저자명 허지향 
년도 2013 
A proper description of anisotropy is one of the most important aspects in the simulation of the sheet metal forming process since sheet metals generally exhibit a significant anisotropy of the mechanical properties due to their crystallographic structure and the characteristics of the rolling process. Many researchers, hence, have been proposed diverse anisotropic yield criteria to model the anisotropic yield behavior of sheet metals.
The deformation of steel sheets generally involves strain rate effects during the forming processe.  When the deformation of steel sheets is accelerated, the strain rate effect becomes significant. Therefore, it is essential to calculate the final shape and deformation history of a product considering the strain rate effect in the forming process. In previous research works, it was demonstrated that the stress-strain relationship of metals are highly influenced by the strain rate. However, there have been few studies on the effect of strain-rate on the anisotropic yield behavior of materials.
This study deals with the modeling of strain-rate dependent anisotropy yield criteria of auto-body steel sheets including two advanced high strength steel (AHSS) sheets of TRIP590 and DP780 and a conventional cold-rolled steel sheet of SPCC. Uniaxial tensile tests were performed at different strain rates varying the loading angle from the rolling direction to investigate the effect of the strain rate on the anisotropy of material properties by obtaining yield stresses and r-values. A new method was proposed to measure the r-value at intermediate strain rates with the aid of digital image correlation (DIC). Anisotropic yield behavior of auto-body steel sheets was modeled with the Hill48, Yld89 and Yld2000-2d yield criteria at strain rates ranging from 0.001/s to 100/s. The performance of the three yield criteria was evaluated by comparisons of theoretically calculated planar distributions of the uniaxial yield stress and the r-value with experimental data. Yld2000-2d yield criterion was found to accurately describe the anisotropic yield behavior of the AHSS sheets since it has great flexibility due to the larger number of the mechanical parameters incorporated than that of Hill48 yield criterion with which the anisotropy of SPCC can be described acceptably. Yld2000-2d and Hill48 yield loci are constructed for AHSS and SPCC, respectively, in order to investigate the effect of the strain rate on the anisotropic yield behavior at the given range of strain rates. For the materials investigated, it is evident that strain rate has a distinct effect both on the shape and magnitude of the yield surface, and the plastic anisotropy tends to diminish at a higher strain rate. New yield criteria were proposed to describe the change of the anisotropic yield behavior with the strain rate by expressing the anisotropic coefficients of Hill48 and Yld2000-2d yield criteria as a function of the strain rate. A new stress update algorithm was developed for the proposed yield criteria based on the consistency method. The new algorithm was implemented in finite element analysis with a commercial software, Abaqus/Explicit User subroutine (VUMAT).
Finite element analyses of cylindrical cup drawing processes were carried out with and without considering the change of plastic anisotropy with the strain rate. The comparisons show that the the change in plastic anisotropy results in a significant change in the earing profile, stress distribution and thickness distribution.
번호 제목 저자명 날짜 조회 수
27 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 27147
26 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 23001
25 A New Ductile Fracture Criterion for the Formability Prediction of Steel Sheets and Its Application to Finite Element Analysis (강판의 성형성 예측을 위한 새로운 연성 파괴 조건 및 유한 요소 해석에의 응용) [1] Yanshan Lou  2012.12.10 22991
24 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 22990
23 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 22257
22 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 21751
21 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 20445
20 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 20284
19 Optimum Process Design in Sheet Metal Forming Processes using Finite Element Sensitivity Analysis (유한요소 민감도해석을 이용한 박판금속성형에서의 공정변수 최적설계) [1] 김세호  2005.11.29 20099
» Strain-Rate Dependent Anisotropic Yield Criteria for Auto-body Steel Sheets (자동차용 강판의 변형률속도 의존 이방성 항복함수에 관한 연구) 허지향  2012.12.11 19815
17 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 19217
16 Measurement Uncertainty Evaluation for High Strain Rate Tensile Properties of Auto-body Steel Sheet (자동차용 강판 고속인장물성 데이터의 측정불확도 산출) 정세환  2012.12.10 19135
15 Dynamic Formulation of Finite Element Limit Analysis for Impact Simulation of Structural Members (구조부재의 충돌해석을 위한 유한요소 극한해석의 동적 수식화) 김기풍  2005.11.29 19033
14 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 19031
13 Rate Dependent Hardening Model for Pure Titanium Considering the Effect of Deformation Twinning (쌍정의 영향을 고려한 티타늄의 변형률속도 의존 경화 모델) 안광현  2012.12.12 18792
12 Microscopic investigation of the strain rate hardening for auto-body steel sheet(차체강판 변형률속도 경화의 미시적 관찰) 윤종헌  2010.07.13 18408
11 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 18296
10 Crash Analysis of Auto-body Structures with an Explicit Finite Element Method ( 외연적 유한요소법을 이용한 차체 구조물의 충돌해석 ) 강우종  2005.11.29 17968
9 Shell Element Formulation for Limit Analysis of Thin-Walled Structures ( 박판부재의 붕괴거동해석을 위한 극한해석의 쉘요소 수식화 ) 김현섭  2005.11.29 16087
8 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 15980