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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Society for Nondestructive Testing
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Journal DOI :
The Korean Society for Nondestructive Testing
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Volume & Issues
Volume 29, Issue 6 - Dec 2009
Volume 29, Issue 5 - Oct 2009
Volume 29, Issue 4 - Aug 2009
Volume 29, Issue 3 - Jun 2009
Volume 29, Issue 2 - Apr 2009
Volume 29, Issue 1 - Feb 2009
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Depth Sizing of Notch Fatigue Crack Using Diffracted Ultrasonic Wave
Jin, Mei-Ling ; Lee, Tae-Hun ; Park, Byung-Jun ; Jhang, Kyung-Young ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 5, 2009, Pages 405~414
This paper proposed a methodology based on ultrasonic diffraction technique to inspect the depth of a crack initiated from a notch of CT specimen by fatigue test, and its usefulness was verified by experiments. Especially, in order to identify accurately the diffractive waves from the crack tip in the situation where there are extra diffractive elements such as a notch, we have tried imaging by transducer scan and analyzed the propagation path of diffracted wave. Two specimens with and without a crack were experimented. Higher frequency and larger refractive angle of transducer showed a tendency to decrease the error in the measurements, and the measured crack depth showed an error less than 0.38 mm in case of 4 MHz
. The proposed methodology is applicable to weak diffractive sources, and so that it would be useful to inspect micro cracks and for their depth sizing.
Evaluation of Surface Fatigue Degradation Using Acoustic Nonlinearity of Surface Wave
Lee, Jae-Ik ; Lee, Tae-Hun ; Jhang, Kyung-Young ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 5, 2009, Pages 415~420
This paper reports the results of a case study for the evaluation of surface damage by using acoustic nonlinearity of surface wave. In this study, the experimental system was constructed to measure the acoustic nonlinear parameter of surface wave in an Aluminum 6061 T6 specimen of which surface was damaged by the three point bending fatigue test, and magnitudes of nonlinear parameter measured before and after the fatigue test were compared. Especially, since the surface fatigue damage by the three point bending is concentrated at the central position of loading, the change in the nonlinear parameter around this position was monitored. Experimental results showed that the measured nonlinear parameter at the outside of this position after the fatigue test was almost same as the initial value before the fatigue test, since the fatigue damage at this position was little. However, clear increase in the nonlinear parameter was noticed after the fatigue test at the central position of specimen where the surface fatigue damage is expected to be concentrated.
A Study on Measuring the Temperature and Revising the Result When Measuring the Temperature of NPP Pipes Using Infrared Thermography
Kim, Kyeong-Suk ; Jung, Hyun-Chul ; Pack, Chan-Joo ; Kim, Dong-Soo ; Jung, Duk-Woon ; Chang, Ho-Sub ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 5, 2009, Pages 421~426
The emissivity is different because the emitted angle changes according to the position of the infrared thermography camera and object. Because of this, the temperature distribution expressed when measuring the temperature by using the infrared thermography system is not the accuracy temperature. Although the real surface temperature is constant, the temperature measured by using infrared thermography camera have error in accordance with the value of emissivity. In this paper, the temperatures of the round cylindrical object and the flat square object that heated to the equal temperature were measured by infrared thermography camera. The emissivity calibration formula and correction table are made with the affect of the view angle and emission angle form the surface temperature value. The error of measured temperature values are corrected by using the emissivity calibration formula and correction table, and apply to defect detection of the nuclear power plant pipe. From the calibration method, reliability surface temperature values were obtained.
Development of a Modular Magnetostrictive Transducer for Torsional Guided Wave Transduction in a Cylindrical Structure
Cho, Seung-Hyun ; Park, Jae-Ha ; Kwon, Hyu-Sang ; Ahn, Bong-Young ; Lee, Seung-Seok ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 5, 2009, Pages 427~435
Cylindrical structures such as pipes and shafts are widely used in various industrial facilities. Recently, researches on magnetostrictive transduction of torsional waves have been actively reported for the nondestructive evaluation of those cylindrical structures. However, the existing magnetostrictive patch transducer has somewhat inconvenient and time.consuming process like patch bonding to a structure since it should employ a magnetostrictive patch having strong magnetostriction. To overcome these limitations of the existing transducer, in this work, we develop a novel modular magnetostrictive transducer to generate and measure torsional waves to inspect a cylindrical structure. The proposed transducer can be applied as viscous liquid coupling with shear couplant or dry coupling without coupling media instead of patch bonding to a structure. We describe a detailed structure of the modular transducer and conduct some experiments to verify its performance.
