• Advances in Computational Design
• /
• 제7권1호
• /
• pp.57-68
• /
• 2022

A simulation study of the distribution of magnetic flux induced by a U-shaped electromagnet into a two-layer massive object with variations in the depth and properties of the surface layer has been carried out. It has been established that the hardened surface layer "pushes" the magnetic flux into the bulk of the magnetized object and the magnetic flux penetration depth monotonically increases with increasing thickness of the hardened layer. A change in the thickness and magnetic properties of the surface layer leads to a redistribution of magnetic fluxes passing between the poles of the electromagnet along with the layer and the bulk of the steel object. In this case, the change in the layer thickness significantly affects the magnitude of the tangential component of the field on the surface of the object in the interpolar space, and the change in the properties of the layer affects the magnitude of the magnetic flux in the magnetic "transducer-object" circuit. This difference in magnetic parameters can be used for selective testing of the surface hardening quality. It has been shown that the hardened layer pushes the magnetic flux into the depth of the magnetized object. The nominal depth of penetration of the flow monotonically increases with an increase in the thickness of the hardened layer.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2004년도 하계학술대회 논문집 C
• /
• pp.1888-1890
• /
• 2004

현대사회에 들어서면서, 전력수요의 중가와 전력기기산업의 고집적화에 따라 사고시에 발생하는 파급효과가 대형화되는 추세에 있다. 따라서 이를 미연에 방지하기 위한 연구가 각 분야에 걸쳐 활발하게 진행되고 있다. 이에 당사에서는 초고압 계통에서 사용되는 SF6가스 절연 GIS(Gas Insulated Switchgear) 및 Oil-Transformer에서의 부분방전 측정/분석을 위하여 UHF/AE를 이용한 on-line/portable 측정 시스템을 개발하였다. 본 논문에서는 개발/상용화 되어 field에서 사용되고 있는 시스템의 전반에 대하여 설명한다. 또한 철재 선진사와 공동 진행중인 Risk Assessment에 대하여 언급하였다.

• Journal of Information Technology Applications and Management
• /
• 제11권2호
• /
• pp.191-204
• /
• 2004

Many software reliability growth model(SRGM) have been proposed for past several decades. Most of these propositions assumed the S/W debugging testing efforts be constant or even did not consider them. A few papers were presented as the software reliability evaluation considering the testing effort was important afterwards. The testing effort forms which have been presented by this kind of papers were exponential, Rayleigh, Weibull, or Logistic functions, and one of these 4 types was used as a testing effort function depending on the S/W developing circumstances. We consider the methology to evaluate the SRGN using least square estimator(LSE) and maximum likelihood estimator(MLE) for those 4 functions, and then examine parameters applying actual data adopted from real field test of developing S/W.

• 비파괴검사학회지
• /
• 제12권4호
• /
• pp.32-39
• /
• 1993

Past, present and future of nondestructive testing and evaluation(NDT&E) activities in Korea are reviewed. The current status and future direction in NDT&E research and development are presented. The newly revised edition of Korean NDT personnel qualification system is described. Other activities such as NDT&E training programs, NDT field services, and professional societies and international cooperation are also summarized. Founded in 1980, the Korean Society for Nondestructive Testing is now the center of domestic activities in NDT&E as well as the gateway to the international cooperation.

• 비파괴검사학회지
• /
• 제13권2호
• /
• pp.94-100
• /
• 1993

이번 호부터 해설란을 통하여 비파괴검사(非破壞檢査) 기술(技術)에 대한 연재를 시작한다. 앞으로 비파괴검사(非破壞檢査) 기술(技術) 각 분야에 대해 다룰 예정이며 우선 1차적으로 와전류탐상법(渦電流探傷法)에 관해 3회에 걸쳐 게재하기로 한다. 특정한 비파괴검사(非破壞檢査)의 전문가가 아니더라도 쉽게 이해할 수 있도록 가급적 수식은 배제하고 기초적인 이론을 소개할 것이며 특히 현장 적용에 중점을 두어 기술(記述)하고자 한다. 본 원고에서는 원거리 와전류탐상법(渦電流探傷法)(remote field eddy current testing) 이나 펄스 와전류탐상법(渦電流探傷法)(pulsed eddy current testing)과 같은 특수 와전류(渦電流) 기술(技術)은 제외하였으며 본 연구실에서 내부 교육용으로 사용하는 "와전류탐상법(渦電流探傷法) Level I 과정"과 미국금속학회에서 발행한 Metal Handbook, 9th ed., Vol. 17, "Non-destructive Evaluation and Quality Control" 및 기타 관련 기술 자료들을 참고하였으나 일일이 명기하지는 않는다.

