• Title/Summary/Keyword: nonlinear ultrasonic method

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Application of Nonlinear Ultrasonic Method for Monitoring of Stress State in Concrete

  • Kim, Gyu Jin;Park, Sun Jong;Kwak, Hyo Gyoung
    • Journal of the Korean Society for Nondestructive Testing
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    • v.36 no.2
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    • pp.121-129
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    • 2016
  • As the lifespan of concrete structures increases, their load carrying capacity decreases owing to cyclic loads and long-term effects such as creep and shrinkage. For these reasons, there is a necessity for stress state monitoring of concrete members. Particularly, it is necessary to evaluate the concrete structures for behavioral changes by using a technique that can overcome the measuring limitations of usual ultrasonic nondestructive evaluation methods. This paper proposes the use of a nonlinear ultrasonic method, namely, nonlinear resonant ultrasonic spectroscopy (NRUS) for the measurement of nonlinearity parameters for stress monitoring. An experiment compared the use of NRUS method and a linear ultrasonic method, namely, ultrasonic pulse velocity (UPV) to study the effects of continuously increasing loads and cyclic loads on the nonlinearity parameter. Both NRUS and UPV methods found a similar direct relationship between load level and that parameter. The NRUS method showed a higher sensitivity to micro-structural changes of concrete than UPV method. Thus, the experiment confirms the possibility of using the nonlinear ultrasonic method for stress state monitoring of concrete members.

Crack localization by laser-induced narrowband ultrasound and nonlinear ultrasonic modulation

  • Liu, Peipei;Jang, Jinho;Sohn, Hoon
    • Smart Structures and Systems
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    • v.25 no.3
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    • pp.301-310
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    • 2020
  • The laser ultrasonic technique is gaining popularity for nondestructive evaluation (NDE) applications because it is a noncontact and couplant-free method and can inspect a target from a remote distance. For the conventional laser ultrasonic techniques, a pulsed laser is often used to generate broadband ultrasonic waves in a target structure. However, for crack detection using nonlinear ultrasonic modulation, it is necessary to generate narrowband ultrasonic waves. In this study, a pulsed laser is shaped into dual-line arrays using a spatial mask and used to simultaneously excite narrowband ultrasonic waves in the target structure at two distinct frequencies. Nonlinear ultrasonic modulation will occur between the two input frequencies when they encounter a fatigue crack existing in the target structure. Then, a nonlinear damage index (DI) is defined as a function of the magnitude of the modulation components and computed over the target structure by taking advantage of laser scanning. Finally, the fatigue crack is detected and localized by visualizing the nonlinear DI over the target structure. Numerical simulations and experimental tests are performed to examine the possibility of generating narrowband ultrasonic waves using the spatial mask. The performance of the proposed fatigue crack localization technique is validated by conducting an experiment with aluminum plates containing real fatigue cracks.

Applicability of nonlinear ultrasonic technique to evaluation of thermally aged CF8M cast stainless steel

  • Kim, Jongbeom;Kim, Jin-Gyum;Kong, Byeongseo;Kim, Kyung-Mo;Jang, Changheui;Kang, Sung-Sik;Jhang, Kyung-Young
    • Nuclear Engineering and Technology
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    • v.52 no.3
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    • pp.621-625
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    • 2020
  • Cast austenitic stainless steel (CASS) is used for fabricating different components of the primary reactor coolant system of pressurized water reactors. However, the thermal embrittlement of CASS resulting from long-term operation causes structural safety problems. Ultrasonic testing for flaw detection has been used to assess the thermal embrittlement of CASS; however, the high scattering and attenuation of the ultrasonic wave propagating through CASS make it difficult to accurately quantify the flaw size. In this paper, we present a different approach for evaluating the thermal embrittlement of CASS by assessing changes in the material properties of CASS using a nonlinear ultrasonic technique, which is a potential nondestructive method. For the evaluation, we prepared CF8M specimens that were thermally aged under four different heating conditions. Nonlinear ultrasonic measurements were performed using a contact piezoelectric method to obtain the relative ultrasonic nonlinearity parameter, and a mini-sized tensile test was performed to investigate the correlation of the parameter with material properties. Experimental results showed that the ultrasonic nonlinearity parameter had a correlation with tensile properties such as the tensile strength and elongation. Consequently, we could confirm the applicability of the nonlinear ultrasonic technique to the evaluation of the thermal embrittlement of CASS.

