Go to the main menu
Skip to content
Go to bottom
REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Journal of the Korean Society for Nondestructive Testing
Journal Basic Information
Journal DOI :
The Korean Society for Nondestructive Testing
Editor in Chief :
Volume & Issues
Volume 23, Issue 6 - Dec 2003
Volume 23, Issue 5 - Oct 2003
Volume 23, Issue 4 - Aug 2003
Volume 23, Issue 3 - Jun 2003
Volume 23, Issue 2 - Apr 2003
Volume 23, Issue 1 - Feb 2003
Selecting the target year
Nondestructive Evaluation of Remanent Life of Turbine Rotor Steel by Measuring Reversible Magnetic Permeability
Ryu, Kwon-Sang ; Nahm, Seung-Hoon ; Kim, Yong-Il ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 4, 2003, Pages 315~321
The integrity of the turbine rotors can be assessed by measuring the material properties at service temperature. In order to evaluate the remanent life of turbine rotor steel nondestructively, a measurement system of reversible magnetic permeability using an alternating perturbing magnetic field was constructed. We present a new non-destructive method to evaluate the remanent life of 1Cr-1Mo-0.25V steel using the value of reversible magnetic permeability. This method is based on the existence of reversible magnetic permeability in the differential magnetization around the coercive field strength. We measured the first harmonics voltage induced in a coil using a lock-in amplifier tuned to an exciting frequency. The Results of reversible magnetic Permeability and Wickers hardness on the aged samples show that the peak interval of reversible magnetic permeability (PIRMP) and Vickers hardness decreases as aging time increases. A softening curve is obtained from the correlation between Vickers hardness and the PIRMP. This curve can be used as a non-destructive method to evaluate the remanent life of turbine rotor steel.
The Effect of Residual Stress on Magnetoresistance in GMR Head Multilayers
Hwang, Do-Guwn ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 4, 2003, Pages 322~327
Giant magnetoresistance(GMR) NiO multilayer, which has been used to reading head of highly dense magnetic recording, was fabricated, and oxidized in an air during 80 days to study the dependence of magnetoresistance properties on residual stress in the interfaces. The magnetoresistance ratio and the exchange biasing
spin valves were increased from 4.9% to 7.3%, and 110 Oe to 170 Oe after natural oxidation in the atmosphere for 80 days, respectively. The sheet resistivity
did not almost change after the oxidation. Therefore, the increase of MR ratio is due to the decrease in the sheet resistivity. the reduced resistance may result from the increase in the reflection of conduction electrons at the oxidized top surface. Also, the increase in the exchange biasing field is originated from the reduction of residual stress at the interface of
according as the aging time increases.
A Study on the Comparative Evaluation of Welding Residual Stresses of Pipes in Power Plants using Saw-rutting and Indentation Methods
Choi, Won-Doo ; Lee, Sang-Guk ; Lee, Young-Ho ; Gil, Doo-Song ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 4, 2003, Pages 328~333
It has been widely recognized that the residual stress of the weldment affect the integrity of steel structures and cause an initiation of crack in the welded regions. Since the power plants adopt a variety of welding processes, it is necessary to know the distribution and magnitude of residual stresses. This paper has attempted to investigate the validity of the saw cutting method and the indentation method to measure the residual stresses in the steel plates. The residual stresses in the specimens of hot reheater pipes, cold reheater pipes and feed water lines in power plants were determined by the saw cutting method and the indentation method. The data were compared and reviewed for the validity of the methods.
Detection of Hydride Blisters in Zirconium Pressure Tubes using Ultrasonic Mode Conversion and Velocity Ratio Method
Cheong, Yong-Moo ; Lee, Dong-Hoon ; Kim, Young-Suk ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 4, 2003, Pages 334~341
When the pressure tubes(f are in contact with the calandria tube(CT) in the pressurized heavy water reactor(PHWR), the temperature difference between inner and outer wall of W results in a thermal diffusion of hydrogen (deuterium) and hydride blisters are formed on the outer surface of PT. Because the hydride blisters and zirconium matrix are acoustically continuous, it is not easy to distinguish the blisters from the matrix with conventional ultrasonic method. An ultrasonic velocity ratio method was developed to detect small hydride blisters on the zirconium pressure tube. Hydride blisters were grown in the PT specimen using a steady state thermal diffusion device. The flight times of longitudinal echo and reflected shear echo from the outer surface were measured accurately. The velocity ratio of the longitudinal wave to the shear wave was calculated and displayed using contour plot. Compared to the conventional flight time method of longitudinal wave, the velocity ratio method shows superior sensitivity to detect smaller blisters as well as better images for the blister shapes. Detectable limit of the outer shape of the hydride blisters was conservatively estimated as
, with the same specifications of ultrasonic transducer used in the actual PHWR pressure tube inspection.
