• The Journal of the Acoustical Society of Korea
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• 제22권4E호
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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.

• 비파괴검사학회지
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• 제19권5호
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• pp.363-368
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• 1999

시험체의 두께나 초음파 속도를 측정하기 위해서 초음파 펄스-에코법이 널리 사용되고 있다. 초음파 속도를 결정하기 위해서는 초음파 송수신 장치를 포함한 오실로스코우프와 같은 초음파 측정 장치를 사용하여 시험편에서의 초음파진행 시간을 측정하고, 초음파 진행 거리에 해당하는 시험편의 두께를 버어니어 캘리퍼스 또는 마이크로미터와 같은 길이측정 도구를 사용하여 측정한다. 그리고 초음파를 이용하여 시험편의 두께를 측정할 때에는 초음파 속도를 알고 있는 대비 시험편으로 기준을 설정하여야 한다. 본 연구에서는, 대비 시험편 없이 재료의 두께와 초음파 속도를 동시에 구하는 방법을 제시하였다. 재질과 두께를 달리한 여러 시험편에서 측정된 초음파 속도와 두께가 기존의 방법에 의해 측정한 값과 잘 일치하였다.

• 대한기계학회논문집B
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• 제23권7호
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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.

• The Journal of the Acoustical Society of Korea
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• 제23권4E호
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• pp.140-145
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• 2004

A laboratory study was carried out to investigate the change of ultrasonic velocity as a function of temperature for fluid mud (i.e., suspension). Pulse transmission technique with ultrasonic wave was used for ultrasonic velocity measurement. The five samples for fluid mud were prepared for concentration range of $30.6{\%}\;(1.24\;g/cm^{3}\;in\;density),\;23.3{\%}\;(1.19\;g/cm^{3}),\;11.5{\%}(1.10\;g/cm^{3}),\;7.8{\%}\;(1.08\;g/cm^{3}),\;and\;3.8{\%}\;(1.05\;g/cm^{3})$ by weight. The ultrasonic velocity in fluid mud was investigated to increase $(approximately\;2.83\;to\;4.95\;m/s/^{\circ}C)$ with increasing temperature, due to the effect of viscosity and compressibility of water with changing temperature. But the increasing rate tends to decrease at temperature higher than $30^{\circ}C,$ caused by the effect of viscosity. The concentration of fluid mud more affect to the ultrasonic velocity at higher temperature range than that at lower temperature. Overall the temperature effect on the ultrasonic velocity in fluid mud was a similar rate as for distilled water and seawater, suggesting fluid mud significantly depends on the behavior of water.

• Nuclear Engineering and Technology
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• 제35권5호
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• pp.369-377
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• 2003

Since Zr-2.5Nb pressure tubes have a high risk for the formation of blisters during their operation in pressurized heavy water reactors, there has been a strong incentive to develop a method for the non-destructive detection of blisters grown on the tube surfaces. However, because there is little mismatch in acoustic impedance between the hydride blisters and zirconium matrix, it is not easy to distinguish the boundary between the blister and zirconium matrix with conventional ultrasonic methods. This study has focused on the development of a special ultrasonic method, so called ultrasonic velocity ratio method for a reliable detection of blisters formed on Zr-2.5Nb pressure tubes. Hydride blisters were grown on the outer surface of the Zr-2.5Nb pressure tube using a cold finger attached to a steady state thermal diffusion equipment. To maximize a difference in the ultrasonic velocity in hydride blisters and the zirconium matrix, the ultrasonic velocity ratio of longitudinal wave to shear wave, $V_L/V_S$, has been determined based on the flight time of the longitudinal echo and reflected shear echo from the outer surface of the tubes. The feasibility of the ultrasonic velocity ratio method is confirmed by comparing the contour plots reproduced by this method with those of the blisters grown on the Zr-2.5Nb pressure tubes.

• 한국소음진동공학회논문집
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• 제20권11호
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• pp.1078-1088
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• 2010

In order to analyze the quantitative characteristics of acoustic streaming, experimental setup of 3-D stereoscopic PIV(particle imaging velocimetry) was designed and quantitative ultrasonic flow fields in the gap between the ultrasonic vibrator and heat source were measured. Utilizing acoustic streaming induced by ultrasonic vibration, surface temperature drop of cooling object was also measured. The study on smart cooling method by acoustic streaming induced by ultrasonic vibration was performed due to the empirical relations of flow pattern, average flow velocity, different gaps, and enhancement on cooling rates in the gap. Average velocity fields and maximum acoustic streaming velocity in the open gap between the stationary cylindrical heat source and ultrasonic vibrator were experimentally measured at no vibration, resonance, and non-resonance. It was clearly observed that the enhancement of cooling rates existed owing to the acoustic air flow in the gap at resonance and non-resonance induced by ultrasonic vibration. The ultrasonic wave propagating into air in the gap creates steady-state secondary eddy called acoustic streaming which enhances heat transfer from the heat source to encompassing air. The intensity of the acoustic streaming induced by ultrasonic vibration experimentally depended upon the gap between the heat source and ultrasonic vibrator. The ultrasonic vibration at resonance caused the increase of the acoustic streaming velocity and convective heat transfer augmentation when the flow fields by 3D stereoscopic PIV and temperature drop of the heat source were measured experimentally. The acoustic streaming velocity of air enhancement on cooling rates in the gap is maximal when the gap agrees with the multiples of half wavelength of the ultrasonic wave, which is specifically 12 mm.

