• Title/Summary/Keyword: Ultrasonic nondestructive testing

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Evaluation of the Surface Crack by a Large Aperture Ultrasonic Probe (대구경 초음파 탐촉자를 이용한 표면균열 평가)

  • Cho, Yong-Sang;Kim, Jae-Hoon
    • Journal of the Korean Society for Nondestructive Testing
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    • v.24 no.2
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    • pp.180-185
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    • 2004
  • Conventional ultrasonic examination to detect micro and small surface cracks is based on the pulse-echo technique using a normal immersion focused transducer with high frequency, or an angle-beam transducer generating surface waves. It is difficult to make an automatic ultrasonic system that can detect micro and small surface cracks and position in a large structure like steel and ceramic rolls, because of the huge data of inspection and the ambiguous position data of the transducer. In this study, a high-precision scanning acoustic microscope with a 10MHz large-aperture transducer has been used to assess the existence, position and depth of a surface crack from the real-time A, B, C scans obtained by exploiting the ultrasonic diffraction. The ultrasonic method with large aperture transducer has improved the accuracy of the crack depth assessment and also the scanning speed by ten times, compared with the conventional ultrasonic methods.

Non-Contact Ultrasonic Testing of Aircraft Joints using Laser Generated Lamb Wave (레이저 여기 램파를 이용한 항공기 판재 접합부의 비접촉식 초음파 검사)

  • Jhang, Kyoung-Young;Kim, Hong-Joon;Ceringlia, Donatella;Djordjevic, Boro
    • Journal of the Korean Society for Nondestructive Testing
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    • v.21 no.2
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    • pp.163-168
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    • 2001
  • Due to aging, adhesively bonded and riveted aircraft lap joints can contain distends, cracks around rivet holes, fatigue induced flaws, and corrosion. It is required for the safety of aircraft to inspect these defects through the whole region of mint in rapid speed. Bond quality or adhesively bonded and riveted aluminum lap splice joints is investigated using non-contact remote ultrasonic nondestructive evaluation (NDE). Non-contact ultrasonic tests are performed using laser generation and air-coupled transducer detection. A Q-switched Nd:YAG laser and a periodic transmission mask are used to generate a selected Lamb mode. The Lamb wave is generated on one side of the lap splice joint, propagates along the plate, interacts with the joint and is detected on the other side by a micromachined air-coupled capacitance transducer. Analysis of recorded signals allows to evaluate the condition of the bond.

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Model of Reliability Assessment in Ultrasonic Nondestructive Inspection (초음파 비파괴검사의 신뢰도 평가 모델)

  • Park, Ik-Keun;Park, Un-Su;Kim, Hyun-Mook;Park, Yoon-Won;Kang, Suk-Chull;Choi, Young-Hwan;Lee, Jin-Ho
    • Proceedings of the KSME Conference
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    • 2001.11a
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    • pp.240-245
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    • 2001
  • Ultrasonic inspection system is consisted of the operator, equipment and procedure. The reliability of results in ultrasonic inspection is affected by its ability. Furthermore, the reliability of nondestructive testing is influenced by the inspection environment, other materials and types of defect. Therefore, it is very difficult to estimate the reliability of NDT due to various factors. In this study, the probability of detection, used logistic probability model and Monte Carlo simulation, estimated the reliability of ultrasonic inspection. The utility of the NDT reliability assesment is verified by the analysis of the data from round robin test applied these models.

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Measurement of Ultrasonic Wave Velocity Changes in Silica-Sand Specimens with Voids (공극을 포함한 실리카샌드 시편의 초음파 속도변화 측정)

  • Kim, Dae-You;Rhim, Hong-Chul;Cho, Youn-Jin
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2017.05a
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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.

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Study on Highly Accuracy Quality Evaluation of Spot Weld by use of Image Processing Technique

    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.5 no.4
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    • pp.38-46
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    • 1996
  • This paper discusses the feasibility of Ultrasonic Nondestructive Evaluation (UNDE) technique for sport weld quality. Ultrasonic c-scan image assisted by image processing technique was used for Nondestructive Evaluation(NDE) of spot weld quality. Ultrasonic testing results obtained were confirmed and compared by Optical Microscope and SAM(Scanning Acoustic Mircroscope) observation of the spot-weld cross section, The results show that the nugget dinameter can be successfully measured with the accuracy of 0.5mm. It was ascertained that ultrasonic c-scan technique is very effective method for the sake of the approach to the quantitative measurement of nugget diameter and the discrimination of the corona bond from nugget. Additional support for the above conclusions is provided by the results for galvanized steel. The ultrasonic results for galvanized welds generally correspond to the results for uncoated steel. Finally, it was found that the above-mentioned technique can be sufficiently applied to NDE method for securing the Quality Assurance(QA) of spot welded products in production line.

