• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.2
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• pp.151-157
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• 2004

Ultrasonic testing is a kind of nondestructive test to detect a crack or discontinuity in materials or on material surfaces by sending ultrasound to it. This conventional ultrasonic technique has some limitations in reliably detecting crack or accurately assessing materials in the case of complex-shaped power plant components such as a turbine blade root. An alternative method for such a difficult inspection is highly needed. In this study, application of a phased array ultrasonic testing (UT) system to a turbine blade, one of the critical power plant components, has been considered, and the particular incident angle has been determined so that the greatest track detectability and the most accurate crack length evaluation nay be achieved. The response of ultrasonic phased array was also analyzed to establish a special method to determine the track )ength without moving the transducer. The result showed that the developed method for crack length assessment is a more accurate and effective method, compared with the conventional method.

• International Journal of Highway Engineering
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• v.16 no.5
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• pp.1-8
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• 2014

PURPOSES : The objective of this study is to evaluate the bond strength of asphalt emulsions including polymer-modified emulsions for chip seals and fog seals using the bitumen bond strength (BBS) test. METHODS : For the laboratory testing, the Pneumatic Adhesion tensile Testing Instrument(PATTI) device is used to measure the bond strength between the asphalt emulsion and aggregate substrate based on the AASHTO TP-91. In order to conduct all the tests in controled condition, all test procedures are performed in the environmental chamber. The CRS-2L and the SBS CRS-2P emulsions are used as a polymer-modified emulsion, and then unmodified emulsion, the CRS-2, is compared for the evaluation of chip seal performance. For the fog seal performance evaluation, two types of polymer-modified emulsions and one of unmodified emulsion, the CSS-1H, are employed. For chip seal study, the BBS tests are performed at 30, 60, 120, and 240 minutes of curing times with curing and testing temperatures of $15^{\circ}C$, $25^{\circ}C$, and $35^{\circ}C$. The fog seal tests are conducted at 30, 60, 90, 120, 180 minutes, and 24 hours with curing and testing temperatures of $25^{\circ}C$, $30^{\circ}C$, and $35^{\circ}C$. RESULTS AND CONCLUSIONS : Overall, chip seal emulsions and fog seal emulsions show the similar bond strength trend. At the same testing condition, polymer-modified emulsions show better bond strength than unmodified emulsions. Also, there is no significant difference between polymer-modified emulsions. One of important findings is that the most bond strength reaches their final bond strength within one hour of curing time. Therefore, the early curing time plays a vital role in the performance of chip seals and fog seals.

• Journal of the Korean Society of Safety
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• v.34 no.5
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• pp.31-36
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• 2019

This study made a testing device to evaluate the distribution board management system. Power was supplied to the testing device using a loading-back method and the voltage applied to it was 440 V at the same turn ratio. When the human body electric shock current is 30 mA, the breaking time is set to be less than 240 ms while 30~45 mA current is flowing. The test result shows that in the case of the R-phase it was measured to be 5.19 Hz (193 ms). And the S-phase and T-phase were perfectly cut off at 5.39 Hz (186 ms) and 5.71 Hz (175 ms), respectively. When the human body electric shock current is 60mA, the breaking time is set to be less than 120 ms while 45~75 mA current is flowing. The test result shows that the R-phase, S-phase, and T-phase were accurately cut off at 8.39 Hz (11 ms), 8.87Hz (113 ms) and 9.69 Hz (103 ms), respectively. When the human body electric shock current is 90 mA, the breaking time is set to be less than 48 ms while 75 mA current is flowing. The test result shows that the R-phase, S-phase, and T-phase were accurately cut off at 19.8 Hz (50.4 ms), 16.9 Hz (59.2 ms), and 17.9 Hz (56.0 ms), respectively. That is, the developed testing device satisfied all the requirements of the distribution board evaluation criteria, and it becomes available for the performance evaluation of the distribution board management system.

• Journal of the Korean Institute of Intelligent Systems
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• v.25 no.6
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• pp.542-550
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• 2015

Usually, a new SSD (Solide State Drive) product is developed based on the software platform of the previous product. Therefore, when using the same test case was used to evaluate the previous generation evaluation of new products are a number of advantages may be, but a priority or weight is the inefficiency exists in the use of the evaluation resources due to not considered. A new method is proposed to prevent the waste of testing resources. Through the analysis of the evaluation data for the previous products, the combinations of testing cases with the highest probability for defect detections are identified. When the software is to be reused, most part of the base software platform is rarely modified and only some modules are added or modified. So, the whole software system may have similar types of defects with the previous products. By utilizing the evaluation data for the previous proucts, we can detect defects at an early stage.

