저자명 김기풍 
년도 2003 
Structural members of a vehicle are designed to increase the energy absorption efficiency and thus to enhance the safety and reliability of a vehicle. The crashworthiness of each member needs to be evaluated at the initial stage of vehicle design for good performance of an assembled vehicle. As the dynamic behavior of structural members is different from the static one, the crashworthiness of vehicle structures has to be assessed by numerical impact analysis considering the dynamic response related to the inertia and strain-rate hardening effect. Impact simulation is usually carried out with the elastic-plastic finite element analysis code such as PAMCRASH or LS-DYNA3D. It inevitably requires tremendous time and efforts to estimate the crashworthiness of structural members even with the explicit methods. An efficient, alternative analysis tool could be an extended limit method for fast evaluation of the crashworthiness of structural members.
  Limit analysis has become a useful and efficient numerical tool in the collapse behavior assessment for structural members since the method can easily calculate the plastic collapse load, energy absorption and deformation mode. The conventional limit analysis method seems seldom applied to real complicated structural problems probably because of the limitation of the method. However, a burst of development in limit theories and computer technologies enable limit analysis applied to complicated structural problems. Especially, the limit analysis concept has extended to a class of work-hardening materials from its long conjecture of perfectly plastic materials. Although the algorithm with a simple formulation has the advantage of stable convergence, computational efficiency and easy access to work-hardening materials, the method has been developed only for static collapse behavior of structures. Development of dynamic limit analysis could make it possible to evaluate the crashworthiness of structural members efficiently, accurately and systematically.
  In this paper, the limit analysis concept is extended to incorporate with the dynamic equilibrium condition considering the inertia and strain-rate effects instead of the static equilibrium. A dynamic formulation of limit analysis has been derived for sequential incremental analysis dealing with time integration, strain and stress evaluation, strain hardening, strain-rate hardening and thermal softening. The time dependent term in the governing equation is integrated with the WBZ-α method proposed by Wood, Bossak and Zienkiewicz. The dynamic material behavior is described by the Johnson-Cook model in order to consider strain-rate hardening and thermal softening as well as strain hardening. The contact condition is added in order to check the penetration in the complicated structures.
  The analysis method developed has been applied to a class of impact analysis of structural members. The high velocity deformation analysis of the plate with a hole has been carried out in order to verify the accuracy and validity of the dynamic limit analysis and WBZ-α method. The impact analysis of a Taylor bar has been performed in order to comparing the rate-dependent constitutive model with the quasi-static constitutive relation. Impact analysis of an S-rail has been performed with the dynamic limit analysis code and the numerical results have been compared with elasto-plastic explicit analysis results by LS-DYNA3D for collapse loads and its deformed shapes as well as the strain distribution. Comparison demonstrates that the dynamic finite element limit analysis can predict the crashworthiness of structural members effectively with less effort and computing time than the commercial codes compared. The impact analysis of S-rails has been conducted with the variation of design parameters such as the thickness and the aspect ratio of cross-section in order to estimate the energy absorption ratio with respect to the design parameters.
  Numerical simulations have been carried out with a finite element limit analysis in order to identify forming effects on crash behavior of an S-rail. The formed S-rail contains fabrication histories such as residual stress, work hardening, non-uniform thickness distribution and geometric changes resulted from the forming process. Crashworthiness such as the collapse load, the deformed mode and the energy absorption has been investigated in order to identify forming effects. It is fully demonstrated that the design of auto-body structures needs to consider the forming effects for proper assessment of load-carrying capacity and deformation of the formed structures.
  The analysis results demonstrate that the dynamic limit analysis method is an effective and useful tool in the dynamic analysis and prediction of the crashworthiness of structural members.

번호 제목 저자명 날짜 조회 수
27 Sheet metal forming analysis with a modified membrane finite element formulation considering bending effect (굽힘 효과를 고려한 박막 요소 수식화에 의한 박판 성형 가공 해석) 한수식  2005.11.29 7583
26 Process parameter estimation in sheet metal forming using a finite element inverse method (유한요소 역 해석을 이용한 박판금속 성형의 공정변수 예측) 이충호  2005.11.29 7450
25 A Rigid-plastic Finite Element Analysis of Sheet Metal Forming with Planar Anisotropic Materials using a Modified Membrane Element considering Bending Effect (굽힘이 고려된 개량박막요소를 이용한 평면이방 박판금속 성형의 강소성 유한요소 해석) 최태훈  2005.11.29 8693
24 Shell Element Formulation for Limit Analysis of Thin-Walled Structures ( 박판부재의 붕괴거동해석을 위한 극한해석의 쉘요소 수식화 ) 김현섭  2005.11.29 14694
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 16942
22 Crash Analysis of Auto-body Structures with an Explicit Finite Element Method ( 외연적 유한요소법을 이용한 차체 구조물의 충돌해석 ) 강우종  2005.11.29 16677
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 18449
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 17670
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 19058
» Dynamic Formulation of Finite Element Limit Analysis for Impact Simulation of Structural Members (구조부재의 충돌해석을 위한 유한요소 극한해석의 동적 수식화) 김기풍  2005.11.29 17733
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 25435
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 18512
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 21652
14 Microscopic investigation of the strain rate hardening for auto-body steel sheet(차체강판 변형률속도 경화의 미시적 관찰) 윤종헌  2010.07.13 16893
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 20167
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 17832
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 21592
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 20281
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 14571
8 Measurement Uncertainty Evaluation for High Strain Rate Tensile Properties of Auto-body Steel Sheet (자동차용 강판 고속인장물성 데이터의 측정불확도 산출) 정세환  2012.12.10 17708