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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 31, Issue 6 - Dec 2011
Volume 31, Issue 5 - Oct 2011
Volume 31, Issue 4 - Aug 2011
Volume 31, Issue 3 - Jun 2011
Volume 31, Issue 2 - Apr 2011
Volume 31, Issue 1 - Feb 2011
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Measurements of Sub- and Super Harmonic Waves at the Interfaces of Fatigue-Cracked CT Specimen
Jeong, Hyun-Jo ; Barnard, Dan ;
Journal of the Korean Society for Nondestructive Testing, volume 31, issue 1, 2011, Pages 1~10
Nonlinear harmonic waves generated at cracked interfaces are investigated both experimentally and theoretically. A compact tension specimen is fabricated and the amplitude of transmitted wave is analyzed as a function of position along the fatigued crack surface. In order to measure as many nonlinear harmonic components as possible a broadband Lithium Niobate (
) transducers are employed together with a calibration technique for making absolute amplitude measurements with fluid-coupled receiving transducers. Cracked interfaces are shown to generate high acoustic nonlinearities which are manifested as harmonies in the power spectrum of the received signal. The first subharmonic (f/2) and the second harmonic (2f) waves are found to be dominant nonlinear components for an incident toneburst signal of frequency f. To explain the observed nonlinear behavior a partially closed crack is modeled by planar half interfaces that can account for crack parameters such as crack opening displacement and crack surface conditions. The simulation results show reasonable agreements with the experimental results.
Numerical Simulation of Electro-Mechanical Impedance Response in Cable-Anchor Connection Interlace
Nguyen, Khac-Duy ; Kim, Jeong-Tae ;
Journal of the Korean Society for Nondestructive Testing, volume 31, issue 1, 2011, Pages 11~23
In this study, a finite element(FE) analysis on electro-mechanical impedance response of cable-anchor connection interface under various anchor force is presented. In order to achieve the objective, the following approaches are implemented. Firstly, an interface washer coupled with piezoelectric(PZT) material is designed for monitoring cable-force loss. The interface washer is a small aluminum plate on which a PZT patch is surface-bonded. Cable-force loss could be monitored by installing the interface washer between the anchor plate and the anchorage of cable-anchor connection and examining the changes of impedance of the interface washer. Secondly, a FE model for cable-anchor connection is established to examine the effect of cable-force on impedance response of interface washer. Also, the effects of geometrical and material properties of the interface washer on impedance responses under various cable-forces are investigated. Finally, validation of the FE analysis is experimentally evaluated by a lab-scale cable-anchor connection.
Corrosion Level Measurement Technique for RC Reinforcement Using Non-Destructive Test Methods
Roh, Young-Sook ;
Journal of the Korean Society for Nondestructive Testing, volume 31, issue 1, 2011, Pages 24~31
In order to measure corrosion level of reinforcement rebar in RC structures, non-destructive test methods which are concrete surface current density method and infrared thermographic technique were employed to measure corrosion levels. Experimental test parameters were various levels of corrosion states(0, 1, 3, 5, 7% of weight loss) and concrete cover depth(30 mm, 40 mm) and two different reinforcing rebar arrangements. The larger amount of concrete surface current density, the higher corrosion level in reinforcement rebar. The laboratory conditions which are ambient temperature and humidity have negligible effect on the infrared thermographical data. After analysis of current density and temperature distribution from concrete surface, corrosion level of reinforcement rebar embedded in concrete can be measured qualitatively based on the amount of electric current and heat flux.
Nondestructive Techniques for Characterization of Microstructural Evolution during Low Cycle Fatigue of Cu and Cu-Zn Alloy
Kim, Chung-Seok ; Jhang, Kyung-Young ; Hyun, Chang-Young ;
Journal of the Korean Society for Nondestructive Testing, volume 31, issue 1, 2011, Pages 32~39
The object of this study is to evaluate and discriminate nondestructively the dislocation substructures of Cu and Cu-Zn alloy subjected to the low-cycle-fatigue. The ultrasonic wave velocity, electrical resistivity and positron annhilation lifetime(PAL) were measured to the nondestructive testing. Cyclic fatigue test of Cu and Cu-Zn alloy with much different stacking fault energies was conducted and the correlations between dislocation behavior and nondestructive parameters were studied. Dislocation cell substructure was developed in Cu, while planar array of dislocation structure was developed in Cu-35Zn alloy only increasing dislocation density with fatigue cycles. Decrease in ultrasonic wave velocity, increase in electrical resistivity and PAL were shown because of the development of lattice defects, dislocations and vacancies, by cyclic fatigue at room temperature. In contrast to Cu-Zn alloy of the planar-array dislocation substructure showing continuous changes in the nondestructive parameters, it does not make any noticeable changes in the nondestructive parameters after the evolution of dislocation cell substructure in Cu.