• Journal of the Korea Institute of Building Construction
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• v.23 no.1
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• pp.45-56
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• 2023

This study was conducted to examine the feasibility of preparing a durability evaluation plan in watertightness for sealant applied to a PC structure. To this end, 5 types of sealant that equally satisfy the quality standards of the relevant KS standard were selected and tested. Through this testing, it was found that 3 of the 5 types of sealant showed deterioration in watertightness and durability, such as falling off and cracking from the substrate. For the remaining two types, a visual observation showed no significant changes, but additional analysis, confirmed that there was a large difference in the stress reduction rate of the material. Therefore, based on the above results, the need for a performance review in durability between sealant was confirmed, and based on this, the validity of the durability evaluation plan that can be used in product selection was quantitatively confirmed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.860-864
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• 2004

This article discusses the use of pulse-echo ultrasonic testing for the stress analysis of adhesive bonds between metal sheets. The method is based on the measurement of the reflection wave at the metal/adhesive interface. After describing briefly the physical aspects of the phenomenon, an index is defined to detect defective zone of the joint(both for the lack of adhesive and for insufficient adhesion); the influence of the experimental variables(variables stress...) on the measurement is discussed. By means of a control experiment it is shown that Stress Variation in Adhesive Joints are separate to be distingguished. In this paper, Quantitative Nondestructive Evaluation in Adhesive Joints are together with Ultrasonic Testing and Finite Element Method.

• Journal of the Korean Society for Nondestructive Testing
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• v.9 no.2
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• pp.18-24
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• 1989

Computer-aided high frequency ultrasonic is applied to aluminum oxide(85w%, 94w%, 96w%, and 99w%) MOR(modulus of rupture) samples to evaluate mechanical properties such as density variation, pore content, elastic modulus, shear modulus, and poisson's ratio. Ultrasonic wave velocity and attenuation measurement techniques were used as an evaluator of such properties. Pulse-echo C-Scan images with different fate setting method using 50MHz center frequency 1 inch focal length transducer allows evaluation of density variation and pore content. Elastic modulus calculated with the relation of density and ultrasonic velocity. It shows good reliability as compared with resonance method. Sintered density variation of $0.025g/cm^{3}$, that is 0.6% of theoretical density in $Al_{2}O_{3}$ samples can be observed by ultrasonic velocity measurement. Attenuation measurement method qualitatively agree with 4-point fracture testing result concerning of porosity content.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.3
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• pp.157-162
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• 2005

In order to evaluate the corrosion of reinforcing steel-bars (rebar) in concrete, a nondestructive evaluation by the half-cell potential method is currently applied. In this study, potentials measured on a concrete surface are compensated into those on the concrete-rebar interface by the inverse boundary element method (IBEM). Because these potentials are obtained three-dimensionally (3-D), 3-D visualization is desirable. To this end, a visualization system has been developed by using VRML (Virtual Reality Modeling Language). As an application, results of a reinforced concrete (RC) slab with corroded rebars are visualized and discussed.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.334-341
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• 2002

Nowadays, owing to the development of analysis techniques for PDA test, we can evaluate the serious damage of pile during driving in site. In this study, we checked the damage of pile by pulling it out after evaluation of the pile damage during driving by PDA testing. After that, almost damaged pile was checked and the outline depth of damage could be verified. To increase the quality of driven pile, we have to increase the number of PDA testing for drivability analysis with checking the damage especially for preliminary pile driving and dynamic load test for checking the bearing capacity and consider the application of driving by energy monitoring.

• Journal of the Korea Society of Computer and Information
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• v.24 no.4
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• pp.107-112
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• 2019

Failure testing is a test that verifies that the system is operating in accordance with failure response requirements. A typical failure test approaches the operating system by identifying and testing system problems caused by unexpected errors during the operational phase. In this paper, we study how to evaluate these Failure at the software development stage. Evaluate the probability of failure due to code changes through the complexity and duplication of the code, and evaluate the probability of failure due to exceptional situations with bugs and test coverage extracted from static analysis. This paper studies the possibility of failure based on the code quality of software development stage.