• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.2
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• pp.97-104
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• 2007

An investigation has been made on the relationship between characteristics of Acoustic Emission (AE) signal in welding flaw and the stress corrosion defect in-service for the high pressure pipe steel. In order to tackle the problem of welding flaw in high pressure pipe, specimens were made by the aid of the application of both corrosion liquid usage and a quenching method after local heating. The amplitude of signal was $60{\sim}75\;dB$ in the territory which is suspected for defect, and the specimens which only have welding flaw showed gradients of 0.034, 0.034, 0.035. Moreover, there is a certain increase in gradient even though the differences are very slight. That is, corrosion specimens showed new gradients of 0.040, 0.039, 0.041 which put welding flaw and corrosion mechanism together. After pressurizing 3 minutes, AE signal has been detected from welding flaw easily in each part of the section. It is possible to predict the occurrence and also prevent the damage of stress corrosion crack which has characteristics of cleavage fracture.

• The Journal of Engineering Geology
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• v.5 no.1
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• pp.31-44
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• 1995

The puppose of this study is to propose the numerical modelling criteria for underground opening, rock mass continuum is regarded as homogeneous rock behaved linear elastic. The results of this study are summarized as follows: - Boundaries of the finite element mesh should be located at least 6 radii away from the center of the opening. - For circular openings, tension only developed when $K_0$ was less than one-fourAs the ratio of initial horiwntal to vertical stress increased, the inward springline movement increased and the inward crown movement decreased. - The displacement patterns developing for opening I shaped horse-shoe and opening II shaped powerstation are similar to those for circular openings. For both type opening I and opening II, stress concentrations develop at the intersection of the wall and floor. Greater stress concentrations are found for the type opening II.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.2
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• pp.40-48
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• 2016

To observe the rail-slab interaction in continuous welded railway(CWR) bridge when earthquake occurs, additional axial rail stresses and relative longitudinal displacements between rail and bridge deck were calculated with input of various load combinations and 3 different types of seismic loads to an analytical model. As results of analysis, it can be found that standard response spectrum proposed by Korea Rail(KR) network authority for earthquake design showed less additional axial rail stresses than allowable levels, but greater relative longitudinal displacement between rail and bridge deck, which means that adjustment of relative longitudinal displacement within a standard level is much more difficult than axial train stress. Additionally, if a large-scaled earthquake as occurred at Kobe, Japan comes up, then both of additional axial rail stress and relative displacement in rail-bridge deck may exceed allowable levels, which indicates to make proper design guides against sudden earthquake occurrence.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4A
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• pp.677-687
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• 2006

Kriging interpolation is one of the generally used interpolation techniques in Geostatistics field. This technique includes the experimental and theoretical variograms and the formulation of kriging interpolation. In contrast to the conventional least square method for stress recovery, kriging interpolation is based on the weighted least square method to obtain the estimated exact solution from the stress data at the Gauss points. The weight factor is determined by variogram modeling for interpolation of stress data apart from the conventional interpolation methods that use an equal weight factor. In addition to this, the p-level is increased non-uniformly or selectively through a posteriori error estimation based on SPR (superconvergent patch recovery) technique, proposed by Zienkiewicz and Zhu, by auto mesh p-refinement. The cut-out plate problem under tension has been tested to validate this approach. It also provides validity of kriging interpolation through comparing to existing least square method.

• Land and Housing Review
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• v.2 no.2
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• pp.163-170
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• 2011

Individual Vacuum Pressure Method (IVPM) is a soft ground improvement technique, in which a vacuum pressure can be directly applied to the vertical drain board to promote consolidation and to strengthen the soft ground. This method does not require surcharge loads, different to embankment or pre-loading method. In this study, the ground improvement efficiency of Individual Vacuum Pressure Method was estimated when suction pressure increases step by step(-20, -40, -60, -80kPa) with different periods. During Individual Vacuum Pressure Method process, surface settlement and pore pressure were monitored, and cone resistance as well as water content were also measured after the completion of Individual Vacuum Pressure Method treatment. From the results, optimum duration of each step of vacuum pressure was determined, and the settlement was calculated using FEM numerical analysis.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.1
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• pp.26-33
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• 2014

In this study, Non-load-carrying EH Grade steels in fillet welded joints were evaluated with both the hot spot stress method and the 1mm stress method. The thickness effect criterion for fatigue strength evaluation of welded of welded steel structures recommendations of the IIW was used to evaluate the fatigue strength of EH40 and EH36 and Both EH40 and EH36 have been compared with FAT 125 curve recommended in the IIW. Furthermore, fatigue strength of the welded tow and the ground conditions for Non-load-carrying EH36 based on the 1mm stress method has been discussed.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.10a
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• pp.116-123
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• 2000

본 논문은 1995년 일본 남부 효고켄 남부 지진 (코베 대지진)에 의해 코베시에 위치하는 인공섬인 포트 아일랜등서 발생한 액상화 현상을 해석적 기법을 동원하여 액상화 현상의 저감 효과 혹은 방지를 위하여 실시되어져 오고 있는 여러 공법들의 타당성을 수치해석적인 입장에서 검증한 것이다. 따라서, 본 논문에서는 코베시에 의해 획득되어진 연직 방향의 지진 기록에 의해 포트 아일랜드 시공 당시 구역별로 다른 지반 개량 공법을 실시했고, 혹은 실시하지 않는 구역에 대해서 1차원 및 2차원 전응력 그리고 유효 응력 해석 기법을 동원하여 일련의 해석을 실시하였고 그 결과를 다각적인 방향에서 제시하였다.

• The Journal of Engineering Geology
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• v.6 no.1
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• pp.45-49
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• 1996

It is shown that the concept of 'earthquake quanta' proposed by Sacks and Rydeleck (1995) may be expressed in a more general form. The property that for large earthquakes the stress drop is approximately a constant, while for small events the stress drop is proportional to the moment seems independent of the failure criteria of the earthquake quanta. The physical significance of the concept of earthquake quanta is discussed in the perspective of 'seismon'.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.557-561
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• 2004

The hot gas casing of gas turbine has operated high temperature and thermal gradient. The structure safety of hot gas casing will be highly depend on the thermal stress. In this paper, flow and thermal stress analysis of hot gas casing is carried out using ANSYS program. The obtained temperature data by flow analysis of hot gas casing apply the load condition of the thermal analysis. The thermal stress analysis is carry out the elastic-plasticity analysis. The pressure, temperature and velocity of the flow and thermal stress of the hot gas casing are presented.

• Journal of Auto-vehicle Safety Association
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• v.4 no.1
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• pp.23-26
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• 2012

본 논문은 듀얼클러치 변속기 변속 메커니즘 개발을 위한 동역학적 시뮬레이션 해석 및 피로수명 해석에 관한 연구이다. 캠을 이용한 쉬프트 포크의 이송으로 기어를 변속하는 개념을 갖는 쉬프트 메커니즘의 작동성 및 설계안 검증을 위해 캠의 회전 속도, 접촉면의 경계조건 및 싱크로나이저 슬리브에서의 저항을 반영한 모델링을 구성하여 동역학적 시뮬레이션을 실시하였다. 각 파트의 응력 및 변형률 발생을 해석하여 설계 개선안을 도출하고, 개선안이 반영된 최종 시작모델의 시뮬레이션 상 최대 응력 발생 시점에서 시프트 포크의 각 접촉면 별 외력 작용을 분석하여 이를 적용한 피로 해석을 진행하였다.