Experimental Analysis on Vibration of Composite Plate by Using FBG Sensor System
Kim, Dae-Hyun ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 5, 2009, Pages 436~441
A fiber optic sensor is prospective to be applied to structural health monitoring. Especially, a fiber Bragg grating(FBG) sensor is one of the most popular sensors for the structural health monitoring. The FBG sensor has several demodulation systems for tracking the shift of the Bragg wavelength. The dynamic bandwidth is dependent on the demodulation system. In this paper, the sensing mechanism is that the slope of the optical spectrum of FBG could be used as its sensitivity when the tunable laser shot the monochromatic laser wavelength at the highest slope point. In this technique, the high sensitivity is guaranteed even though the sensing range is limited. In an example of the application, the composite plate embedding a FBG sensor was manufactured by using an autoclave method and the above sensing mechanism was applied to the composite plate. Firstly, the natural frequencies of the plate were successfully measured by the FBG sensor during the impact hammer test. Secondly, a high-power speaker was used to force the plate to be vibrated at the specific frequency that was one of the natural frequencies. During the shaking, the FBG sensor measures the dynamic characteristics and ESPI was also used to measure the mode shape. From the two dynamic tests, the availability of the FBG sensor system and the ESPI was proven as a technique for measuring the dynamic characteristics of composite structure.
A Study on MsS Guided Wave Scattering from Defects
Choi, Boo-Il ; Cho, Youn-Ho ; Lee, Joon-Hyun ; Shin, Dong-Chul ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 5, 2009, Pages 442~449
An investigation has been made on the relationship between characteristics of torsional mode signal in MsS and SH mode signal in BEM modeling for the defect of stainless steel pipe. In order to compare torsional mode signal with SH mode signal of defect in stainless steel pipe, specimens were made by changing size of depth and width along to circumferential direction 360 degrees. All the defects was detected by torsional mode signal of MsS, especially according to the change of depth size, amplitude of signal was changed. But width change for the circumferential defects has no certain tendency. SH mode signal of BEM modeling shows similar results with torsional mode, with change makes amplitude variation of signal. In this paper, the characteristics of torsional mode and SH mode signals were found. It is possible to predict the circumferential defects for the pipe by SH mode modeling.
Evaluation of Defects of Thermal Barrier Coatings by Thermal Shock Test Using Eddy Current Testing
Heo, Tae-Hoon ; Cho, Youn-Ho ; Lee, Joon-Hyun ; Oh, Jeong-Seok ; Lee, Koo-Hyun ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 5, 2009, Pages 450~457
Periodical thermal shock can introduce defects in thermal barrier coating made by layers of CoNiCrAlY bond coating(BC) and
ceramic top coating(TC) on Inconel-738 substrate using plasma spraying. Thermal shock test is performed by severe condition that is to heat until
and cool until
. As the number of cycle is increased, the fatigue by thermal shock is also increased. After test, the micro-structures and mechanical characteristics of thermal barrier coating were investigated by SEM, XRD. The TGO layer of
is formed between BC and TC by periodical thermal shock test, and its change in thickness is inspected by eddy current test(ECT). By ECT test, it is shown that TGO and micro-crack can be detected and it is possible to predict the life of thermal barrier coating.
Experimental Investigation for the Attenuation Coefficient of Ultrasonic Guided Wave
Lee, Dong-Jin ; Cho, Youn-Ho ; Lee, Joon-Hyun ; Shin, Dong-Chul ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 5, 2009, Pages 458~465
In general, ultrasonic guided wave techniques that used for an evaluation of the internal defect have been applied without considering energy loss. It can be found out that the significant attenuation is observed in the signal of structure with defect by the scattering and absorption. Even in the signal acquired from defect-free structure, this attenuation can be also significant. Therefore, it is very essential to determine the Lamb wave propagation characteristics depending on modes because the dispersibility of Lamb wave can be easily influenced by the attenuation effect with frequency and thickness. For this reason, changing the propagation distance, attenuation coefficient of each Lamb wave mode needs to be investigated by the contact pitch-catch method with PZT(piezoelectric) sensors. In this paper, the experimental attenuation coefficient is measured by choosing the following three different variables; mode, thickness and plate materials. As a result, experimental attenuation coefficient is obtained as the function of variables.
A Study on the Leakage Characteristic Evaluation of High Temperature and Pressure Pipeline at Nuclear Power Plants Using the Acoustic Emission Technique
Kim, Young-Hoon ; Kim, Jin-Hyun ; Song, Bong-Min ; Lee, Joon-Hyun ; Cho, Youn-Ho ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 5, 2009, Pages 466~472
An acoustic leak monitoring system(ALMS) using acoustic emission(AE) technique was applied for leakage detection of nuclear power plant's pipeline which is operated in high temperature and pressure condition. Since this system only monitors the existence of leak using the root mean square(RMS) value of raw signal from AE sensor, the difficulty occurs when the characteristics of leak size and shape need to be evaluated. In this study, dual monitoring system using AE sensor and accelerometer was introduced in order to solve this problem. In addition, artificial neural network(ANN) with Levenberg.Marquardt(LM) training algorithm was also applied due to rapid training rate and gave the reliable classification performance. The input parameters of this ANN were extracted from varying signal received from experimental conditions such as the fluid pressure inside pipe, the shape and size of the leak area. Additional experiments were also carried out and with different objective which is to study the generation and characteristic of lamb and surface wave according to the pipe thickness.
