density of gravels have much potential to liquefy under a given earthquake shaking. The large diameter triaxial apparatus is a relative feasible means to explore the liquefaction mechanism of gravelly soils to some extent. Becker penetration test (BPT) could be droved hrough gravelly soils layer, but BPT was not directly correlated with field behavior. Because of a wider range of grain sizes than those reported from previous earthquakes, gravels characteristics liquefied in the Wenchuan earthquake are representative and universal. The gravels liquefaction evaluation method developed from the Wenchuan earthquake should be feasible for worldwide use. The recent and ongoing developments in gravels liquefaction was highlighted

543: Ultrasonic attenuation coefficient of the cervix in women receiving ultrasound indicated cerclage: a pilot study

2016 ◽  
Vol 214 (1) ◽  
pp. S292-S293
Author(s):  
Yvette Cordova ◽  
Aiguo Han ◽  
William D. O'Brian ◽  
Samadh H. Ravangard ◽  
Michelle A. Kominiarek ◽  
...  
Keyword(s):  
Pilot Study ◽  
Attenuation Coefficient ◽  
Ultrasonic Attenuation

Measurement of ultrasonic attenuation coefficient in polymer gel dosimeters

2003 ◽  
Vol 48 (20) ◽  
pp. N269-N275 ◽  
Author(s):  
Melissa L Mather ◽  
Paul H Charles ◽  
Clive Baldock
Keyword(s):  
Attenuation Coefficient ◽  
Ultrasonic Attenuation ◽  
Polymer Gel
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