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[차량운동성능부문] 자유도 축소 변형모드를 이용한 유연 다물체 동역학 새헉
김효식(H.S.Kim),김창부(C.B.Kim) 한국자동차공학회 2001 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2001 No.11_2
This paper presents an efficient method for dynamic analysis of flexible multibody system. The proposed method is flexible multibody dynamic analysis using deformation modes with reduced degrees of freedom. The deformation modes of a flexible body arc obtained efficiently through finite clement analysis using reduction method of nodal degrees of freedom. The effectiveness of the proposed method IS verified In numerical examples of the high-speed rotating beam and a bump-passing mini-bus
[구조강도부문] 차체구조의 내구 설계 및 평가를 위한 전산 통합 해법
김효식(H.S.Kim),김창부(C.B.Kim),임흥재(H.J.Yim) 한국자동차공학회 2001 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2001 No.11_2
This paper presents a computer-integrated method for durability design and estimation in order to confirm durability of the body structure in the city bus. The proposed method gains the optimal design of the body structure through iterative cycles of two phases. The first phase is for durability estimation cycle. which is carried out by use of a computational durability analysis. The other one is for durability design cycle. which is executed by use of optimal design method. The final optimal design is resulted from several iterations of estimation and design cycle. The durability confirmation under a real service environment in Seoul city is followed by the final design.
김효식(H.S.Kim),여은구(Y.E.Ku) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Wear is a complex and difficult phenomenon to treat analytically. However, in automotive industry, it is necessary to design brake system by use of cost effective analytical methods to improve quality of<br/> frictional materials. The problem of abnormal wear of frictional materials in automotive brake system is typically caused by quality defects in manufacturing. This quality problem, however, can't be controlled deterministically and requires analyses and designs considering uncertainties. This paper presents a method for dynamic analysis of the abnormal wear of frictional materials considering uncertainties. Firstly, quality defects, which come from the uncertainties, arc determined by examination of sensitivities of the brake quality factors. Effective quality defects arc selected by both investigation of process capability and comparison of sensitivity of each quality defects. Noise levels of the effective quality defects arc determined. Secondly, f1exible multibody dynamic analysis and finite element analysis arc carried out to predict wear pattern considering the quality defects in the proposed method. Finally, the analysis results are compared with the test results using a brake dynamo test system.<br/>
김효식(H.S. Kim),황용서(Y.S. Hwang),윤호상(H.S. Yoon),김창부(C.B. Kim),임홍재(H.J. Yim) 한국자동차공학회 2000 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Durability estimation of a prototype vehicle has traditionally relied heavily on accelerated durability tests using predefined proving grounds. By use of those accelerated tests, it is very difficult to predict durability failures in an actual service environment. This motivated the development of an integrated CAE(Computer Aided Engineering) methodology for the durability estimation of a prototype vehicle in actual service environments. Since expensive computational costs such as computation time and hardware resources are required for a full vehicle simulation in those environments with a very long span of event time, the conventional CAE methodologies have little feasibility. An efficient computational durability estimation method is presented with theoretical and technique developments.
차체의 피로 수명 예측을 위한 변형 모드 선택에 관한 연구
김효식(H.S.Kim),황용서(Y.S.Hwang) 한국자동차공학회 1998 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1998 No.5_2
This paper considers the method of computational simulation to predict durability of a vehicle body at an early stage in design steps. There are three fundamental steps in this simulation approach. The first step is to measure the acceleration history. which will be used for road excitation at the next step, of axle spindles on the Belgian block. The second step is to define the dynamic environment of a global vehicle. The final step is to establish the load-stress relationship of the local area and to determine the life prediction. The spatial DADs code are used to calculate the dynamic load history of a vehicle on Belgian road with 25KPH. We Present the results and effect of deformation mode selection with vibration modes and static modes on accuracy and computational cost of dynamic analysis.
Computational Durability Estimation of a Prototype Vehicle
H. S. Kim(김효식),C. B. Kim(김창부),H. J. Yim(임홍재) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.3
Durability estimation of a prototype vehicle has traditionally relied heavily on accelerated durability tests using predefined proving grounds. By use of those accelerated tests, however, it is very difficult to predict durability failures in an actual service environment. This motivated the development of an integrated CAE(Computer Aided Engineering) methodology for the durability estimation of a prototype vehicle in actual service environments. Since very expensive computational costs such as computation time and hardware resources are required for a full vehicle simulation in those environments, the conventional CAE methodologies have little feasibility. An efficient computational methodology for durability estimations is presented with theoretical and technique developments.
용접부 내구모델을 이용한 신개념 버스 차체구조의 피로수명 예측
김효식(H.S Kim),김태진(T.J Kim),김창부(C. B Kim) 한국자동차공학회 2002 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2002 No.5_2
차체구조를 구성하는 여러 부재를 연결하는 주요한 방법으로서 용접, 리벳 밋볼팅둥의 방법들이 사용되고 있다. 주지하다시피 내구문제의 90%이상이 이러한 연결부에서 또는 연결부로 인해서 발생하고 있다. 따라서 차체구조의 내구력을 예측하기 위해서는 연결부들의 내구해석에 대한 기술이 확보되어야 한다. CNG 연료를 사용하는 도시형버스의 개발에 있어서, 승객의 편의성을 확보차기 위해서 기존에 Frame에 장착된 CNG 연료탱크를 차체의 지붕에 장착하는 설계 레이아웃이 필요하게 된다. 이러한 설계 레이아웃은 차체구조의 하중배분을 변경시키고 차량의 무게중심을 상승시켜서 차량의 핸들링성능 및 저주파수 진동성능 등을 포함하여 차체구조의 내구력에 큰 영향을 미치게 된다. 따라서 설계 초기단계에서 차체구조의 내구력을 고려만 구조 강성설계가 수행되어야 하며 차체구조의 내구력을 예측하기 위해서는 차체구조내 연결부 특히 Spot, Plug및 Seam 용접부등과 볼트 및 리벳 체결부 둥의 내구력 예측에 관한 연구가 필요하다. 본 연구에서는 용접부 및 체결부등에 데한 내구 모델을 제안하고 Roof on CNG 버스 차제구조의 내구해석용 유한요소모델에 적용한 후, 실차내구시험조건인 벨지안모드하에서 계산된 동하중 시간미력들을 이용하여 다축하중을 고려한 자체구조의 내구력을 예측하고자 한다. 여기서 용접부의 유한요소 모델 및 피로물성 데이타는 해석 및 시험으로부터 구해진 결과들을 이용해서 제작되었으며 피로수명평가용 전용프로그램인 FEMFAT를 이용해서 고려하였다. <br/>