Study on Evaluation of Plastic Deformation Zone at Crack Tip for the Multi-Passed Weld Region of the Pressure Vessel Steel Using Nondestructive Method
Na, Eui-Gyun ; Lee, Sang-Guen ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 5, 2009, Pages 473~478
The purpose of this study is to evaluate the behaviour of the plastic deformed zone at crack tip on the standard Charpy specimens which were taken from the multi-passed weld block of the pressure vessel steel. Notch was machined on the standard Charpy test specimens and pre-crack which was located around the fusion line was made under the repeat load. Four point bend and acoustic emission tests were carried out simultaneously. The size of plastic region at crack tip was calculated using stress intensity factor. Relationships between characteristics of acoustic emission and plastic zone size at crack tip were discussed through the cumulative AE energy. Regardless of the specimens, AE signals were absent within the elastic region almost and most of AE signals were produced at the plastic deformation region from yield point to the mid-point between yield and maximum load. More AE signals for the weldment were produced compared with the base-metal and PWHT specimen. Relations between plastic deformed zones at crack tip and cumulative AE energy for the weldment and PWHT specimen were different quietly from the base-metal. Besides, number of AE counts for the weldment was the larger than those of the base-metal and PWHT specimen.
A Feasibility Study on the Application of Ultrasonic Method for Surface Crack Detection of SiC/SiC Composite Ceramics
Nam, Ki-Woo ; Lee, Kun-Chan ; Kohyama, Akira ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 5, 2009, Pages 479~484
Nondestructive evaluation(NDE) of ceramic matrix composites is essential for developing reliable ceramics for industrial applications. In the work, C-Scan image analysis has been used to characterize surface crack of SiC ceramics nondestructively. The possibility of detection of surface crack were carried out experimentally by two types of ultrasonic equipment of SDS-win and
-SDS, and three types of transducer of 25, 50 and 125 MHz. A surface micro-crack of ceramics was not detected by transducer of 25 MHz and 50 MHz. Though the focus method was detected dimly the crack by transducer of 125 MHz, the defocus method could detect the shape of diamond indenter. As a whole, the focus method and the defocus method came to the conclusion that micro crack have a good possibility for detection.
The Basic Study on the Method of Acoustic Emission Signal Processing for the Failure Detection in the NPP Structures
Kim, Jong-Hyun ; Korea Aerospace University, Jae-Seong ; Lee, Jung ; Kwag, No-Gwon ; Lee, Bo-Young ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 5, 2009, Pages 485~492
The thermal fatigue crack(TFC) is one of the life-limiting mechanisms at the nuclear power plant operating conditions. In order to evaluate the structural integrity, various non-destructive test methods such as radiographic test, ultrasonic test and eddy current are used in the industrial field. However, these methods have restrictions that defect detection is possible after the crack growth. For this reason, acoustic emission testing(AET) is becoming one of powerful inspection methods, because AET has an advantage that possible to monitor the structure continuously. Generally, every mechanism that affects the integrity of the structure or equipment is a source of acoustic emission signal. Therefore the noise filtering is one of the major works to the almost AET researchers. In this study, acoustic emission signal was collected from the pipes which were in the successive thermal fatigue cycles. The data were filtered based on the results from previous experiments. Through the data analysis, the signal characteristics to distinguish the effective signal from the noises for the TFC were proven as the waveform difference. The experiment results provide preliminary information for the acoustic emission technique to the continuous monitoring of the structure failure detection.
Ultrasonic Signal Processing Algorithm for Crack Information Extraction on the Keyway of Turbine Rotor Disk
Lee, Jong-Kyu ; Seo, Won-Chan ; Park, Chan ; Lee, Jong-O ; Son, Young-Ho ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 5, 2009, Pages 493~500
An ultrasonic signal processing algorithm was developed for extracting the information of cracks generated around the keyway of a turbine rotor disk. B-scan images were obtained by using keyway specimens and an ultrasonic scan system with x-y position controller. The B-scan images were used as input images for 2-Dimensional signal processing, and the algorithm was constructed with four processing stages of pre-processing, crack candidate region detection, crack region classification and crack information extraction. It is confirmed by experiments that the developed algorithm is effective for the quantitative evaluation of cracks generated around the keyway of turbine rotor disk.