저자명 김현섭 
년도 2000 
Thin-walled structures are widely used as structural members for the purpose of energy absorption. The most important aspects in the plastic design of these structural members for safety and reliability are their load-carrying capacity under various types of loading and corresponding collapse modes and energy absorption rate. The plastic design method of thin-walled structures can be divided into analytical method and numerical method. The analytical method assumes concentrated deformation at the plastic hinge and obtains collapse mechanism and semi-empirical equation for calculating the collapse load. Although the determination of location and configuration of the plastic hinge becomes very important, it is very difficult to presume the location and configuration of the plastic hinge in complicated structures. As an alternative, numerical method is necessary for collapse analysis of thin-walled structures under various conditions.
  The numerical method consists of the incremental elasto-plastic finite element analysis, the incremental rigid-plastic finite element analysis and the finite element limit analysis. Although the elasto-plastic analysis can provide relatively detailed information, the analysis requires large amount of memory for the storage of stress state and much time to check whether yielding occurs. Step increments for the analysis should be small enough to ensure stable convergence and reliable solutions. On the other hand, finite element limit analysis has capability to calculate the collapse load and the collapse mode of complicated structures without any prior conjectures under the assumption that elastic deformation is small enough to be negligible. The analysis with a simple formulation has the advantage of stable convergence, computational efficiency and easy access to work-hardening materials compared to an elasto-plastic analysis. The solution procedure of finite element limit analysis obtains the proportional loading factor by minimizing the dual functional that can also be regarded as the plastic dissipation energy. Since the analysis is waived from tracking the stress-strain curve and obtaining the tangent modulus, it allows relatively large step size without losing the solution reliability. Finite element limit analysis can be efficiently used to predict plastic collapse loads and collapse modes of thin-walled structures with strain-hardening materials.
  In this paper, the finite element limit analysis with the degenerated four-node shell element is formulated based on the duality theorem in plasticity. For computational efficiency, the reduced integration technique is employed with the physical stabilization scheme that does not need any user-defined parameter for hourglass control. The analysis considers sequential deformation of structures with strain-hardening. To verify the efficiency of the present analysis method, the collapse analysis of square tube and S-rail was simulated using the finite element limit analysis code.
  The axial crushing tests of square tubes were conducted with specified cross-section and various width/height ratios. The cross-section of the test specimens is assigned to correspond to the inextensional and compact mode that shows good energy absorption efficiency. To achieve the quasi-static loading condition, the tests were performed at cross-head speeds of 1mm/min. Finite element limit analysis results are compared with experimental results in order to determine the accuracy in prediction of load-carrying capacity and deformation modes. The comparison demonstrated that finite element limit analysis results are reliable even with relatively large step increments. The large step increment well described continuous folding of square tubes with the appropriate contact treatment.
The collapse analysis of an S-rail was performed using the finite element limit analysis code and its results were compared with elasto-plastic analysis results using the explicit dynamic code PAMCRASH. In view of computational efficiency, the finite element limit analysis was very effective for the structural collapse analysis in comparison of computation time and solution quality with those obtained from an elasto-plastic analysis. The collapse analysis of an S-rail was conducted with variation of the thickness under the specified geometry to estimate the energy absorption capacity with respect to the sheet thickness as a design parameter. The energy absorption ratio with respect to the thickness ratio was found to be well approximated with a quadratic equation. This formula can be used effectively to aid design improvement at the initial stage of the structural design. The collapse analysis result showed that the energy absorption efficiency of the structure was remarkably increased with the stiffened S-rail and effective design improvement could be achieved through adequate stiffening of structures.

