• Title, Summary, Keyword: Ultrasonic velocity

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Effect of Acetylation on Ultrasonic Velocity of Bamboo (아세틸화 처리가 대나무재의 초음파 전달 속도에 미치는 영향)

  • Kang, Ho-Yang;Lee, Gwan-Young
    • Journal of the Korean Wood Science and Technology
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    • v.25 no.3
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    • pp.8-15
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    • 1997
  • The ultrasonic velocity and dynamic MOE of acetylated bamboos were investigated using PUNDIT, a transit time measuring device for longitudinal ultrasonic propagation. Bamboo specimens were boiled in acetic anhydride for 2, 4 and 6 hours, and the maximum average WPG (Weight Percentage Gain) of 19% was obtained at 6 hours. The volumes of acetylated bamboos increase with boiling time and WPG, while as WPG increases their oven-dry densities generally increase with a concave around 5% WPG. This oven-dry density pattern likely influences the trends of ultrasonic velocity and dynamic MOE. which generally decrease with a convex around 5% WPG. It is postulated that during boiling extractives in a bamboo move and aggregate at its surfaces transiently, resulting in the increase of ultrasonic velocity and dynamic MOE. To explain the fact that ultrasonic velocity varies with WPG a simple model was proposed and some ultrasonic properties of a transmitted wave were examined.

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The Effect of Graphite Morphology on the Propagation of Ultrasonic Wave in Ductile Cast Iron (구상흑연주철에서 초음파 전파속도에 미치는 흑연형상의 영향)

  • Lee, Kye-Wan;Yang, No-Seok;Park, Un-Su
    • Journal of Korea Foundry Society
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    • v.9 no.3
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    • pp.228-236
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    • 1989
  • The relationships between nodularity, tensile property and ultrasonic velocity were studied in ductile iron castings having similar matrix structure. Also, the effects of heat treatment and the number of graphite nodules on the ultrasonic velocity were investigated. The results were as follows 1. The ultrasonic velocity increased proportionally with increassing nodularity and tensile strength. 2. The ultrasonic velocity in annealed and normalized state decreased average 1.7% and 3.4% respectively than that in as cast state. 3. The ultrasonic velocity increased with increasing the number of graphite nodules. Therefore, ductile iron castings can be evaluated in the only case of castings having the same manufacturing history by ultrasonic velocity.

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The Effect of Tempering Temperature on Ultrasonic Velocity Property at the Quenched SCM 440 Steel (퀜칭한 SCM 440 강에서 초음파 전파특성에 미치는 템퍼링온도의 영향)

  • Lee, K.W.;Kim, M.I.;Park, U.S.
    • Journal of the Korean Society for Heat Treatment
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    • v.4 no.3
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    • pp.54-62
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    • 1991
  • The effect of tempering temperature on the ultrasonic propagation velocity at SCM 440 steel quenched from $870^{\circ}C$ and $1000^{\circ}C$ has been studied by metallurgical and crystallographical observation. The measurements of ultrasonic velocity were made on the specimen by appling an immersion ultrasonic pulse-echo technique with a constant frequency of 10 MHz. The quenched microstructure of this steel was a lath martensite. As the tempering temperature was increased, the martensite was transformed into the tempered martensite composed of cementite and carbide. The ultrasonic velocity increased with increasing the tempering temperature. It was thought that these were resulted from the microstructural transformation. The change of ultrasonic propagation velocity with quenching and tempering heat treatment was resulted from microstrain due to the change of internal stress. Considering these results concerning to the change of ultrasonic propagation velocity. the phenomena of microstructural transformation were estimated. Consequently, it was thought that the degree of quenching and tempered heat treatment of steel could be nondestructively evaluated with the change of ultrasonic propagation velocity.