Measurement of Ultrasonic Nonlinear Parameter by Using Non-Contact Ultrasonic Receiver (비접촉식 초음파 수신기를 이용한 초음파 비선형성 측정)

  • Kim, Jongbeom;Jhang, Kyoung-Young
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.38 no.10
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    • pp.1133-1137
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    • 2014
  • The ultrasonic nonlinear parameter ${\beta}$ is generally known as an effective parameter for evaluating material degradation. Thus far, most research has been conducted using a contact method. However, since measurement by this contact method is affected by the contact conditions between the transducer and the specimen, additional devices are required to maintain the contact conditions stable during the measurement. To avoid this inconvenience, this paper proposes a noncontact method. In this study, only the receiver was replaced with a noncontact receiver, and then, the ultrasonic nonlinear parameters measured by the newly developed noncontact receiver were compared with those measured by the contact receiver. Results obtained using both these receivers for heat-treated aluminum alloy specimens showed good agreement. From this result, we can confirm that the ultrasonic nonlinear parameter ${\beta}$ can be measured using the proposed noncontact ultrasonic method.

Development of Pressure Control System of Contact Transducer for Measurement of Ultrasonic Nonlinear Parameter

  • Lee, In-Ho;Son, Dae-Soo;Choi, Ik-Hwang;Lee, Tae-Hun;Jhang, Kyung-Young
    • Journal of the Korean Society for Nondestructive Testing
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    • v.27 no.6
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    • pp.576-581
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    • 2007
  • Ultrasonic nonlinearity has been considered as a promising method to evaluate the micro damage of material; however, its magnitude is so small that its measurement is not easy. Especially, when we use contact PZT transducer, if the contacting pressure is not kept in constant during the measurement then there exists extraneous fluctuation in the measured nonlinearity caused by the unstable contact condition, In this paper, we developed a pneumatic control system to keep the contacting pressure of transducer in constant during the measurement and analyzed the effect of contacting pressure to the ultrasonic nonlinearity measurement As a result, we found that the pressure of transducer in our measurement system should be greater than 170 kPa to measure the ultrasonic nonlinear parameter in stable with no dependency on the contacting pressure.

A Basic Research on Estimation of Material Condition by Using Stress Dependency of Sound Speed (음속의 응력의존성을 이용한 재료 상태평가에 대한 기초적 연구)

  • Kim, K.J.;Jhang, K.Y.
    • Journal of the Korean Society for Precision Engineering
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    • v.13 no.4
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    • pp.53-60
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    • 1996
  • In the conventional linear elasticity, sound speed is determined by only elastic modulus and density of the medium. In actual, however, sound speed depends on the stress and this dependency becomes nonlinear as the stress increases. These phenomena can be introducing nonlinear elastic modulus. In this paper, relationships between nonlinear elastic modulus up to 4th order and the internal status of materials are discussed through computer simulations and experiments. For the measurement of sound speed, a new type of measurement system using ultrasonic wave is proposed on the basis of ultrasonic pulse echo method which has been generally used in nondestructive ultrasonic test equipment. In order to confirm the stress dependency of sound speed, several experiments are carried out for alumina specimen.

