• 대한조선학회논문집
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• 제53권6호
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• pp.514-520
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• 2016

Oil and gas production riser systems need to be designed considering a wide band quarter-modal analysis which contains low-, wave-, VIV(Vortex induced vibration) frequencies. The VIV can be separated into cross-flow(CF) and in-line(IL) components. In this study, the various idealized tri- and quarter-modal spectra are suggested to analyze fatigue damage on the production riser system. In order to evaluate the fatigue damage increment caused by the IL's motion, tri- and quarter-modal spectral fatigue damages are calculated in time domain. And the fatigue damage calculated from two different modal spectra are compared quantitatively. Then the suitability of existent wide band fatigue damage models for quarter modal spectrum was evaluated by comparison of frequency domain calculation and time domain calculation. The result show that although spectral density of IL motion is not remarkable in quantity, the effect on the fatigue damage is significant and existent fatigue damage models are not adequately estimating damage by quarter-modal spectra.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2000년도 춘계학술대회 발표논문집
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• pp.213-222
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• 2000

In present study, a stochastic model is developed for the low cycle fatigue life prediction and reliability assessment of 316L stainless steel under variable multiaxial loading. In the proposed model, fatigue phenomenon is considered as a Markov process, and damage vector and reliability are defined on every plane. Any low cycle fatigue damage evaluating method can be included in the proposed model. The model enables calculation of statistical reliability and crack initiation direction under variable multiaxial loading, which are generally not available. In present study, a critical plane method proposed by Kandil et al., maximum tensile strain range, and von Mises equivalent strain range are used to calculate fatigue damage. When the critical plane method is chosen, the effect of multiple critical planes is also included in the proposed model. Maximum tensile strain and von Mises strain methods are used for the demonstration of the generality of the proposed model. The material properties and the stochastic model parameters are obtained from uniaxial tests only. The stochastic model made of the parameters obtained from the uniaxial tests is applied to the life prediction and reliability assessment of 316L stainless steel under variable multiaxial loading. The predicted results show good accordance with experimental results.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.905-910
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• 2003

In this paper, we develop real-time monitoring system to detect third-party damage on natural gas pipeline by using sound propagation model. Since many third-party incidents cause damage that does not lead to immediate rupture but can grow with time, the developed real-time monitoring system can execute a significant role in reducing many third-party damage incidents. The developed system is composed of three steps as follows: i) DSP based system, ii) wireless communication system, iii) the calculation and monitoring software to detect the position of third-party damage using the propagation speed of acoustic wave. Furthermore, the developed system was set at practical offshore pipeline between two islands in Korea and it has been operating in real time.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1992년도 춘계학술대회 논문집
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• pp.306-312
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• 1992

The prevention of roll breakage in hot rolling process is improtant to reduce maintenance cost and production loss. Rolling conditions such as the roll force and torque have been intensively studied to overcome the roll breakage. in the present work, a model for life prediction of work rolls under working condition was developed and discussed. The model consists of stress analysis, crack propagation, wear and fatigue calculation model. Roll life can be predicted by stress, crack depth and fatigue damage calculated from this model. The reliability of stress analysis is backed up by the FEM analysis. From the result of simulation using by pressent model, although the fatigue damage of back up roll reachs 80% of practical limit, that of workroll was less than 40%. In edge section of workroll stress amplification is found by wear and bender effect. We can judge that workroll failures are not due to fatigue damage, crack propagation by bending stress but stress amplification by wear and bender in present working condition.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2006년도 학술발표회 논문집
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• pp.374-381
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• 2006

This study presents a new information model for building a database which is used for the Damage Calculation in a Road network after Seismic outbreak (DCRS). The component which is required for information system and data analysis is divided by four factors. Those are Ground Motion Component, Road Network Component, Fragile Structure Component, and Cost Component. These components have various manners and procedures that build informations by each systems. In this study, applying the domestic system resources and these four factors, we presented the integrated evaluating system. finally, we also present the prototype of DCRS based on the ArcGIS. It is expected that developed prototype can play a role in more improved DCRS by advanced study.

• Wind and Structures
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• 제38권6호
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• pp.445-459
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• 2024

To model the aeroelasticity in vortex-induced vibrations (VIV) of slender tubular towers, this paper presents an approach where the aerodynamic damping distribution along the height of the structure is calculated not only as a function of the normalized lateral oscillation but also considering the local incoming wind velocity ratio to the critical velocity (velocity ratio). The three-dimensionality of aerodynamic damping depending on the tower's displacement and the velocity ratio has been observed in recent studies. A contour map model of aerodynamic damping is generated based on the forced vibration tests. A sectional calculation procedure based on the spectral method is developed by defining the aerodynamic damping locally at each increment of height. The proposed contour map model of aerodynamic damping and the sectional calculation procedure are validated with full-scale measurement data sets of a rotorless wind turbine tower, where good agreement between the prediction and measured values is obtained. The prediction of cross-wind response of the wind turbine tower is performed over a range of wind speeds which allows the estimation of resulting fatigue damage. The proposed model gives more realistic prediction in comparison to the approach included in current standards.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(2)
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• pp.637-642
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• 1996

