• 비파괴검사학회지
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• 제15권4호
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• pp.511-519
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• 1996

Cr-Mo강인 SNCM220, SCM435, SACM645 및 SCM415 강봉을 사용하여 ${\phi}31.2$ 봉 대 봉 동종재 마찰용접의 최적 조건을 실험적으로 구하였으며, 이를 위하여 이음부의 인장강도와 마찰용접 변수와의 정량적 상관식을 실험적으로 도출하였다. 한편 마찰용접시 음향방출시험을 병행하여, AE 누적총량과 마찰용접변수, 마찰용접부의 인장강도와 AE 누적총량과의 정량적 상관성을 도출하였다. 그리고, 마찰용접부의 인장파단면을 검토함으로써 용접품질을 확인하였다.

• 대한인간공학회지
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• 제18권3호
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• pp.87-103
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• 1999

The present study employed an experimental usability testing technique to explore cognitive engineering characteristics of WWW. Based on the results of our previous study which employed non-experimental methods such as questionnaire and heuristic evaluation method, this study used a behavioral performance-measurement technique to evaluate the usability of a domestic web-site design. Specifically, we revised the menu and document structure of the original 'Movie-Friend' site to solve the design problems which were extracted from the results of the heuristic evaluation method of our previous study. Exp. 1 compared the relative navigation efficiency of the original frame menu site and the revised pop-up toolbar site, and Exp. 2 compared the toolbar menu site and the revised frame site. As a result of Exp. 1, the revised pop-up toolbar site showed improved navigation efficiency compared to the original site, as indicated by the mean latency and the number of pathways to reach the target page. However, we found no performance difference between the frame site and toolbar site in Exp. 2.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 추계학술대회 논문집(I)
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• pp.187-191
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• 2003

Aluminum carbody for rolling stocks is light and perfectly recycled, but includes severe defects which are very dangerous to fatigue strength. Static load test has been performed up to date to assess structural safety of the carbody. However, static load test is not sufficient to evaluate fatigue strength of the carbody, because fatigue failure is caused by dynamic load. In this study, the established load test methods for carbody are described and the characteristics of the methods are discussed. Also, a testing method to simulate dynamic loading condition is proposed for evaluation of fatigue strength of the carbody The results by the proposed testing method are compared with the results by the static load test and new findings are discussed.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 춘계학술대회 논문집
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• pp.768-773
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• 2003

The inspection of track irregularity, which is the most important index for the evaluation of the dynamic safety of the rolling stock, is performed by setting up the testing train set. The self-diagnosis for the various rolling stocks and railways can be obtained if it is possible to take the simultaneous inspection of track irregularity for the commercial vehicle while it is running and to build up a dynamic safety evaluation system. It is expected to have some good effects, such as preventing accident with the low dynamic safety, cutting cost for the testing train set and evaluating the exact influence on the rolling stock and railway. In this study, innertial measuring method, which allows us to directly measure the track irregularity from the commercial vehicle, will be considered and some overseas cases will be explored as well.

• 한국철도학회논문집
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• 제7권1호
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• pp.32-36
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• 2004

Aluminum carbody for rolling stocks is light and perfectly recycled, but includes severe defects which are very dangerous to fatigue strength. Static load test has been performed up to date to assess structural safety of the carbody. However, static load test is not sufficient to evaluate fatigue strength of the carbody, because fatigue failure is caused by dynamic load. In this study, the established load test methods for carbody are described and the characteristics of the methods are discussed. Also, a testing method to simulate dynamic loading condition is proposed for evaluation of fatigue strength of the carbody. The results by the proposed testing method are compared with the results by the static load test and new findings are discussed.

• 한국신뢰성학회지:신뢰성응용연구
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• 제17권3호
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• pp.236-245
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• 2017

Purpose: There is no established inspection system for composite wind blade during the fabrication stage even though the blades are one of the most important part at wind generation system, but phased array ultrasonic testing method has been continuously studied about wind turbine blade with composite. When wind turbine blade with complex shape by phased array probe is inspected, it is necessary to study for system keeping constant pressure using pressure device. Methods: In this paper, we propose constant pressure device for inspecting wind turbine blade by phased array ultrasonic test method. Design of the device controller is based on Hunt-Crossley model. We evaluate reliability of phased array ultrasonic inspection result that applicated constant pressure device. Result: Defect indication is precise and its error is small when constant pressure mechanism based on Hunt-Crossley model was used. Conclusion: When inspection is progressed using constant pressure mechanism, the reliability of composite wind blade inspection can be improved.

• 한국안전학회지
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• 제33권6호
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• pp.58-65
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• 2018

The life span of the porcelain insulator was made to be 30 years, but currently many of the 154kV NGK porcelain insulators using in Korea are found to have passed the production life. Accidents caused by aged mechanical breakdown can lead to disruption of power supply in some areas, large economic losses, and casualties. Therefore, ultrasonic method, which is one of the non - destructive test methods, is applied as a method for evaluating the integrity of porcelain insulators. In this study, the experiment on the interface of cap was conducted and the difference between the energy difference and the attenuation coefficient of the reflected wave was derived according to the interface state of the steel - cement. The results of this study are expected to be used as the basic data of the ultrasonic testing to evaluate the interface condition of the porcelain insulator cap.

• 콘크리트학회논문집
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• 제11권4호
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• pp.157-167
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• 1999

Among several non-destructive testing methods, ultrasonic pulse velocity method and rebound index method have been widely used for the evaluation of concrete strength. However, such methods might not provide accurate estimated results since factors influencing the relationship between strength and either ultrasonic pulse velocity or rebound index are not considered. In this paper, the evaluation method of concrete strength using rod-wave velocity measured by impact-resonance method is proposed. A basic equation is obtained by the linear regression of velocity vs, strength data at specific age and then, aging factor is employed in the equation to consider the difference of the increasing rate between wave velocity and strength. Strengths predicted by the proposed equation agree well with test results. Furthermore, the combined method of rod-wave velocity and rebound index is proposed.

• 비파괴검사학회지
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• 제11권2호
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• pp.42-47
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• 1991

Nondestructive evaluation study was made on creep damage materials by ultrasonic spectrum analysis. The evaluation methods was developed in order to predict the change of ultrasonic attenuation with increasing creep damage. A new algorithm for the improvement of measuring accuracy of ultrasonic attenuation using a spectrum analysis has been developed. Normally, the ultrasonic attenuation is evaluated from 1st and 2nd peak values of the pulse-echo ultrasonic wave. The algorithm developed is incorporated in a measuring system which consists of a personal computer with ultrasonic apparatus and a digital storage oscilloscope. By the spectrum analysis method, it become popssible to describe approximately the attenuation change with increassing creep damage in Cr-Mo-V forging.

• 제어로봇시스템학회논문지
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• 제11권7호
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• pp.595-601
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• 2005

A mobile robot system utilizing NDT (Non-Destructive Testing) method is designed and fabricated f3r automatic integrity evaluation of large sized industrial reservoirs and pipelines. The developed mobile robot can crawl over the outer surface of the industrial facilities even though the shape of the structures is various and unsymmetric. The robot detects defects such as pinholes, cracks and thickness reduction at the wall of the facilities using EMAT (Electro-Magnetic Acoustic Transducer). Image processing technology for weld line detection at the surface of the target and host programs including defect detecting algorithms are also developed. Automation of defect detection for these kinds of large facilities using mobile robots is helpful to prevent significant troubles of the structures without danger of human beings under harmful environment.