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On the Beam Focusing Behavior of Time Reversed Ultrasonic Arrays Using a Multi-Gaussian Beam Model

  • Jeong, Hyun-Jo;Lee, Jeong-Sik;Jeong, Yon-Ho;Bae, Sung-Min
    • Journal of the Korean Society for Nondestructive Testing
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    • v.28 no.6
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    • pp.531-537
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    • 2008
  • One of the fundamental features of time reversal acoustic (TRA) techniques is the ability to focus the propagating ultrasonic beam to a specific point within the test material. Therefore, it is important to understand the focusing properties of a TR device in many applications including nondestructive testing. In this paper, we employ an analytical scheme for the analysis of TR beam focusing in a homogeneous medium. More specifically, a nonparaxial multi-Gaussian beam (NMGB) model is used to simulate the focusing behavior of array transducers composed of multiple rectangular elements. The NMGB model is found to generate accurate beam fields beyond the nonparaxial region. Two different simulation cases are considered here for the focal points specified on and off from the central axis of the array transducer. The simulation results show that the focal spot size increases with increasing focal length and focal angle. Furthermore, the maximum velocity amplitude does not always coincide with the specified focal point. Simulation results for the off-axis focusing cases do demonstrate the accurate steering capability of the TR focusing.

Study on the Measurement of Safety of a High Pressure Vessel (고압용기(高壓容器)의 안전도(安全度) 측정(測定)에 관(關)한 연구(硏究))

  • Yim, Tong-Kyu;Choi, Man-Yong;Han, Eung-Kyo
    • Journal of the Korean Society for Nondestructive Testing
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    • v.2 no.2
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    • pp.9-16
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    • 1983
  • There are two weak points in a high pressure vessel, one is a corner, the other is a crack on the base. In order to evaluate safety of a department of a corner and a crack like a starfish on the base in a high pressure vessel (working pressure: $130kg/cm^{2}$), which was made by Marison's Process, we analyzed stress by strain gauge, measured thickness and hardness by ultrasonic testing, and were able to test pressure by water pressure from nondestructive testing. Also destructive testings were applied to measure thickness and to observe microstructure and chemical composition of a corner on the base. From the results of the experiment, values of experiment were satisfied with a condition of application. But, it is considered that a crack on the base is to be investigated with more by Fracture Mechanics.

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Defects Classification with UT Signals in Pressure Vessel Weld by Fuzzy Theory (퍼지이론을 이용한 압력용기 용접부 초음파 결함 특성 분류)

  • Sim, C.M.;Choi, H.L.;Baik, H.K.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.17 no.1
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    • pp.11-22
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    • 1997
  • It is very essential to get the accurate classification of defects in primary pressure vessel and piping welds for the safety of nuclear power plant. Ultrasonic testing has been widely applied to inspect primary pressure vessel and piping welds of nuclear power plants during PSI / ISI. Classification of flaws in weldments from their ultrasonic scattering signals is very important in quantitative nondestructive evaluation. This problem is ideally suited to a modern ultrasonic Pattern recognition technique. Here, a brief discussion on systematic approach to this methodology is presented including ultrasonic feature extraction, feature selection and classification. A stronger emphasis is placed on Fuzzy-UTSCS (UT signal classification system) as efficient classifiers for many practical classification problems. As an example Fuzzy-UTSCS is applied to classify flaws in ferrite pressure vessel weldments into two types such as linear and volumetric. It is shown that Fuzzy-UTSCS is able to exhibit higher performance than other classifiers in the defect classification.

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Evaluation of High Attenuation Material Using Utrasonic Wave Analysis (초음파의 파형 해석에 의한 고감쇠 재료의 평가)

  • Nam, Young-Hyun
    • Journal of the Korean Society for Nondestructive Testing
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    • v.15 no.2
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    • pp.364-370
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    • 1995
  • The purpose of this paper was to develop a nondestructive evaluation method of sintered material by ultrasonic method. The density distribution of sintered material becomes inhomogeneous partially because of the friction between the powder and the die during compaction. The inhomogeneity was investigated by measurement of the energy attenuation coefficient and the shift of the center frequency in the frequency spectrum of the ultrasonic reflection echo. The experimental results showed that the center frequency of reflection wave depended linearly on the density of sintered materials. However, the attenuation coefficient decreased inversely as the density increased. This study shows that the shift of the center frequency in the frequency spectrum of reflection wave can be used to a nondestructive evaluation of sintered materials.

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Development and Characterization of the Electromagnetic Acoustic Transducer for Tubes (튜브탐상용 EMAT 제작 및 특성조사)

  • Ahn, Bong-Young;Lee, Se-Kyung
    • Journal of the Korean Society for Nondestructive Testing
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    • v.5 no.2
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    • pp.42-48
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    • 1986
  • Electromagnetic - Acoustic Transducers for the inspection of tubes were developed using permanent magnets and induction coils. The propagation velocity of ultrasonic waves in a tude wall was measured by the transducers. The position of a flaw in a tube and the relative size of flaws with different size were measured.

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