Ultrasonic Backscattering Profiles from Zirconium Plate with Beryllium Diffusion Layer
Hwang, Y.H. ; Choi, H.O. ; Park, C.H. ; Lee, Y.H. ; Kwon, S.D. ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 4, 2003, Pages 342~348
Ultrasonic backscattering profiles of the Zr plates(with a thickness of 1.32mm) with/without Be-Zr alloy layer(with a thickness of
) were measured at various incidence positions to evaluate the characteristics of Be diffusion layer. Four principal subprofiles were observed in the backward ultrasound radiated from leaky Lamb waves. The angles and the intensities of the subprofile peaks decreased by the stiffening effect of Be layer. Generation and change of the subprofiles were explained by the acoustical property, collective group velocity and leaky factor difference of the plates under consideration. Backward radiation subprofiles turned out to be an useful method for evaluating thin diffusion layers on plates.
Assessment of Degradation by Corrosion Fatigue of TMCP Steel using a Backward Radiated Ultrasound
Kim, Y.H. ; Bae, D.H. ; Park, J.H. ; Yu, H.J. ; Kwon, S.D. ; Song, S.J. ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 4, 2003, Pages 349~355
Material degradation due to corrosion fatigue was evaluated nondestructively using backward radiated Rayleigh surface wave. h corrosion fatigue test was carried out for the specimens made of thermo-mechanically controlled process steel in 3.5wt.% NaCl solution at
. The backward radiation profile, which is the amplitude variation of backward radiated ultrasound according to the incident angle, of the specimens were measured in water at room temperature after the corrosion fatigue test. The velocity of Rayleigh surface wave, determined from the incident angle at which the profile of the backward radiated ultrasound became maximum, decreased for the specimen that had the large number of cycles to failure in the corrosion fatigue test. This fact implies that the corrosion degradation occurred at specimen surface in this specific test is dominantly dependant on the me exposed to corrosion environment. The result observed in the present work demonstrates the high potential of backward radiated Rayleigh surface wave as a tool for nondestructive evaluation of corrosion degradation of aged materials.
Development of Eddy Current Testing System using Magnetic Saturation in ferromagnetic Materials
Sung, Je-Joong ; Shin, Young-Hoon ; Um, Tae-Gun ; Kang, Seok-Chul ; Kweon, Young-Ho ; Suh, Dong-Man ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 4, 2003, Pages 356~363
An eddy current testing system was developed for detection of flaws in the ferromagnetic steel tubes. Because the eddy current signals from the ferromagnetic steel tubes could be distorted easily due to an irregularity of magnetic permeability, magnetic saturation is required to suppress this variation of magnetic fields. A magnetic saturation probe with the Hemholtz coil was designed for the inspection of the steel tubes. The bandwidth pass filters were adapted to minimize the noise from the DC magnetization. When using the designed test probe, the flaw signals could be discriminated from the noise. The system was tested at the production line and showed a capability of detecting flaws, like a drilled hole of the diameter of 2.0mm at the moving speed of 1m/sec.
Long Range Cylindrically Guided Ultrasonic Wave Technique for Inspection
Balasubramaniam, Krishnan ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 4, 2003, Pages 364~371
In this paper, a review of the current status, on the use of long range cylindrically guided wave modes, and their interaction with cracks and corrosion damage in pipe-like structures will be discussed. Applications of cylindrically guided ultrasonic wave modes have been developed for inspection of corrosion damage in pipelines at chemical plants, flow-accelerated corrosion damage (wall thinning) in feedwater piping, and circumferential stress corrosion cracks in PWR steam generator tubes. It has been demonstrated that this inspection technique can be employed on a variety of piping geometries (diameters from 1 in. to 3 ft, and wall thickness from 0.1 to 6 in.) and a propagation distance of 100 meters or more is sometimes feasible. This technique can also be used in the inspection of inaccessible or buried regions of pipes and tubes.
Ultrasonic Examination of Thick Austenitic Stainless Steel Welds and Factors Influence the Sensitivity
Palaniappan, M. ; Subbaratnam, R. ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 4, 2003, Pages 372~379
The problems encountered by ultrasonic testing of austenitic stainless steel weld joints are discussed in the paper. Due to low thermal conductivity and the occurrence of single phase between the melting point and the room temperature, coarse and oriented grains are formed in such weld metals more in thick sections. This leads to higher scattering at the grain boundaries and low signal to noise ratio, and extensive beam skewing. Experimental results to understand these problem are explained.
Nondestructive Evaluation of Structural Materials using Micromagnetic Methods
Park, Deuk-Gun ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 4, 2003, Pages 380~387