• 한국군사과학기술학회지
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• 제18권1호
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• pp.8-14
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• 2015

Transmission of a tracked vehicle designed for multiple functions such as steering, gear-shifting, and braking is a core component of heavy vehicle to which the power is transferred based on combined technology of various gears, bearing, and fluid machineries. Robustness and durability of transmission, however, have been issued due to a large number of driving units and sub-components inside its body. Particularly, transmission housing is important structure which supports the transmission, and is made of aluminum alloy. Thus, structural robustness against such mechanical loading or vibration must be attained. Structural reliability evaluation through FEM analysis can save time and cost of the actual tests. In this study, structural evaluation is conducted on output housing of transmission, which is core component of tracked vehicle, using the simulation program. In addition, transmission dynamo test is performed to evaluate structural robustness of the output housing against the vibration which can be produced during the transmission operation.

• 한국압력기기공학회 논문집
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• 제17권1호
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• pp.36-48
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• 2021

As the material aging of nuclear power plants has been progressing in domestic and overseas, crack growth becomes one of the most important issues. In this respect, the crack growth assessment has been considered an essential part of structural integrity. The crack growth assessment for nuclear power plants has been generally performed based on ASME B&PV Code, Sec. XI but the idealization of crack shape and the conservative solutions of stress intensity factor (SIF) are used. Although finite element analysis (FEA) based on iterative crack growth analysis is considered as an alternative method to simulate crack growth, there are yet no guidelines to model the crack-tip spider-web mesh for such analysis. In this study, effects of various meshing factors on FE SIF calculation are systematically examined. Based on FEA results, proper criteria for spider-web mesh in crack-tip are suggested. The validation of SIF calculation method through mapping initial stress field is investigated to consider initial residual stress on crack growth. The iterative crack-tip modeling program to simulate crack growth is developed using the proposed criteria for spider-web mesh design. The SIF results from the developed program are validated by comparing with those from technical reports of other institutes.

• 한국압력기기공학회 논문집
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• 제6권1호
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• pp.9-15
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• 2010

This paper describes the Visual Tool for automatic ultrasonic examination that is under developing as a part of the project for development of automatic ultrasonic wave acquisition and analysis program. This tool that is supported by various image processing techniques will be adopted to detect the flaws in the component and piping welds in NPP. Visual Tool will enhance the integrity of nuclear power plant. The object of this paper is to address the Visual Tool which is developing for automatic ultrasonic inspection of welds in NPP.

• 비파괴검사학회지
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• 제13권1호
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• pp.40-45
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• 1993

The steam generator tubes of the nuclear power plant should be inspected using eddy current techniques. Recently the crack-like defects become a major concern for the integrity of the steam generator tubes. These defects could be detected by the MRPC(Motorized Rotating Pancake Coil) method, not by the conventional bobbin coil method. In this paper it has been attempted to estimate the length of the cracks at the tube expansion region using of MRPC technique. The lengths of both axial and circumferential cracks show a tendency of overestimation compared to the real lengths. As the depths of the defects decrease from 100% through 50% of the wall thickness, the error of the length estimation is increased.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.57-61
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• 2002

In this paper, the structural and thermal integrity of a Dual Mass Flywheel (DMFW) being developed by HMC is assessed with conventional FEM code. Some parts were modified in order to satisfy the SAE and RICARDO's assessment limit, and we found that FEM was valuable tools in developing new DMFW system.

• 전산구조공학
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• 제9권1호
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• pp.47-54
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• 1996

원자로 내부구조물을 구성하고 있는 중요한 구조물 중의 하나인 제어봉집합체 보호구조물에 대한 랜덤진동의 응답을 구하였다. 제어봉집합체 보호구조물은 본래의 설계로부터 많은 설계변동이 있었고 이에 대하여 많은 우려가 제기되었던 바 본 논문에서는 정상상태에서의 랜덤하중에 대한 동적해석을 수행하여 그 응답을 구하였고 이들을 실험치와 비교, 검토하였으며 제어봉집합체 보호구조물이 구조적으로 안전함을 보였다.

• 한국해양공학회지
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• 제16권5호
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• pp.66-72
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• 2002

Fracture behaviors of pipes with local wall thinning are very important for the integrity of nuclear power plant. However, effects of local wall thinning on strength and fracture behaviors of piping system were not well studied. Acoustic emission(AE) has been widely used in various fields because of its extreme sensitivity, dynamic detection ability and location of growing defects. In this study, we investigated failure modes of locally wall thinned pipes and AE signals by bending test. From test results, we could be divided four types of failure modes of ovalization, crack initiation after ovalization, local buckling and crack initiation after local buckling. And fracture behaviors such as elastic region, yielding region, plastic deformation region and crack progress region could be evaluated by AE counts, accumulative counts and time-frequency analysis during bending test. The result of the frequency range is expected to be basic data that can inspect plants in real-time.

• Nuclear Engineering and Technology
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• 제48권3호
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• pp.831-839
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• 2016

Seismic qualification by test is widely used as a way to show the integrity and functionality of equipment that is related to the overall safety of nuclear power plants. Another means of seismic qualification is by direct integration analysis. Both approaches require a series of time histories as an input. However, in most cases, the possibility of using real earthquake data is limited. Thus, artificial time histories are widely used instead. In many cases, however, response spectra are given. Thus, most of the artificial time histories are generated from the given response spectra. Obtaining the response spectrum from a given time history is straightforward. However, the procedure for generating artificial time histories from a given response spectrum is difficult and complex to understand. Thus, this paper presents a simple time-domain method for generating a time history from a given response spectrum; the method was shown to satisfy conditions derived from nuclear regulatory guidance.

• 한국소음진동공학회논문집
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• 제26권5호
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• pp.594-601
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• 2016

Mass estimation analysis of loose-parts in pressure vessel is necessary for the structural integrity assessment of pressure boundary in nuclear power plants. Mass of loose-parts can be generally estimated from the peak values and the center frequency of impact signals. Magnitude of impact signals is, however, inevitably attenuated according to the traveling distance of the signals and depending on the frequencies. Attenuation rate must be therefore carefully compensated for the precise estimation of loose-part mass. This paper proposes a new compensation method for the attenuation rate based on Bessel function instead of Hankel function in conventional method which has a limitation of usage in near the impact location. It was verified that the suggested compensating equation based on the Bessel function can be applied to the attenuation rate calculation without any limitation.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.351-356
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• 2001

A potential loss of structural integrity due to aging of nuclear piping may have a significant effect on the safety of nuclear power plants. In particular, failures due to the erosion and corrosion defects are a major concern. As a result, there is a need to assess the remaining strength of pipe with erosion/corrosion defects. In this paper, a limit load solution for the eroded and corroded SA106 Grade B pipes subjected by internal pressure is developed. based in 3-D finite element analyses, considering a wide range of the shape of pipeline, flaw depth and axial flaw length parametrically.