저자명 이창수 
년도 2010 
The sheet metal forming is an effective process which is widely used in many industries. In sheet metal forming processes, the quality of deformed parts are influenced by many process parameters, such as the shape of the die, the shape and thickness of the initial blank, the material properties, the blank holding force, the friction, and so on. The main concern of many industries is to satisfy good formability at the high speed. The sheet metal forming process becomes simple and fast for the improvement of productivity. The deformation of steel sheets generally involves strain rate effects during the forming process. 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 the previous researches, it was demonstrated that material properties can be changed by the strain rate effect. However, the change of material properties has not been considered in the forming analysis since it is difficult to measure the change of the material properties with an experimental method. Among a number of material properties, especially, the r-value and the yield stress have a significant effect on the initial anisotropic state of auto-body steel sheets. The initial anisotropic state has an effect on the amount of spring-back since it calculates the different residual stress and strain distribution after the forming process. Hill48 quadratic yield criterion has been widely used for simulations of forming process of auto-body steel sheets due to the simplicity of its numerical formula and the low computing cost. It shows good performance to approximate anisotropy of auto-body steel sheets. This paper deals with the anisotropic material properties and the initial yield state considering the strain rate. Specimens of SPCC and DP590 were extracted at interval of 15o from 0o(RD; rolling direction) to 90o(TD; transverse direction). Uniaxial tensile tests were performed according to the strain rate and the loading angle from RD to TD in order to obtain flow stress curves and tensile properties. The r-values were measured with high speed camera by analyzing the deformation history during the tensile test. To obtain reliable r-values, the measuring range is limited to the necking instability strain of steel sheets. Anisotropy of auto-body steel sheets is described by using Hill48 and Yld89(Barlat89) yield functions according to the strain rates ranged from 0.001/sec to 100/sec. Hill48 and Yld89 yield loci of auto-body steel sheets with respect to the strain rate are constructed in order to visualize initial yield state. The performance of two yield criteria is evaluated by comparing yield loci constructed in the principal stress plane. It shows that the initial yield states are different when the strain rate is considered to describe anisotropy of steel sheets. Anisotropic yield function is modified to describe anisotropic yield state of steel sheets according to the strain rate effectively by approximating r-value and yield stress with respect to the strain rate.  
번호 제목 저자명 날짜 조회 수
29 Optimization of the roller levelling process for Al7001 T9 pipes with the Finite Element Method and Taguchi Method(유한요소법과 다구찌 방법을 이용한 Al 7001 T9 파이프의 롤러교정 공정 최적화) 허진혁  2005.11.29 14621
28 Tension Test and Specimen Design with the Finite Element Method at Intermediate Strain Rates(준고속 변형률 속도에서의 인장실험 및 유한요소법을 이용한 박판 인장시편의 형상결정) 송정한  2005.11.29 4654
27 Elastic-plastic Finite Element Analysis of Drawbead Forming and Drawing Processes for Equivalent Boundary Conditions in Sheet Metal Forming(드로우비드 성형과 드로잉 공정의 탄소성 유한요소 해석 및 박판 성형공정에서의 등가 경계조건) [1] 박종세  2005.11.29 6515
26 Efficiency enhancement of sheet metal forming analysis with a mesh regularization method (격자 정방형화 방법을 이용한 박판 성형해석의 효율개선) 윤종헌  2005.11.29 4791
25 Adaptive Time-stepping Procedure for Dynamic Limit Analysis (동적 극한해석을 위한 적응적 시간간격기법) 이종섭  2005.11.29 4656
24 Design optimization of auto-body members for crashworthiness enhancement with the response surface method (반응표면법을 이용한 차체 부재의 충돌성능 향상을 위한 설계 최적화) 나승렬  2005.11.29 5587
23 Study on the characterization of the dynamic material properties of sheet metal for auto-body considering the pre-strain effect(예비변형률 효과를 고려한 차체용 박판의 동적 물성 특성 연구) 김석봉  2005.11.29 5287
22 The crashworthiness evaluation of asymmetric hat-type rectangular tube by static and dynamic crush tests (동적 압궤 실험을 통한 충돌 성능 평가 ) 김진성  2005.11.29 8437
21 Dynamic Tensile Tests of Auto-body Steel Sheets with the Variation of Temperature for Material Constitutive Equations (차체용 강판의 온도에 따른 동적 인장시험 및 물성 구성방정식에 관한 연구) [1] 이희종  2006.03.07 5706
20 Study on the 3-D finite element modeling of fiber reinforced rubber composite using the rebar element (리바요소를 이용한 섬유강화 고무기저 복합재료의 3차원 유한요소 모델링기법 연구) 정세환  2006.08.18 7183
19 Finite Element Inverse Analysis of the Sheet Metal Forming Process Considering Bending History (굽힘 이력을 고려한 박판성형공정의 유한요소 역해석) 허지향  2008.01.25 6363
18 Cross-section Shape Design of an Aluminum Crash Box for Crashworthiness Enhancement (충돌성능 향상을 위한 알루미늄 크래쉬 박스의 단면 형상 설계) [1] 이경호  2008.01.25 8406
17 Dynamic Material Properties of the Heat-Affected Zone (HAZ) in a Resistance Spot Weld(점용접 열영향부의 동적 물성특성에 관한 연구) 하지웅  2008.01.25 8107
16 Study on the Crash Energy Absorption and Dynamic Local Buckling of the Expansion Tubes (확관튜브의 충돌에너지 흡수성능 및 동적 국부좌굴에 관한 연구) 안광현  2008.01.28 6691
15 Upper Bound Analysis of Dynamic Buckling Phenomenon of Circular Tubes Considering Strain Rate Effect (변형률 속도를 고려한 원형 튜브의 동적 좌굴 현상의 상계 해석에 관한 연구) 박충희  2008.08.02 7508
14 Reliability Based Design Optimization for Crashworthiness of a Spot Welded Hat Type Member (점용접 모자형 사각관의 충돌성능에 대한 신뢰도 기반 최적설계) 김유종  2010.07.13 7591
» Study on the Anisotropy of Auto-body Steel Sheets considering the Strain Rate(변형률속도를 고려한 차체강판의 이방성에 관한 연구) 이창수  2010.07.13 9243
12 Study on Design of Stress Wave Micro Sensor for High Speed Transportation Safety System (고속운송기구의 안전시스템을 위한 마이크로 응력파 센서 설계 연구) 임성준  2010.07.13 8041
11 Evaluation of Ultimate Buckling Strength of Stiffened Plates for Marine Structures (해양구조물용 보강판구조의 좌굴한계강도 평가) Waseem Gul  2010.07.13 8998
10 Study on the Fracture Strain of DP780 Sheets Considering the Strain Rate and Loading Path (변형률속도와 하중경로를 고려한 DP780 강재의 파단변형률에 관한 연구) 박근환  2012.02.20 12172