[論文] 벨로우즈 문제 해석을 위한 수정 에너지 이론

이완익(Wan Ik Lee),김태완(Tae Wan Kim) 한국자동차공학회 1989 오토저널 Vol.11 No.2

In this paper, the bellows problem under axial load were investigated. A modified energy theory, which has the improved strain energy and stress description taken from governing equation of general shells of revolution, were proposed.From the analysis, the results obtained from the modified theory were more accurate and in stable state with varing geometric parameter of bellows than those of other theory.

[論文] 유한 요소법을 이용한 Bellows Joint의 응력해석

이완익(Lee Wan-ik),김태완(Kim Tae-wan) 한국자동차공학회 1987 오토저널 Vol.9 No.4

The Bellows Joint which was used as a absorber or safety equipment to prevent the de­formation or fracture of a structure, have been analyzed by the F.E.M using axi-symmetric conical frustum element. Using the F.E.M the general behavior of Bellows Joint corrugation can be investigated easily, and the stability of the analysis be guaranteed. In annular type corrugation, the F.E.M results were agreed with those of other theoretical analyses, but in the U type corrugation, the F.E,M results were more acceptable than those of others.

자동차 배기계 설계를 위한 엔진운동변위 산출에 관한 연구

이완익(W. I. Lee),박경진(K. J. Park),이권희(K. H. Lee) 한국자동차공학회 1993 한국 자동차공학회논문집 Vol.1 No.1

가변 샌드위치 구조물의 형상최적설계

박철민,박경진,이완익 대한기계학회 1993 대한기계학회논문집 Vol.17 No.9

Geneal Structure optimization is utilized to minimize the weight of structures while satisfying constraints imposed on stress, displacements and natural frequencies, etc. Sandwich structures consist of inside core and outside face sheets. The selected sandwich structures are isotropic sandwich beams and isotropic sandwich plate. The face sheets are treated as membrane and assumed to carry only tensions, while the core is assumed to carry only transverse shear. The characteristic of the varying area are considered by adding the projected component of the tension to the transverse shear. The bending theory and energy method are adopted for analyzing sandwich beams and plates, respectively. In the optimization process, the cost function is the weight of a structure, and a deflection and stress constraints are considered. Design variable are thickness and tapering coefficients which determine the shape of a structure. An existing optimization code is used for solving the formulated problems.

벨로우즈 해석을 위한 유한요소의 개발에 관한 연구

고병갑,박경진,이완익 한양대학교 공학기술연구소 1995 공학기술논문집 Vol.4 No.1

Bellows is a familiar component in piping systems as it provides a relatively simple means of absorbing thermal expansion and providing system flexibility. In routine piping flexibility analysis by finite element methods, bellows is usually considered to be straight pipe runs modified by an appropriate flexibility factor; maximum stresses are evaluated using a corresponding stress concentration factor. The aim of this study is to develop a bellows finite element, which similarly includes more complex shell type deformation patterns. This element also does not require flexibility or stress factors, but evaluates more detailed deformation and stress patterns. The proposed bellows element is a 3-D, 2-noded line element, with three degrees of freedom per node and no bending. It is formulated by including additional 'internal' degrees of freedom to account for the deformation of the bellows corrugation; specifically a quarter toroidal section of the bellows, loaded by axial force, is considered and the shell type deformation of this is include by way of an approximating trigometric series. The stiffness of each half bellows section may be found by minimising the potential energy of the section for a chosen deformation shape function. An experiment on the flexibility is performed to verify the reliability for bellows finite element.