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Correlation between Ultrasonic Nonlinearity and Elastic Nonlinearity in Heat-Treated Aluminum Alloy

  • Kim, Jongbeom;Jhang, Kyung-Young
    • Journal of the Korean Society for Nondestructive Testing
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    • v.37 no.2
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    • pp.115-121
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    • 2017
  • The nonlinear ultrasonic technique is a potential nondestructive method to evaluate material degradation, in which the ultrasonic nonlinearity parameter is usually measured. The ultrasonic nonlinearity parameter is defined by the elastic nonlinearity coefficients of the nonlinear Hooke's equation. Therefore, even though the ultrasonic nonlinearity parameter is not equal to the elastic nonlinearity parameter, they have a close relationship. However, there has been no experimental verification of the relationship between the ultrasonic and elastic nonlinearity parameters. In this study, the relationship is experimentally verified for a heat-treated aluminum alloy. Specimens of the aluminum alloy were heat-treated at $300^{\circ}C$ for different periods of time (0, 1, 2, 5, 10, 20, and 50 h). The relative ultrasonic nonlinearity parameter of each specimen was then measured, and the elastic nonlinearity parameter was determined by fitting the stress-strain curve obtained from a tensile test to the 5th-order-polynomial nonlinear Hooke's equation. The results showed that the variations in these parameters were in good agreement with each other.

Non-destructive assessment of carbonation in concrete using the ultrasonic test: Influenced parameters

  • Javad Royaei;Fatemeh Nouban;Kabir Sadeghi
    • Structural Engineering and Mechanics
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    • v.89 no.3
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    • pp.301-308
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    • 2024
  • Concrete carbonation is a continuous and slow process from the outside to the inside, in which its penetration slows down with the increased depth of carbonation. In this paper, the results of the evaluation of the measurement of concrete carbonation depth using a non-destructive ultrasonic testing method are presented. According to the results, the relative nonlinear parameter caused more sensitivity in carbonation changes compared to Rayleigh's fuzzy velocity. Thus, the acoustic nonlinear parameter is expected to be applied as a quantitative index to recognize carbonation effects. In this research, combo diagrams were developed based on the results of ultrasonic testing and the experiment to determine carbonation depth using a phenolphthalein solution, which could be considered as instructions in the projects involving non-destructive ultrasonic test methods. The minimum and maximum accuracy of this method were 89% and 97%, respectively, which is a reasonable range for operational projects. From the analysis performed, some useful expressions are found by applying the regression analysis for the nonlinearity index and the carbonation penetration depth values as a guideline.

The Evaluation of Partially Degraded Material Using Nonlinear Propagation Characteristics of Ultrasonic Wave (초음파 비선형 전파특성을 이용한 부분 열화 재료의 평가)

  • Kim, Kyung-Cho;Jhang, Kyung-Young;Hisashi, Yamawaki
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.2
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    • pp.214-219
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    • 2001
  • In this paper, the nonlinear behavior of ultrasonic wave in partially degraded material is considered. For this aim, FDM(finite difference method) model for the nonlinear wave equation was developed with the restriction to the 1-D longitudinal wave motion and how the partial degradation in material contributes to the detected nonlinear parameter was analyzed quantitatively. In order to verify the rightness of this simulation method, the relation between the detected nonlinear parameter and the continuous distribution of degradation obtained from simulation was compared with experiment results and the simulation and experiment results showed similar tendency. It can be known from simulation result that the degree of degradation, the range of degradation and the continuous distribution of degradation have strong correlation with the detected nonlinear parameter. As it was possible in these simulations that only special part is assumed as degraded one, the quantitative evaluation of partially degraded material may be obtained by using this method.

Measurement of Nonlinear Elastic Constants and Material Characterization by Using Nonlinear Elasto-acoustics (비선형 탄성-음향 효과를 이용한 비선형 탄성 계수의 계측과 금속재료의 특성평가)

  • ;;Sato, Takuso
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.8
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    • pp.1971-1979
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    • 1993
  • In this paper, a new method to estimate stress status in metal nondestructively by using nonlinear dependency of sound speed on stress is proposed. For the purpose, equivalent nonlinear elastic constants up to fourth-order are introduced and a new characteristic parameter given as a function of these constants is presented. And a concrete system to measure the characteristic parameter is constructed by electromagnetic pumping wave and ultrasonic probing wave system. Some experimental results for Al alloy showed that the estimation of stress status in metal is possible by the proposed method.