This paper presents the analysis results for the core degradation processes and the fission product release of the PHEBUS FPT0 experiment using MELCOR1.8.3. The objective of this study is to assess models associated with the core damage and fission product behavior in MELCOR. The calculation results were much improved through sensitivity studies. Thermal/hydraulic behavior in the core and the circuit was well predicted under the intact core geometry. In non-eutectic model case. the UO$_2$ dissolution model in the MELCOR always showed such a tendency that the resulting dissolved UO$_2$ mass was small at the highly oxidized condition due to the model logic. Total H$_2$ generation mass was underpredicted because the stiffner was not modeled and the liner in the shroud was not allowed to be oxidized in MELCOR. Some difficulties were found in modeling the activation product were solved by manipulating the RN input associated with the initial fission product inventory. These problem were occurred because there are no control rod model in MELCOR. Generally the fission product release ratio showed a similar trend compared with the measured data except the activation product. which have no model to simulate in MELCOR.

• 한국측량학회지
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• 제33권6호
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• pp.507-516
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• 2015

Debris flow is a representative natural disaster in Korea and occurs frequently every year. Recently, it has caused considerable damage to property and considerable loss of life in both mountainous and urban regions. Therefore, It is necessary to estimate the scope of damage for a large area in order to predict the debris flow. A response model such as the random walk model(RWM) can be used as a useful tool instead of a physics-based numerical model. RWM is a probability model that simplifies both debris flows and sedimentation characteristics as a factor of slopes for a subjective site and represents a relatively simple calculation method compared to other debris flow behavior calculation models. Although RWM can be used to analyzing and predicting the scope of damage caused by a debris flow, input variables for terrain conditions are yet to be determined. In this study, optimal input variables were estimated using DEM generated from the Aerial Photograph and LiDAR data of Mt. Umyeon, Seoul, where a large-scale debris flow occurred in 2011. Further, the deposition volume resulting from the debris flow was predicted using the input variables for a specific area in which the deposition volume could not be calculated because of work restoration and the passage of time even though a debris flow occurred there. The accuracy of the model was verified by comparing the result of predicting the deposition volume in the debris flow with the result obtained from a debris flow behavior analysis model, Debris 2D.

• 한국시뮬레이션학회논문지
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• 제28권1호
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• pp.11-21
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• 2019

무기효과 산출을 위해 모델링 및 시뮬레이션 방법을 많이 사용하고 있다. 포병탄에 대한 무기효과 산출도 일부 진행되었으나, 장약의 선택에 따른 영향에 관한 연구는 부족하였다. 따라서 본 논문에서는 장약에 기반한 포병탄 EFD 산출모형을 제시하고, 장약의 선택에 따른 3차원 건물표적에 대한 무기효과의 차이를 확인하고자 한다. 우선 산출모형의 입력데이터를 수집하고, 제시한 모형을 이용하여 요망효과 달성을 위한 발사탄수를 산출하였다. 마지막으로 제시된 모형의 검증을 위해 대응표본 t-검정을 실시하였다.

• 대한조선학회논문집
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• 제31권1호
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• pp.14-21
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• 1994

국제해사기구(IMO)에서는 해상에서 빈번히 발생되는 선박의 사고방지를 위한 노력의 일환으로 그동안 특별한 규정이 없었던 건화물선(Dry Cargo ship)의 안정성에 관한 설계 기준을 수립하고 1992년 2월 1일부터 건화물선의 손상복원력 계산은 확률이론을 적용하여 수행하도록 하는 새로운 규정을 삽입하였다. 새로운 규정에 의하여 길이 l00m 이상의 Ro-Ro 선을 포함한 모든 건화물선에 대한 손상복원력 평가는 반드시 수행되어야 한다. 확률이론을 이용한 새로운 방법은 기존의 결정론적 방법과는 달리 계산의 복잡성, 반복성 등으로 인하여 전산 프로그램의 이용없이는 불가능하므로 프로그램 개발을 반드시 필요로 한다. 본 연구에서는 외국에서 도입되는 시스템에 대응하는 국내 자체의 전산코드 확보를 염두에 두어 새로운 규정을 해석하고 그에 따른 프로그램을 개발하였다. 특히 격자모델을 이용한 손상조합의 자동생성기법을 개발하므로써 간편한 입력체계를 실현하여 효율성과 정확성의 향상을 이루었다. 개발된 프로그램의 검증을 위하여 시험선박에 대한 예제를 수행하고 외국의 결과와 비교 분석하였다.