벨로우즈 형상의 최적설계에 관한 연구 -원형벨로우즈를 중심으로-

고병갑,박경진,이완익 한국자동차공학회 1991 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

원자력발전소, 중화학 플랜트등의 배관계통이나, 항공기및 자동차의 배기계농에서는 축방향 하중과 고온 고압의 유체로 인한 변형이나 파손이 자주 발생한다. 이러한 배기 배관계통의 변형이나 파손을 방지하기 위하여 신축이음의 일종인 벨로우즈가 널리 사용되고 있다. 본 연구에서는 이러한 축방향 하중을 받는 원형벨로우즈의 형상을 최적화하였다. 벨로우즈의 이론적 구조해석으로는 토로이달쉘부분에 에너지법을 사용한 Laupa의 해석이론을 기초로 하였고, 최적설계로는 벨로우즈 반지름과 파형 반지름과의 비 λ와 두께를 최적설계변수로 채택하였다. 또한 축방향변위를 목적함수로 선정하여 이를 최대화하였으며, 제한함수로는 세가지를 고려하였다. 첫째는, 전단변형에너지설을 이용하여 구한 응력에 대한 제한함수이고 둘째는, 압축하중을 받는 경우 파형의 겹침을 방지하기 위하여 제한함수를 고려하였고 세째로는, 토로이달쉘요소의 좌굴을 방지하기 위하여 Hutchinson의 좌굴식을 제한함수로 고려하였다. 이와 같은 이론적 구조해석과 형상의 최적화를 통하여 현재 산업현장에서 사용되고 있는 원형 벨로우즈의 설계값과 본 논문에서 고찰한 최적화된 설계값을 비교 검토함으로써 사용 용도 및 조건에 맞는 적정형상과 이에 따르는 안전성 및 경제성을 도출하고 원형벨로우즈 선택의 기본자료를 제시하였다. Bellows which is utilized for a expansion Joint is being widely used in piping system of the nuclear reactor plants and exhaust system of the vehicle. This paper attempts to optimize shape of annular type bel lows under axial load and the results are compared with the existing shape. A theoretical structural analysis employs Laupa' s theory using energy method for the toroidal section. A procedure for shape optimization adopts λ, the ratio of bellows radius to corrugation radius, and a thickness as optimal design variables. The axial displacement is chosen for the objective function and is maximized. The constraints are imposed on the stress of the structure using maximum distortion energy method. The displacement and buckling constraint are also considered to prevent overlap of corrugation and the buckling of the toroidal section. The characteristics of the bellows structure is investigated through the optimal design process.

배관시스템 해석을 위한 벨로우즈 유한요소의 개발

고병갑,박경진,이완익 대한기계학회 1995 대한기계학회논문집 Vol.19 No.6

Bellows is a familiar component in piping systems as it provides a relatively simple means of absorbing thermal expansion and providing system flexibility. In routine piping flexibility analysis by finite element methods, bellows is usually considered to be straight pipe runs modified by an appropriate flexibility factor; maximum stresses are evaluated using a corresponding stress concentration factor. The aim of this study is to develop a bellows finite element, which similarly includes more complex shell type deformation patterns. This element also does not require flexibility or stress factors, but evaluates more detailed deformation and stress patterns. The proposed bellows element is a 3-D, 2-noded line element, with three degrees of freedom per node and no bending. It is formulated by including additional 'internal' degrees of freedom to account for the deformation of the bellows corrugation; specifically a quarter toroidal section of the bellows, loaded by axial force, is considered and the shell type deformation of this is include by way of an approximating trigonometric series. The stiffness of each half bellows section may be found by minimising the potential energy of the section for a chosen deformation shape function. An experiment on the flexibility is performed to verify the reliability for bellows finite element.

샌드위치 구조물의 형상최적설계

박철민,박경진,이완익 한양대학교 공학기술연구소 1992 공학기술논문집 Vol.1 No.1

General structural optimization is utilized to minimize the weight of structures while satisfying constraints imposed on stress, displacements and natural frequencies, etc.. Sandwich structures consist of inside core and outside face sheets. The selected sandwich structures are isotropic sandwich beams and isotropic sandwich plate. The face sheets are treated as membrane and assumed to carry only tensions, and the core is assumed to carry only the transverse shear. The characteristics of the varying area are considered by adding the projected component of the tension to the transverse shear. The bending theory and energy method are adopted for analyzing sandwich beams and plates, respectively. In the optimization process, the cost function is the weight of a structure, and a deflection and stress constraints are considered. Design variables are thickness and tapering coefficients which determine the shape of a structure. An existing optimization code is used for solving the formulated problems.

J적분을 이용한 복합조직강의 파괴인성 평가

김정규,오재민,이완익 대한기계학회 1984 대한기계학회 춘추학술대회 Vol.- No.-

J積分法 을 이용한 複合組織鋼 의 破壞靭性評價

김정규,오재민,이완익 대한기계학회 1984 대한기계학회논문집 Vol.8 No.5

본 연구에서는 구조물 경량화재료로서 변형거동이 현저히 다른 마르텐사이트 와 페라이트로 이루어진 복합조직강의 파괴인성에 관한 기본적 자료를 얻기 위하여 이 강을 모델재로서 준비하고 균열선단에서의 미시파괴기구 및 JSME Sool의 평가법을 이 용한 파괴인성에 대하여 검토하였다. In dual phase steel composed of martensite and ferrite which are different in deformation behavior, the quantitative estimation of fracture toughness is investigated by the R-curve method and the stretched zone method of JSME Sool. In the homogeneous material J$_{IC}$ value measured by the R-curve method and the stretched zone method are almost equivalent each other, but in the inhomogeneous material J$_{IC}$ value by the stretched zone method is overestimated than that by the R-curve method. Such a overestimation for the J$_{IC}$ is due to the continuous plastic blunting of ferrite after the stretched zone width in martensite reached critical value which overmeasures the critical stretched zone width.width.