• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.10 s.181
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• pp.2654-2663
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• 2000

Steam turbine rotors are the most critical and highly stressed components of a steam power plant; therefore, the life expectancy of the turbine rotor is an important consideration for the safety of a steam power plant. The objective of this paper is to develop a life estimation program for turbine rotors for all possible operating conditions. For this purpose, finite element analysis was carried out for four normal operating modes (cold, warm, hot and very hot starts) using ABAQUS codes. The results are made into databases to evaluate the life expenditure for an actual operating condition. For any other possible abnormal operating condition, the operating data are transmitted to the server (workstation) through a network to carry out finite element analysis. Damage estimation is carried out by transmitting the finite element analysis results to the personal computer, and then the life expectancy is calculated.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.6
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• pp.575-586
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• 2015

In NATM tunnel, the Ground-Lining Interaction model(GLI model) had been proposed a one of the numerical analysis as the ground load estimation method of the concrete lining. But this model was not applied with the interface mechanism between the ground and the support member or concrete lining. Therefor in this study, it is implemented as a model for closer than actual states that the interface element applied to the existing GLI model. And the modified GLI formula is proposed with the ground load estimation that is from the numerical results for each ground and rock cover conditions. Based on the numerical results, the ground load acting on concrete lining is reduced to ave. 88~106% in case of IV ground condition and ave. 47~57% in case of weathered soil condition comparing with the existing GLI model. It can be anticipated that the results obtained from this study can be applied to an estimation of the ground load on the concrete lining modeled like as real states, consistent and economical design.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1429-1433
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• 2004

Recently, a dangerous event occurred at the field industry and mechanical system. At developed by SUNGGOK corp. a R-L clutches of a small and high capacity serves safety device from a variety environment of mechanical system, it permits transmission of driving torque form input to output shaft in both directions of rotation, but restrains any feedback torque of the driven load from rotating the output shaft in either direction. This study was carried out to demonstrate through finite element methode and durability estimation for safety of the R-L clutches without sliding during the engagement process. As results, we organized about endurance test methode when applied rated torque.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.66-71
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• 2004

Estimation of the CANDU pressure tube deflection is important since the deflection may cause significant structural failure due to hydrogen diffusion and blister. However, there is no appropriate engineering model to estimate it exactly. The purpose of this paper is to propose a new analysis method and program to resolve this issue. For development of proper analysis method, a series of finite element analyses has been carried under elastic-creep condition. In addition, for effective estimation of the creep deflection, an analysis program named PC-DAS was developed based on the proposed method. Comparison of simple case study results with corresponding reference ones showed good agreement. Therefore, the proposed method and program can be utilized as one of valuable toolkit for integrity assessment of CANDU pressure tube.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.6 s.171
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• pp.47-54
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• 2005

A dangerous event occurred at the field industry and mechanical system. At developed by SUNGGOKNANOTECH corp. a R-L clutches of a small and high capacity serves safety device from a variety environment of mechanical system, it permits transmission of driving torque from input to output shaft in both directions of rotation, but restrains any feedback torque of the driven load from rotating the output shaft in either direction. This study was carried out to demonstrate through finite element method and durability estimation for safety of the R-L clutches without sliding during the engagement process. As results, we organized about endurance test method when applied rated torque.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.5
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• pp.850-858
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• 1997

A new a posteriori error estimator is introduced and applied to variational inequalities occurring in problems of flow through porous media. In order to construct element-wise a posteriori error estimates the global error is localized by a special mixed formulation in which continuity conditions at interfaces are treated as constraints. This approach leads to error indicators which provide rigorous upper bounds of the element errors. A discussion of a compatibility condition for the well-posedness of the local error analysis problem is given. Two numerical examples are solved to check the compatibility of the local problems and convergence of the effectivity index both in a local and a global sense with respect to local refinements.

• Journal of Mechanical Science and Technology
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• v.19 no.2
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• pp.625-633
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• 2005

A finite element vibration analysis of thin-walled cylindrical shells conveying fluid with uniform velocity is presented. The dynamic behavior of thin-walled shell is based on the Sanders' theory and the fluid in cylindrical shell is considered as inviscid and incompressible so that it satisfies the Laplace's equation. A beam-like shell element is used to reduce the number of degrees-of-freedom by restricting to the circumferential modes of cylindrical shell. An estimation of frequency response function of the pipe considering of the coupled effects of the internal fluid is presented. A dynamic coupling condition of the interface between the fluid and the structure is used. The effective thickness of fluid according to circumferential modes is also discussed. The influence of fluid velocity on the frequency response function is illustrated and discussed. The results by this method are compared with published results and those by commercial tools.

• Korean Journal of Construction Engineering and Management
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• v.24 no.1
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• pp.31-39
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• 2023

To reduce facility management costs and safety concerns due to aging of facilities, it is important to estimate the future facilities' condition based on facility management data and utilize predictive information for management decision making. To this end, this study proposed a methodology to estimate facility elements' condition using XGBoost. To validate the proposed methodology, this study constructed sample data for road bridges and developed a model to estimate condition grades of major elements expected in the next inspection. As a result, the developed model showed satisfactory performance in estimating the condition grades of deck, girder, and abutment/pier (average F1 score 0.869). In addition, a testbed was established that provides data management function and element condition estimation function to demonstrate the practical applicability of the proposed methodology. It was confirmed that the facility management data and predictive information in this study could help managers in making facility management decisions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.12 s.255
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• pp.1618-1625
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• 2006

During the last two decades, several guidelines have been developed and used for assessing the integrity of a defective steam generator (SG) tube that is generally caused by stress corrosion cracking or wall-thinning phenomenon. However, as some of SG tubes are also failed due to fretting and so on, alternative failure estimation schemes are required for relevant defects. In this paper, parametric three-dimensional finite element (FE) analyses are carried out under internal pressure condition to simulate the failure behavior of SG tubes with different defect configurations; elliptical wear, tapered and flat wear type defects. Maximum pressures based on material strengths are obtained from more than a hundred FE results to predict the failure of SG tube. After investigating the effect of key parameters such as defect depth, defect length and wrap angle, simplified failure estimation equations are proposed in relation to the equivalent stress at the deepest point in wear region. Comparison of failure pressures predicted by the proposed estimation scheme with corresponding burst test data showed a good agreement.

• Journal of the Society of Naval Architects of Korea
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• v.56 no.3
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• pp.217-230
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• 2019

In this study, a fatigue damage estimation for an ice-going vessel navigating through broken ice fields was carried out. A numerical model to simulate the interaction between ice and structure developed using the finite element method was introduced. Time series of stresses calculated by the proposed model and the corresponding fatigue analysis results are presented. The numerical model enables the long time analysis through an efficient interaction model, the application of the periodic media analysis and the convolution integral, and it allows the stress time history to be extracted directly using the finite element method. To describe the probability distribution of stress amplitudes, the 2-parameter Weibull model was applied to the calculated stress time history, and the fatigue damage was calculated using the Palmgren-Miner rule. Finally, the fatigue damage considering the ice conditions of the Baltic Sea was calculated using the proposed method and LR method, and the results were compared to each other.