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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 20, Issue 6 - Dec 2000
Volume 20, Issue 5 - Oct 2000
Volume 20, Issue 4 - Aug 2000
Volume 20, Issue 3 - Jun 2000
Volume 20, Issue 2 - Apr 2000
Volume 20, Issue 1 - Feb 2000
Selecting the target year
Evaluation of fracture Appearance Transition Temperature to Pressure Vessel by Ultrasonics
Nam, Young-Hyun ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 5, 2000, Pages 373~380
It is useful to use NDE methods to assess the mechanical properties of materials since destructive methods are time-consuming and usually require cutting of sample from the material/component. In the present research, ultrasonic characteristics have been utilized to evaluate changes of mechanical properties due to heat treatment temperature and condition. The attenuation coefficient of ultrasonic wave increased as the heat treatment temperature because the grain size increased in size as the temperature. The attenuation coefficient decreased as the heat treatment has been progressed (quenched, tempered, PWHT). In the case of ultrasonic velocity measurement, velocity difference between quenched and tempered/PWHT was 40 m/s. There was a good relationship between the attenuation coefficient and the toughness. The relationship can be used for the nondestructive evaluation of the forged reactor vessels. Moreover, the method may be effectively used in the field application.
Evaluation of Microscopic Deformation Behaviors of Metal Matrix Composite due to Heat Treatment by means of SFC Test and Acoustic Emission
Kang, Moon-Phil ; Lee, Joon-Hyun ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 5, 2000, Pages 381~389
Metal matrix composite(MMCs) have been rapidly becoming one of the strongest candidates for structural materials for high temperature application. It is well recognized that MMCs always experience at least one large cool-down from processing temperature before my significant applied service loading. Due to the large difference in thermal expansion coefficient between the fiber and matrix, large thermal residual stresses generally develop in composites. It was reported from many previous studies that the effects of thermal residual stress on mechanical properties and fracture behavior were much more complex and dramatic than conventional engineering materials. Therefore it is crucial to evaluate the effect of heat treatment which changes the characteristic of distribution of thermal residual stress in MMCs. Single fiber composite(SFC) test based on the balance in a micromechanical model is a quite convenient method to evaluate interfacial shear strength(IFSS) and the failure mode of composite. In this study the effect of heat treatment on IFSS and the microscopic failure mechanism of MMC is investigated by combining acoustic emission(AE) technique with SFC test. The characteristic of AE signal, IFSS and microscopic failure mechanism due to heat treatment condition is discussed.
Measurement of Dynamic Elastic Constants of RPV Steel Weld due to Localized Microstructural Variation
Cheong, Yong-Moo ; Kim, Joo-Hag ; Hong, Jun-Hwa ; Jung, Hyun-Kyu ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 5, 2000, Pages 390~396
The dynamic elastic constants of the simulated weld HAZ (heat-affected zone) of SA 508 Class 3 reactor pressure vessel (RPV) steel were investigated by resonant ultrasound spectroscopy (RUS). The resonance frequencies of rectangular parallelepiped samples woe calculated from the initial estimates of elastic stiffness
with an assumption of isotropic property, dimension and density. Through the comparison of calculated resonant frequencies with the measured resonant frequencies by RUS, very accurate elastic constants of SA 508 Class 3 steel were determined by iteration and convergence processes. Clear differences of Youngs modulus and shear modulus were shown from samples with different thermal cycles and microstructures. Youngs modulus and shear modulus of samples with fine-grained bainite were higher than those with coarse-grained tempered martensite. This tendency was confirmed from other results such as micro-hardness test.
Evaluation of Corrosion Fatigue Characteristics of 12Cr Steel Using Backward Radiated Ultrasound
Kwon, Sung-Duk ; Yoon, Seok-Soo ; Song, Sung-Jin ; Bae, Dong-Ho ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 5, 2000, Pages 397~401
The corrosion-fatigue characteristics of the 12Cr steel, which is widely used in fossil power plants as a turbine blade material, are evaluated nondestructively by use of the Rayleigh surface wave. In this study, the frequency dependency of the Rayleigh surface wave is investigated indirectly by measuring the angular dependency of the backward radiation of the incident ultrasonic wave in the aged specimens, and then compared to the corrosion-fatigue characteristics. The width of the backward radiation profile decreases as the increase of the aging temperature, which seems to result from the increase of the effective degrading layer thickness. This parameter also shows an inversely proportionality to the exponent, m, in the Paris law which predicts the crack size increasement due to fatigue. The result observed in this study demonstrates high potential of the backward radiated ultrasound as a tool for the nondestructive evaluation of the corrosion-fatigue characteristics of the aged materials.
Viscoelastic Property Evaluation of Asphalt Cement by Ultrasonic Measurement
Lee, Jai-Hak ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 5, 2000, Pages 402~411
This study investigates the method to measure the viscoelastic properties of asphalt cement, one of the viscoelastic materials, using the ultrasound. The wave speed and attenuation were measured from
at the frequency of 2.25MHz. Then, the storage and loss longitudinal moduli, loss tangent storage and loss longitudinal compliances were found depending on the temperatures based on the linear viscoelastic theory. Stress relaxation, creep, and viscosity were predicted using Maxwell and Voigt-Kelvin viscoelastic models. The validity of superposition principle and shift factor were verified by comparing the present results to the data reported in the literatures.
