• Journal of the Korean Society for Nondestructive Testing
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• v.10 no.2
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• pp.38-42
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• 1990

The specific strength of the fiber reinforced composite material is closely related to the anisotropy of the material. For the quantitative characterization of the anisotropy in the composite material, applied was CODF concept which was extensively used in the metallic material. As the results, the anisotropy of the material could be quantitatively analysed from the measurement of the phase velocities of the angular dependent $SH_o$ waves.

• Journal of the Korean Society for Nondestructive Testing
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• v.2 no.1
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• pp.5-9
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• 1982

Experiments were performed according to ultrasonic attenuation measurement and comparison method of DAC curve to analyze the difference between PSI and 2nd ISI ultrasonic testing results. Smaller error was found by comparison method of DAC curve, and that method was more useful practically.

• Magazine of the Korea Concrete Institute
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• v.4 no.2
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• pp.75-81
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• 1992

염분을 함유한 철근콘크리트중의 철근부식에 관한 2년 촉진시험으로부터 콘크리트표면에서 측정한 자연전위값과 실제의 철근 부식상황과를 비교한 결과 철근의 수식상황을 자연전위법을 이용하여 비파괴적으로 진단하는 방법이 유효함을 알았다. 포화칼로멜전극을 사용했을 경우 -300mV이하이면 부식이 발생하였으며 -200mV이상이면 부식이 발생하지 않았다. 또한 부시공시체에 대한 휨강도시험도 행하였으며 중성화에 대한 검토로 행하였다.

• Journal of the Korean Society for Nondestructive Testing
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• v.10 no.1
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• pp.91-95
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• 1990

Welding residual stress was measured by Barkhausen noise method. The calibration experiment was done for the quantitative analysis. The specimen for the calibration experiment must has the same thermo-mechanical history as the actual material to be tested. The Barkhausen noise were analysed by the pulse-height distribution. The results show that the distribution and magnitude of welding residual stress from Barkhausen noise method are in good agreement with those from blind hole method.

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.1
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• pp.61-67
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• 2015

Recently, the initiation of outside diameter stress corrosion cracking (ODSCC) at the tube support plate region of domestic steam generators (SG) with Alloy600 HTMA tubes has been increasing. As a result, SGs with Alloy600 HTMA tubes must be replaced early or are scheduled to be replaced prior to their designed lifetime. ODSCC is one of the biggest threats to the integrity of SG tubes. Therefore, the accurate evaluation of tube integrity to determine ODSCC is needed. Eddy current testing (ECT) is conducted periodically, and its results could be input as parameters for evaluating the integrity of SG tubes. The reliability of an ECT inspection system depends on the performance of the inspection technique and abilty of the analyst. The detection probability and ECT sizing error of degradation are considered to be the performance indices of a nondestructive evaluation (NDE) system. This paper introduces an optimized evaluation method for ECT, as well as the sizing error, including the analyst performance. This study was based on the results of a round robin program in which 10 inspection analysts from 5 different companies participated. The analysis of ECT sizing results was performed using a linear regression model relating the true defect size data to the measured ECT size data.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.4
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• pp.48-56
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• 2022

Controlling the setting time of cementitious materials is one of the most important factors in securing early-age performance of concrete structures. Recently, the use of retarding admixtures, which enable the inhibition of some hydration products to control the securing time due to average temperature rise is suggested. Although various non-destructive evaluation methods have been proposed to evaluate cement hydration and hardening of cement-based materials to overcome the limitations of Vicat needle test, experimental research is still required to use the non-destructive evaluation method with added retarding admixtures. In this study, measurements of electrical resistivity and ultrasonic wave velocity in early-aged cement pastes were performed according to the addition of retarding admixture(tartaric acid). The setting time of the cement pastes was evaluated by obtained rising time of the both non-destructive measurements. As a result, the possibility of evaluating the setting delay in cement pastes was confirmed through comparative analysis with the initial and final setting times by Vicat test. In addition, X-ray diffraction results at the rising time of electrical resistivity showed a key hydration product affecting the setting delay.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.3
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• pp.240-245
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• 2004

Torsional characteristics of nonuniform circular waveguides were studied experimentally by using an in-plane laser vibrometer. The circumferential displacement along the axis of a rod was measured as a response of the torsional oscillation excited at one end of the rod. The experimental results obtained for a stepped circular rod and a conically-tapered rod were compared with theoretical predictions. The results of this paper show the possibility of using the in-plane laser vibrometer for the measurement of torsional vibrations.

• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.4
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• pp.231-238
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• 2006

Nondestructive examination for low pressure turbine disc in standard nuclear power plant using phased array technique was studied. For this purpose, disc mockups were made and notches were machined in the mockups. Detection and length sizing by different methods are compared. Depth of deep notches could be measured by using AATT(absolute arrival time technique) or RATT(relative arrival time technique) but shallow notches that must be detected in early stage couldn't be measured by these two methods. For this case, notch depth was estimated by using signal response angle range and preyed usefulness.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.4
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• pp.294-303
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• 2005

This paper describes the analysis results of a series f Round-Robin test that was performed to intercompare inspection and diagnosis techniques for characterization of pressure tube f a pressurized heavy water reactor under the Coordinated Research Project(CRP) of IAEA's nuclear Power Programme. For this test, six nations, Korea, Canada, India, Argentina, Rumania, and China that currently have pressurized heavy water reactors under operation involved, and the "KOR-1" pressure tube sample prepared by Korea was used. Two kinds of NDE technique, ultrasonic and eddy current test, were applied for these tests. The "KOR-1" pressure tube sample contains total 12 artificial flaws such as crack-like EDM notches, wear that is similar to the real flaws and can be produced on the pressure tubes during plant operation. Test results showed that seven laboratories from six nations detected all twelve flaws in "KOR-1" specimen by using ultrasonic and eddy current test methods, and ultrasonic test method was more accurate than eddy current test method in flaw detectin and sizing. ID flaws in pressure tube sample were more easily detected and accurately sized than OD flaws.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.4
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• pp.393-401
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• 2002

Pipelines in power plants, nuclear facilities and chemical industries are often affected by corrosion effects. It is important to inspect the internal defects in pipelines in oder to guarantee safe operational condition. We have taken relatively much time, cost and manpower to use conventional NDT methods because these methods are contact measuring methods. In this paper, we used digital shearography, a laser-based optical method which allows full-field measurement of surface displacement derivatives. This method has many advantages in practical use, such as low sensitivity to environmental noise, simple optical configuration and real time measurement. The experiment was performed with pressure vessels which has different internal cracks and detected internal cracks in the pressure vessels at a real time using phase shifting method.