선용접방법으로 제작된 16×16 최적화 H형 스프링 지지격자에 대한 진자식충격시험

김재용(J-Y Kim),윤경호(K-H Yoon),송기남(K-N Song) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5

The General roles of a spacer grid(SG) are providing a lateral and vertical support for fuel rods, promoting a mixing of coolant and keeping guide tubes straight so as not to impede a control rod insertion under any normal or accidental conditions. To evaluate the impact characteristics of a SG such as impact velocity, critical buckling strength and duration time, a few types of impact tests for SGs have been conducted. In a previous study, a new welding method, a through-welding method, was proposed to increase critical buckling strength of a SG without any design change or material change and was verified by impact tests with 1×7 partial SG specimens. In this paper, the effect of through-welding method in case of a 16×16 full-size SG is investigated by pendulum impact tests with 16×16 SG specimens. And the increase of critical buckling strength for full-size SGs is measured by comparison with impact results of spot-welded and through-welded SGs.

자유낙하에 의한 경수로용 핵연료집합체의 동적 거동 해석

윤경호(K-H Yoon),김형규(H-K Kim),전태현(T-H Chun),안창기(C-K Ahn) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11

The objective of this research is to propose the methodology that could predict the dynamic failure behavior on the pressurized water reactor (PWR) fuel assembly structure for the reactor coolant pump (RCP) over-speed transient event. To perform this objective, the finite element analysis method for predicting the axial impact behavior on the fuel structure is established by a commercial finite element codes ANSYS and DYNA-3D. In this FE analysis method, appropriate boundary conditions and impact loading conditions are applied to simulate the actual core conditions. The drop impact analysis of a fuel assembly for PWR power plant is executed by the finite element analysis method. The analysis results are compared with the previous experimental results. The impact force results differed from the analysis condition depending on how many fuel rods slipped down to the bottom nozzle. And the joint and connection parts between components of a fuel assembly are very important for determining the stiffness of it. In the analysis, the fuel assembly experienced an impact force of approximately 111.53 kN when dropped from a height 25 mm with the fuel rods on the bottom nozzle. The secondary peak value is about 57.55 kN and the duration is about 6 milliseconds. After comparing with the previous test results, the developed finite element model and analysis procedure will be useful tool for evaluating the dynamic stiffness and strength of a fuel assembly. It is found that the joint and connection characteristics among parts are dominant factor which determine the non-linear behavior of a fuel during free fall event.

유한요소법에 의한 경수로용 핵연료집합체의 낙하충격 해석

윤경호(K-H Yoon),안창기(C-K An),이강희(K-H Lee),송기남(K-N Song) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11

The drop impact analysis of a fuel assembly for pressurized water reactor (PWR) power plant is executed by finite element analysis method. The used commercial FE codes are the ANSYS and LS-DYNA3D. The analysis results are compared with the previous experimental results. The impact force results differed from the analysis condition depending on how many fuel rods slipped down to the bottom nozzle. And the joint and connection parts between components of a fuel assembly are very important for determining the stiffness of it. The fuel assembly experienced an impact force of approximately 95.65kN when dropped from a height 25 ㎜ with the fuel rods off the bottom nozzle. The developed finite element model and analysis procedure will be useful tool for evaluating the stiffness and strength of a fuel assembly.

익형 동체의 하강기류(Down-wash)가 공기역학적 특성에 미치는 영향에 관한 수치해석연구

윤경호(K.H. Yoon),김철호(C.H. Kim) 한국전산유체공학회 2013 한국전산유체공학회지 Vol.18 No.3

Drag reduction of a running vehicle is very important issue for the energy savings and emission reduction of its power train. Especially for a solar powered electric vehicle, the drag reduction and weight lightening are two serious problems to be solved to extend its driving distance under the given energy condition. In this study, the ground effect of an airfoil shaped road vehicle was studied for an optimum body design of an ultra-light solar powered electric vehicle. Clark-Y airfoil type was adopted to the body shape of the model vehicle to reduce aerodynamic drag. From the study, it was found that the drag of the model vehicle was reduced as the height(h) between ground and the lower surface of the model vehicle was decreased. It is due to the reduction of the down-wash decreasing the induced drag of the vehicle. The lift was also decreased as the height decreased. It is due to the turbulent boundary layer developed beneath the vehicle body. The drag is classified into two types; the form and friction drag. The fraction of form drag to friction one is 76 to 24 on the model vehicle. As the height(h) of the model vehicle from the ground surface increases the form drag also increases but the friction drag is in reverse.