Study on the Fatigue Crack Behavior by the Stress Intensity Factor and AE Parameters
Yoon, Dong-Jin ; Jeong, Jung-Chae ; Park, Phi-Lip ; Kim, Ki-Bok ; Lee, Seung-Seok ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 5, 2000, Pages 412~423
By using the relation between stress intensity factor and AE parameter, new approach method for assessing the crack length and detectability of crack was proposed. Laboratory experiment was carried out to identify AE characteristics of fatigue cracks for compact tension specimen. The relationship between a stress intensity factor and AE signals activity as well as conventional AE parameter analysis was discussed. As a result, the features of specific parameter such as the length of crack growth the AE energy, the AE peak amplitude, and the cumulative AE hits, showed the almost same trend in their increase as the number of fatigue cycle increased. From the comparisons of peak amplitude and AE energy with stress intensity factor, it was verified that the higher stress intensity factors generated AE signals with higher peak amplitude and a larger number of AE counts. If we can get more reliable database for the relation between AE parameters and stress intensity factor, this approach will provide a good information for evaluating both the existence of crack and the minimum detectable size of crack.
Estimation of Fracture Toughness Degradation of High Temperature Materials by Nonlinear Acoustic Effects
Jeong, Hyun-Jo ; Nahm, Seung-Hoon ; Jhang, Kyung-Young ; Nam, Young-Hyun ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 5, 2000, Pages 424~430
In order to develop an ultrasonic evaluation method for properties degradation of high temperature materials, a number of Cr-Mo-V steel samples were heat-treated and their damage mechanism was examined. Ultrasonic parameters such as velocity, attenuation, and more recently developed nonlinear acoustic parameter were measured. The nonlinear acoustic parameter was found to be most sensitive to material degradation mainly attributed to the precipitation of impurities in grain boundaries. When compared to the electrical resistivity results, the nonlinear parameters showed similar behavior. There existed a relatively good correlation between the nonlinear parameter and the fracture appearance transition temperature (FATT) obtained by Charpy V-notch impact test. Based on the relationship between the FATT and the fracture toughness (
), correlation between the nonlinear parameter and
Evaluation of Suitability of Non-Standardized Test Block for Ultrasonic Testing
Kwon, Ho-Young ; Lim, Jong-Ho ; Kang, Sei-Sun ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 5, 2000, Pages 431~437
Standard Test Block(STB) for UT(Ultrasonic Testing) is a block approved by authoritative for material, shape and quality. STB is used for characteristic tests, sensitivity calibration and control of the time base range of UT inspection devices. The material, size and chemical components of STB should be strictly controled to meet the related standards such as ASTM and JIS because it has an effect upon sensitivity, resolution and reproductivity of UT. The STBs which are not approved are sometimes used because the qualified STBs are very expensive. So, the purpose of this study is to survey the characteristics, quality and usability of Non-Standardized Test Blocks. Non-Standardized Test Blocks did not meet the standard requirements in size or chemical components, and ultrasonic characteristics. Therefore if the Non-Standardized Test Blocks are used without being tested, it's likely to cause errors in detecting the location and measuring the size of the defects.
The Evaluation of Mechanical Property of WC-8%Co Alloys by Coercive Force and Magnetic Saturation
Ahn, Dong-Gil ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 5, 2000, Pages 438~444
The prediction of mechanical properties for WC-Co alloys by evaluation of coercive force and magnetic saturation were studied in relation to their microstructure. The WC-8%Co alloys were prepared using different WC particle size, carbon content and various sintering temperature by PM process. The magnetic properties such as coercive force and magnetic saturation of sintered WC-Co alloys were critically dependent upon their final composition and microstructure. Slight changes of carbon contents and small variation of WC grain size result in marked changes of magnetic properties, hardness and transverse rupture strength of sintered WC-Co alloys. It was found that the coercive force and hardness were increased by fine WC grain size of sinterd alloys, and the coercive force was proportional to hardness. With decreasing total carbon content below the stoichiometric value in WC-8%Co alloys the volume fraction of
phase increased steadily, while the magnetic saturation and transverse rupture strength decreased. The magnetic saturation was inversely proportional to the coercive force of WC-Co alloys.
Degradation Evaluation of 1Cr-lMo-0.25V Steel by Measuring Reversible Magnetic Permeability
Ryu, Kwon-Sang ; Kim, Yong-Il ; Nahm, Seung-Hoon ; Yu, Kwang-Min ; Cho, Youk ; Son, De-Rac ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 5, 2000, Pages 445~450
The integrity of the turbine rotors can be assessed by measuring reversible permeability and Vickers hardness of the aged rotors at service temperature. The measurement system of reversible permeability, which measured by applied alternating perturbing magnetic field, was constructed in order to evaluate material degradation, nondestructively. The test specimen was 1Cr-1Mo-0.25V steel used widely for turbine rotor material, and the specimens were prepared by the isothermal heat treatment at
. The reversible permeability of the test materials were measured at room temperature. The peak interval of reversible permeability and Vickers hardness decreased with the increase of degradation. The degradation of test material may be determined nondestructively by the lineality of Vickers hardness and the peak interval of reversible permeability.
Fabrication and Use of Corrosion Defect Specimens for Enhancement of ECT Reliability for Nuclear Steam Generator Tubing
Hur, Do-Haeng ; Choi, Myung-Sik ; Lee, Doek-Hyun ; Park, Jung-Am ; Han, Jung-Ho ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 5, 2000, Pages 451~456
The development of an integrated technology including fabrication of corrosion defect specimens and their practical use is needed to enhance the reliability of eddy current test for nuclear steam generator tubing. In this paper, the necessity and importance are presented from the viewpoint of the structural integrity, simulation specimens for real defects, and experiences from the destructive examination of pulled tubes. The models for several corrosion defects we also briefly introduced, with the scheme for their practical use.