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Estimating Compressive Strength of High Strength Concrerte by Ultrasonic Pulse Velocity Method (초음파속도법에 의한 고강도 콘크리트의 압축강도 추정에 관한 연구)

  • Lim, Seo-Hyung;Kang, Hyun-Sik
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.5 no.3
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    • pp.123-130
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    • 2001
  • The purpose of this study is to suggest the non-destructive equation for the estimation of concrete strength by ultrasonic pulse velocity at the Age of 28day compressive strength of $600{\sim}1000kg/cm^2$. For this purpose, selected test variables were water-hinder ratio, replacement ratio of silica fume, binder content, maximum size of coarse aggregate and sand-aggregate ratio. From the results, the average increase or decrease of ultrasonic pulse velocity is 61m/sec for each 1% of moisture content. And the correlation equation between the ultrasonic pulse velocity and the compressive strength of concrete is as follows. $F_c=896.3V_p-3514$ ($R^2$ = 0.81) where, $F_c$ : compressive strength($kgf/cm^2$), $V_p$ : ultrasonic velocity(km/sec).

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Temperature Effect on Ultrasonic Stress Wave Velocity of Wood (목재 초음파 전달속도에 대한 온도의 영향)

  • Kang, Ho-Yang
    • Journal of the Korean Wood Science and Technology
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    • v.27 no.1
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    • pp.50-55
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    • 1999
  • Since ultrasonic stress wave velocity varies with wood temperature and moisture content, ultrasonic stress wave could be a tool to predict wood moisture content if temperature effect could be eliminated. This temperature effect was investigated by measuring the velocities of ultrasonic stress waves transmitting through air, a metal bar and a dimension lumber at various temperatures. For air the velocity and amplitude of the ultrasonic stress wave increase with temperature, while for a metal bar and a dimension lumber those decrease as temperature increases. However all three materials showed velocity hystereses with a temperature cycle. The effect of temperature and moisture content on stress wave velocity of a dimension lumber was depicted in the form of a three dimensional graph. The plot of stress wave velocity vs. wood moisture content was well fitted by two regression equations: a exponential equation below 46% and a linear equation above 46%.

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The Change of Ultrasonic Transmission Velocity by Wood Decay

  • Hwang, Won-Joung;Lee, Hyun-Mi;Park, Young-Ran;Lee, Dong-Heub
    • Journal of the Korean Wood Science and Technology
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    • v.42 no.2
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    • pp.214-221
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    • 2014
  • The deterioration in wood by the brown-rot fungus (Fomitopsispalustris) and the white-rot fungus (Trametesversicolor) were measured using ultrasonic velocity. Those were used for the decay exposure and 4 wood species of wood as the test specimens, Pinusdensiflora, Larixkaempferi, Pinuskoraiensis and Pinusrigida, were chosen with both the brown- and white-rot culture petridish during 12 weeks. After 12 weeks, the decrease rate of ultrasonic velocity was measured at 10~15%. In both brown- and white-rot exposure experiments, P. rigida showed significant decrease in ultrasonic velocity (20%), L. kaempferi on the other hand did not show decrease in ultrasonic velocity. After the fungal exposure experiment, the inside of specimens was investigated by computer tomography (C/T). After C/T investigation, bending tests were performed.

Quantitative Analysis for Termites Damage of Wooden Heritage using Ultrasonic Pulse Velocity (초음파 전파속도법을 이용한 목조 문화유산 흰개미 피해의 정량 평가)

  • Ahn, Jae-Cheol
    • Journal of architectural history
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    • v.24 no.5
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    • pp.41-48
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    • 2015
  • Quantitative analysis of termites damage is important in terms of conservation and maintenance of wooden cultural heritage buildings, because termites makes cavities and decreases the section area of wooden structural members. The purpose of this study is to forecast the range and spread of termites damage in the wooden structural members by using ultrasonic pulse velocity method. Ultrasonic pulse velocity has been used as one of non-destructive test to analysis the internal defect by using difference velocity between medium material and cavity. This method would be effective to analysis termites damages. From the result of the ultrasonic velocity test, the loss rate of area effected by termites damage had a strong correlation with ultrasonic velocity. And it is possible to predict the loss rate of area from by termites damage by using regression equation in the case of structural member of fine tree.