• 비파괴검사학회지
• /
• 제28권6호
• /
• pp.524-530
• /
• 2008

The spin valve tunneling magnetoresistance (SV-TMR) sensor performance is analyzed using Stoner-Wohlfarth model for the detection of eddy current signals in nondestructive testing applications. The SV-TMR response in terms of the applied AC magnetic field dominantly generates the second harmonic amplitude in hard axis direction. The second harmonic eddy current signal detection using SV-TMR sensor shows higher performance than that of the coil sensor at lower frequencies. The SV-TMR sensor with high sensitivity gives a good solution to improve the low frequency performance in comparison with the inductive coil sensors. Therefore, the low frequency eddy current techniques based on SV-TMR sensors are specially useful in the detection of hidden defects, and it can be applied to detect the deeply embedded flaws or discontinuities in the conductive materials.

• 한국자동차공학회논문집
• /
• 제11권3호
• /
• pp.209-213
• /
• 2003

It is advantage of accelerated vibration testing to compress service exposures to operating vibration into a reduced laboratory test by increasing the amplitude or frequency of the applied input excitations. This paper proposes an accelerated test method to estimate the high-cycle fatigue life under random excitation. The method consists of conducting a test with amplified input excitation and extrapolating linearly the lift in the accelerated condition into the real lift in field condition. The extrapolation is carried out applying the high-cycle irregular excitation fatigue theory including the rainflow counting, Miner’s damage accumulation rule, and Goodman’s mean stress correction. As a verification, those estimated lift is compared with that acquired by experiment f3r the simple case of spot welding specimen with good agreement. This testing procedure will provide an useful scheme that can reduce testing period associated with developing time schedule of new product.

• 대한전기학회논문지:전력기술부문A
• /
• 제48권9호
• /
• pp.1161-1166
• /
• 1999

Delay testing has become highlighted in the field of digital circuits as the speed and the density of the circuits improve greatly. However, delay faults in sequential circuits cannot be detected easily due to the existence of state registers. To overcome this difficulty a new scan filp-flop is devised which can be used for both stuck-at testing and delay testing. In addition, the new scan flip-flop can be applied to both the existing functional justification method and the newly-developed reverse functional justification method which uses scan flip-flops as storing the second test patterns rather than the first test patterns. Experimental results on ISCAS 89 benchmark circuits show that the number of testable paths can be increased by about 10% on the average.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2007년도 추계학술대회 논문집
• /
• pp.301-305
• /
• 2007

The performance of the railway bogie is classified into the stability and the steering performance. Testing for the bogie stability is conducted on the roller rig. But testing for the bogie steering performance on test facility is very difficult, so the testing for the vehicle curving performance is conducted on the real curve track. And it is desirable to test on the full scale test rig, but it caused many problems relating to test costs, test time. To overcome these problems, the small scale test rig is actively used in the field of bogie stability. Thus, in this paper, we have studied the scale track to test the bogie steering performance. For this, we designed the 1/5 scale test track equivalent to radius 200 curve and confirmed the validity of the testing for the bogie steering performance on the scale curve track through the testing using 1/5 scale bogie.

• 비파괴검사학회지
• /
• 제25권3호
• /
• pp.163-170
• /
• 2005

A modular Gaussian beam model is developed to simulate some ultrasonic testing configurations where multiple interfaces are involved. A general formulation is given in a modular matrix form to represent the Gaussian beam propagation with multiple interfaces. The ultrasonic transducer fields are modeled by a multi-Gaussian beam model which is formed by superposing 10 single Gaussian beams. The proposed model, referred to as "MMGB" (modular multi-Gaussian beam) model, is then applied to a typical contact and angle beam testing configuration to predict the output signal reflected from the corner of a vertical crack. The resulting expressions given in a modular matrix form are implemented in a personal computer using the MATLAB program. Simulation results are presented and compared with available experimental results.