• 한국농공학회지
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• 제35권4호
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• pp.38-46
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• 1993

This study is to analyze effect of exposure environment and mode of ASR on the engineering properties of synthetic lightweight aggregate concrete, such as dynamic modulus of elasticity and ultrasonic pulse velocity. The results of this study are summarized as foflows ; 1. The expansion rate of each exposure environment in 380$^{\circ}$C and NaCI 4% solution was shown higher than in 20$^{\circ}$C and normal water. The expansion rate of each exposure mode was largely shown in order of fjill immersion, wetting/drying, half immersion. 2. The dynamic modulus of elasticty and ultrasonic pulse velocity of each exposure environment in 38$^{\circ}$C and NaCl 4% solution was shown less than in 20$^{\circ}$C and normal water. The dynamic modulus of elasticity and ultrasonic pulse velocity of each exposure mode was shown smaller in order of full immersion, wetting/drying, half imersion.3. The relation between dynamic modulus of elasticity and ultrasonic pulse velocity was highly significant. The dynamic modulus of elasticity was increased with increase of ultrasonic pulse velocity. The decreasing rate of the dynamic modulus of elasticity was shown 2.1~3.4 times higher than the ultrasonic pulse velocity at each age, exposure environment and mode, respectively. 4. The expansion of each exposure environment and mode was increased with increase of curing age. The dynamic modulus of elasticity and ultrasonic pulse velocity of those concrete was increased with increase of curing age. At the curing age 28 days, the highest properties was showed at each type concrete, it was gradually decreased with increase of curing age. Specially, at the curing age 98 days of full immersion, the rate of expansion of type D was shown 3.95 times higher than the type A. But the dynamic modulus of elasticity and ultrasonic pulse velocity was decreased 17% and 8.3%.

• Journal of the Korean Wood Science and Technology
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• 제43권4호
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• pp.486-493
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• 2015

설치된 데크재에 대한 성능을 평가하기 위하여 초음파 비파괴시험법을 사용하였다. 먼저 3종류의 데크재에 대해 트랜스듀서의 배치에 따른 직접법과 간접법간의 측정방법간의 차이를 검증하였으며 두 번째로 설치된 데크재의 사용시간의 경과에 따른 초음파속도를 측정 비교하였다. 마지막으로 데크재의 사용수명을 파악하기 위하여 사용시간의 경과에 따른 초음파속도의 변화를 조사하였다. 시험결과 직접법과 간접법간의 측정방법간의 차이는 없는 것으로 나타났으며 직접법에 대한 간접법의 비율은 1.02와 1.05로 각각 나타났다. 설치된 데크재에서 시간의 경과에 따라 초음파 속도는 감소하였으며 이들 간의 관계는 선형으로 나타났다. 시험결과로부터 초음파 비파괴시험법은 설치된 데크재의 유지보수에 관한 효율적인 수단이 될 수 있을 것으로 생각된다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.619-622
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• 2005

This study concerns the new strength equation of concrete by ultrasonic pulse velocity test. There are not only few estimate strength equations of concrete by ultrasonic pulse velocity test, but also many problems to apply them because of time,. cost, easiness, structural damage, reliability and so on. For this study, there performed a series of test and proposed equations as follows; Linear: ${\Large f}_{ck}=-193.15+60.97Vp\;r^2=77.9\%$ Quadratic : ${\Large f}_{ck}=276.85-189.64Vp+33.22Vp^2\;r^2=80.3\%$ here, $f_{ck}$ : Estimated compressive strength of concrete by MPa Vp : Ultrasonic Pulse Velocity of concrete by km/sec

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2017년도 춘계 학술논문 발표대회
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• pp.48-49
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• 2017

In order to examine the effect of voids on the ultrasonic wave velocity, specimens made of Silica-Sand with voids were prepared for the measurements. The volume fraction of 0, 15, and 30% of voids were used to compare the differences. Because of its more homogeneous distribution of materials properties, the Silica-Sand specimens were used, as compared to mortar specimens. The results showed clear change in ultrasonic wave velocity with different volume fraction of voids. This result is to be used for the estimation of the integrity of concrete structures using ultrasonic wave velocity method as nondestructive testing.