다중 구속조건을 고려한 격자체 구조물의 충격해석 모델개선

윤경호(K-H Yoon),강흥석(H-S Kang),김형규(H-K Kim),송기남(K-N Song) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5

The dynamic impact analysis is performed for predicting the buckling behavior of a grid structure under the lateral<br/> impact load by finite element method. The grid structure is composed of several thin plates which were inserted each<br/> other and then each contact places were welded by laser welding. The finite element model is produced using preprocessor<br/> I-DEAS, and solved using nonlinear commercial solver ABAQUS/explicit. In this work, two models are<br/> proposed for FE analysis. One is the simplified model and the other is multi constrained one. Applied boundary<br/> conditions for dynamic impact analysis were nearly the same with actual boundary conditions for impact test. The<br/> dynamic impact parameters of a grid structure such as critical impact acceleration, impact force and buckling mode and<br/> so on, are over-estimated with test results. Based on these results, the FE analysis model of the grid structure is need to<br/> modify the stiffness of a grid cell structure. According to these results, the FE model is modified for estimating the<br/> buckling behavior of grid structure. This modified FE model will be compared with test and analysis results using the<br/> simplified model.

측면충격하중 상태에서 격자구조물의 좌굴거동 해석모델 개선

윤경호(K-H Yoon),허성필(S-P Heo),강흥석(H-S Kang),김형규(H-K Kim),송기남(K-N Song) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.8

The drop type impact test and finite element analysis are established for examining the buckling behavior of a grid structure under the lateral impact load. This grid structure is composed several thin plates by laser welding. The finite element model is produced using preprocessor I-DEAS, and solved using nonlinear solver ABAQUS/explicit. Applied boundary conditions for dynamic impact analysis were nearly the same with actual boundary conditions for impact test. However, the dynamic impact parameters of a grid structure are good agreement with test results. Based on these results, the analysis model of the grid structure for FE analysis is adaptable for evaluating the dynamic buckling behavior of a grid structure. These test and analysis results will be adaptable for predicting the dynamic structural integrity of a grid structure not only the axial impact event but also the lateral impact event.

측면충격하중 하에서 격자체 구조물의 좌굴거동 해석모델

윤경호(K-H Yoon),강흥석(H-S Kang),김형규(H-K Kim),송기남(K-N Song),김우곤(W-G Kim) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.3

The drop type impact test and finite element analysis are established for examining the buckling behavior of a grid structure under the lateral impact load. This grid structure is composed several thin plates by laser welding. The finite element model is produced using preprocessor I-DEAS, and solved using nonlinear solver ABAQUS/explicit. Applied boundary conditions for dynamic impact analysis were nearly the same with actual boundary conditions for impact test. However, the dynamic impact parameters of a grid structure are good agreement with test results. Based on these results, the analysis model of the grid structure for FE analysis is adaptable for evaluating the dynamic buckling behavior of a grid structure. These test and analysis results will be adaptable for predicting the dynamic structural integrity of a grid structure not only the axial impact event but also the lateral impact event.

전산유체역학을 이용한 고속로용 제어봉집합체의 설계 최적화

윤경호(K.H. Yoon),김재용(J.Y. Kim),오세홍(S.H. Oh),최청열(C.R. Choi) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11

CFD analysis of the control rod assembly for sodium-cooled fast reactor is introduced. The experimental method of the mock-up CRA was established under submerged water condition to validate the analysis model and method. The design optimization of the CRA was carried out using validated analysis model and method. The optimization variables are drop time and damping performance of a damper. The revised design was satisfied with these design variables.

측면 충격하중 하에서 격자체 형태에 따른 좌굴거동

윤경호(K-H Yoon),이강희(K-H Lee),송기남(K-N Song) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.3

The pendulum type impact test is established for evaluating the buckling behavior of a grid structure under the lateral impact load. This grid structure is composed several thin plates by laser welding. The test data acquired as initial impact angular, which were impact acceleration, force and duration time. These critical buckling strength are affected the configuration of grid structure. The cylindrical tube insertion case with fuel rod cell showed higher strength than that of the empty grid structure. And the thicker cylindrical tube insertion case with guide tube cell also represented a little higher value than that of the only fuel rod tube configuration case. Even though, the support condition of the grid structure was non-linear characteristic behavior due to friction force between two parts, these cylindrical tube cases expressed much higher than that of the only shell structure case. When the design criteria for the seismic and accident event will be raise in next generation fuel, it needs more robust design grid structure by shape optimization of the strap and joint connection method re-design.

경수로용 고유 지지격자 스프링의 탄소성 특성해석 및 시험

송기남(K-N Song),허성필(S-P Heo),윤경호(K-H Yoon),강홍석(H-S Kang),정연호(Y-H Jung) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.8

The elastic-plastic characteristic of the spacer grid spring in a nuclear fuel assembly is important to evaluate the supporting capability of a fuel rod. However, the characteristic for the fuel assembly design is usually obtained from the test. In this paper, the finite element analyses on the KAERI designed spacer grid springs are performed in order to get their characteristic curves. The appropriate boundary condition in the characteristic analysis of a spacer grid spring is proposed by comparisons with test results.