Acoustic Nonlinear Characteristics of Ultrasonic Wave Reflected at Contact Interfaces
Park, Byung-Jun ; Lee, Tae-Hun ; Kim, Chung-Seok ; Jhang, Kyung-Young ;
Journal of the Korean Society for Nondestructive Testing, volume 31, issue 1, 2011, Pages 40~46
In the field application of the conventional acoustic nonlinear technique using through transmission of bulk waves to evaluate the contact acoustic nonlinearity(CAN) in solid-solid contact interfaces like as in the closed crack, it has difficulty to access inner position for attaching the pulsing or receiving transducer. In the present study, a new reflection technique has been suggested to measure the acoustic nonlinearity in solid-solid contact interfaces, which uses both of pulsing and receiving transducers on the same side of target and so that it will be very useful for the field application. For this, based on the linear and the nonlinear contact stiffness estimated by the power-model of the contacting pressure, the nonlinear parameter of the reflected ultrasonic wave at the interfaces has been theoretically calculated. Experimental results in contact interfaces of A1606l-T6 alloy specimens with loading pressure showed good agreement with the theoretical predictions, which proves the validity of the suggested reflection mode technique.
Evaluation of Thickness Reduction in Steel Plate by Using SH-EMATs
Lee, Jin-Hyuk ; Park, Ik-Keun ; Kim, Yong-Kwon ; Kim, Dae-Hyun ;
Journal of the Korean Society for Nondestructive Testing, volume 31, issue 1, 2011, Pages 47~52
An electromagnetic acoustic transducer(EMAT) is a non-contact transducer which can transmit the ultrasonic guided waves into specimens without couplant. And it can easily generate specific guided waves such as SH(shear horizontal) or Lamb waves by altering the design of coil and magnet. In this study, the SH wave, which is generated by EMAT, has been applied to estimate the thickness-reduction in a steel plate. Especially, the interesting feature of the dispersive behavior in selected wave modes is used to detect the thickness-reduction. Experimental results show that the reduction-level can be quantified by the measurement of the group velocity of the wave which passes though the thinning area.
Acoustic Emission Characteristics of Notched Aluminum Plate Repaired with a Composite Patch
Yoon, Hyun-Sung ; Choi, Nak-Sam ;
Journal of the Korean Society for Nondestructive Testing, volume 31, issue 1, 2011, Pages 53~61
Edge notched A16061-T6 aluminum was repaired with a GFRP composite patch as a function of the number of stacking, Damage progress of specimen for tension load has been monitored by acoustic emission(AE), AE energy rate, hit rate, amplitude, waveform and 1st peak frequency distribution were analyzed. Fracture processes were classified into Al cracking, Fiber breakage, Resin cracking and Delamination. Displacement of a specimen can be divided into Region I, II and ill according to acoustic emission characteristics. Region II where the patch itself was actually fractured was focused on to clarify the AE characteristics difference for the number of stacking.
Acoustic Emission Monitoring of Compression-after-Impact Test of Nano-Particles-Coated CFRP Damaged by Simulated Lightning Strikes
Shin, Jae-Ha ; Kwon, Oh-Yang ; Seo, Seong-Wook ;
Journal of the Korean Society for Nondestructive Testing, volume 31, issue 1, 2011, Pages 62~67
Nanoparticles-coated and impact-damaged carbon-fiber reinforced plastics(CFRP) laminates were tested under compression-after-impact(CAI) mode and the propagation of damage due to compressive loading has been monitored by acoustic emission(AE). The impact damage was induced not by mechanical loading but by a simulated lightning strike. CFRP laminates were made of carbon prepregs prepared by coating of conductive nano-particles directly on the fibers and the coupons were subjected to simulated lightning strikes with a high voltage/current impulse of 10~40 kA within a few microseconds. The effects of nano-particles coating and the degree of damage induced by the simulated lightning strikes on the AE activities were examined, and the relationship between the compressive residual strength and AE behavior has been evaluated in terms of AE event counts and the onset of AE activity with the compressive loading. The degree of impact damage was also measured in terms of damage area by using ultrasonic C-scan images. From the results assessed during the CAI tests of damaged CFRP showed that AE monitoring appeared to be very useful to differentiate the degree of damage hence the mechanical integrity of composite structures damaged by lightning strikes.
Damage Detection Method of Wind Turbine Blade Using Acoustic Emission Signal Mapping
Han, Byeong-Hee ; Yoon, Dong-Jin ;
Journal of the Korean Society for Nondestructive Testing, volume 31, issue 1, 2011, Pages 68~76
Acoustic emission(AE) has emerged as a powerful nondestructive tool to detect any further growth or expansion of preexisting defects or to characterize failure mechanisms. Recently, this kind of technique, that is an in-situ monitoring of inside damages of materials or structures, becomes increasingly popular for monitoring the integrity of large structures like a huge wind turbine blade. Therefore, it is required to find a symptom of damage propagation before catastrophic failure through a continuous monitoring. In this study, a new damage location method has been proposed by using signal mapping algorithm, and an experimental verification is conducted by using small wind turbine blade specimen; a part of 750 kW real blade. The results show that this new signal mapping method has high advantages such as a flexibility for sensor location, improved accuracy, high detectability. The newly proposed method was compared with traditional AE source location method based on arrival time difference.