번호 제목 저자명 날짜 조회 수
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» Shell Element Formulation for Limit Analysis of Thin-Walled Structures ( 박판부재의 붕괴거동해석을 위한 극한해석의 쉘요소 수식화 ) 김현섭  2005.11.29 16260
23 Finite Element Simulation of 3-dimensional Superplastic blow forming with diffusion bonding (유한요소법을 이용한 초소성 재료의 삼차원 확산 접합 및 압력 성형 해석) 이기석  2005.11.29 18463
22 Crash Analysis of Auto-body Structures with an Explicit Finite Element Method ( 외연적 유한요소법을 이용한 차체 구조물의 충돌해석 ) 강우종  2005.11.29 18137
21 Optimum Process Design in Sheet Metal Forming Processes using Finite Element Sensitivity Analysis (유한요소 민감도해석을 이용한 박판금속성형에서의 공정변수 최적설계) [1] 김세호  2005.11.29 20324
20 Development of a Nonlinear Degenerated Shell Element with the Drilling Degree of Freedom by the Cubic Polynomial Interpolation and the Assumed Strain Method (드릴링 자유도의 삼차 근사법과 대체변형률법을 이용한 비선형 감절점 쉘 요소의 개발) 이형욱  2005.11.29 19216
19 Finite Element Inverse Approach and Initial Guess Generation for Sheet Metal Forming Analysis of Complicated Auto-body Members (복잡한 차체부재의 박판성형공정을 위한 유한요소 역해석 및 초기추측치 계산) 김승호  2005.11.29 20636
18 Dynamic Formulation of Finite Element Limit Analysis for Impact Simulation of Structural Members (구조부재의 충돌해석을 위한 유한요소 극한해석의 동적 수식화) 김기풍  2005.11.29 19191
17 Study on Dynamic Tensile Tests of Auto-body Steel Sheet at the Intermediate Strain Rate for Material Constitutive Equations (차체강판의 중변형률 속도에서의 동적 인장시험 및 물성 구성방정식에 관한 연구) 임지호  2005.11.29 27388
16 A Study on the Dynamic Failure Model of a Spot Weld under Combined Loading Conditions for Auto-body Crash Analyses (차체용 부재의 충돌해석을 위한 복합하중조건에서 점용접부의 동적 파단모델 연구) [1] 송정한  2008.07.24 20490
15 Analysis of Elasto-Plastic Stress Waves by a Time Discontinuous Variational Integrator of Hamiltonian with a Second-Order Integration Scheme of the Constitutive Model (해밀토니안의 시간 불연속 변분적분기와 구성방정식의 2차 정확도 적분법을 이용한 탄소 조상순  2008.12.15 23150
14 Microscopic investigation of the strain rate hardening for auto-body steel sheet(차체강판 변형률속도 경화의 미시적 관찰) 윤종헌  2010.07.13 18601
13 A Study on Material Properties of OFHC Copper Film at High Strain Rates using High-Speed Micro Material Testing Machine (고속마이크로재료시험기를 이용한 무산소동 박판의 고변형률속도 재료물성치 연구) 김진성  2010.07.13 21965
12 Evaluation of a cast-joining process of dual metal crankshafts for heavy-duty engines with ductile cast iron and high strength forged steel(구상흑연주철과 고강도 단조강의 주조접합 이종금속을 이용한 중대형 엔진 크랭크샤프트의 평가) 한 신  2010.07.13 19388
11 Forming Limit Diagram of Auto-body Steel Sheets at High Strain Rates for Sheet Metal Forming and Crashworthiness (박판성형 및 충돌성능 향상을 위한 고변형률속도에서의 차체강판 성형한계도) 김석봉  2010.07.13 23184
10 A Study on the Tension/Compression Hardening Behavior of Auto-body Steel Sheets Considering the Pre-strain and the Strain Rate (초기 변형률 및 변형률 속도를 고려한 차체 강판의 인장/압축 경화 거동에 관한 연구) [1] 배기현  2011.01.11 22497
9 A Study on a Continuum Damage Yield Function to Predict Ductile Fracture of Materials (재료의 연성파단을 예측하기 위한 연속체 손상 항복 함수에 관한 연구) 고윤기  2012.12.10 16152
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