Ultrasonic Velocity and Absorption Measurements for Polyacrylamide and Water Solutions

  • Bae, Jong-Rim;Kim, Jeong-Koo;Yi, Meyung-Ha
    • The Journal of the Acoustical Society of Korea
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    • v.22 no.4E
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    • pp.155-160
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    • 2003
  • Both ultrasonic velocity at 3 MHz and absorption coefficient for the frequency range of 0.2-2 MHz were measured in an aqueous solution of polyacrylamide for the concentration range of 0.5% to 2.5% by weight. Pulse echo overlap method was taken for measuring the ultrasonic velocity over the temperature range of 10-90℃ and the high-Q ultrasonic resonator method was used for the absorption coefficient at 30℃. The velocity exhibited a maximum value at approximately 70℃, 71℃, 72℃, 73℃ and 74℃ in 2.5%, 2.0%, 1.5%, 1.0%, and 0.5% solutions, respectively. The velocity increased with the concentration at a given temperature. The ultrasonic absorption (a/f²) at a given temperature increased linearly with the concentration for the concentration below 1.5%, but suddenly increased for the concentration above 1.5% concentration. The value of a/f² at 1MHz was entirely due to the classical Stoke's viscous effect. The ultrasonic relaxation in polyacrylamide aqueous solutions, which may be the result of structural fluctuations of polymer molecules such as the segmental motion of the polymer chains, was observed, and at 2.5%, the value of a/f² was found to suddenly increase as frequency decreased.

Simultaneous Measurement of Ultrasonic Velocity and Thickness of Isotropic and Homogeneous Solids Using Two Transducers (두개의 탐촉자를 사용한 등방성 균일 고체의 초음파 속도 및 두께 동시 측정법)

  • Lee, Jeong-Ki;Kwon, Jin-O;Kim, Young-H.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.19 no.5
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    • pp.363-368
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    • 1999
  • Ultrasonic pulse-echo methods measuring the transit time through specimens have been widely used in determination of ultrasonic velocity and thickness of specimens. Usually, to determine the velocity of the ultrasonic. the transit time of the ultrasonic pulse through specimen is measured by using the ultrasonic measuring equipment such as the oscilloscope including ultrasonic pulser/receiver and the thickness of the specimen is measured by using the length measuring instrument such as micrometer or vernier calipers etc., i. e. each parameter is measured by using each measuring method. In the case of the measuring the thickness of a specimen by using the ultrasonics. the ultrasonic equipments, which measure the thickness, such as the ultrasonic thickness gauge must be calibrated by using the reference block of which the ultrasonic velocity is known beforehand. In the present work, we proposed a new method for simultaneous measurement of ultrasonic velocity and thickness without reference blocks. Experimental results for several specimens show that proposed method have good agreements with those by traditional ultrasonic method.

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A Study on Ultrasonic Technique for Measuring Gas Temperature (기체온도 측정을 위한 초음파 계측에 관한 연구)

  • Yoon, Cheon Han;Choi, Young;Jeon, Heung Shin
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.23 no.7
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    • pp.893-900
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    • 1999
  • Measuring temperature with ultrasonic wave apparatus is desirable in the cue of gas below $300^{\circ}$ because of the fact that the temperature of gas is the function of only sound velocity. In this study, being used a heatable wind channel and a blower. the variation of temperature is observed in accordance with flow rate(air velocity). The frequency modulation method is used to measure the temperature which is varying in hot air flow up to $100^{\circ}$. The length changed in the position of ultrasonic sensors is considered. Also. the effects of air velocity at the same temperature and various facing angles of ultrasonic sensors are considered. As a result of this study. it has been found that the temperature in gas flow is correctly measured regardless of both the distance of ultrasonic sensors and the variation of air velocity. and that there is just a little influence of facing angles.