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
49 Structural Design and Evaluation for Improvement of the Roof Strength of a Three-Wheel Vehicle(삼륜차의 루프 강도 향상을 위한 구조 설계 및 평가) file Jesung Yoo  2017.06.07 107
48 Tension/Compression Hardening Behavior of Auto-body Steel Sheets at Intermediate Strain Rates Ranging from 0.1/s to 50/s(중 변형률속도 0.1/s ~ 50/s 영역에서의 차체 강판의 인장/압축 경화 거동에 관한 연구) 주근수  2014.01.16 3343
47 Tensile Properties of Nugget Region in a Spot Weld at Various Strain-Rates (점용접 너겟부의 변형률속도에 따른 인장 물성에 관한 연구) 박문수  2014.01.16 3012
46 Validation of Dynamic Hardening Models at High Strain Rates Using Taylor Impact Tests (테일러 충격시험을 이용한 고 변형률속도 조건에서의 동적 경화모델 검증) 박명준  2013.09.02 3894
45 Tensile Material Properties of Carbon/epoxy Composite Laminates at High Strain Rates (탄소섬유강화 복합재료의 변형률 속도에 따른 인장물성의 평가) 최재영  2013.02.12 6078
44 Design and Dynamic Simulation of a New Shock Absorbing Device with a Bending Strap in a Helicopter Pilot Seat (헬리콥터 조종석의 굽힘 판재를 이용한 새로운 충격흡수장치의 설계 및 동적 모사해석에 관한 연구) [1] 박주형  2013.02.12 6231
43 Anisotropy Effect on the Fracture Forming Limit Diagram of DP980 Sheets Considering the Loading Path (DP980 강판의 하중경로를 고려한 파단성형한계도에 미치는 이방성의 영향) 박남수  2013.02.12 5304
42 Study on the Dynamic Failure Model of Structural Adhesive Joints under Combined Loading Conditions(차량 구조용 접착제를 이용한 접합부의 복합하중조건에서 동적 파단 특성 연구) 임승찬  2013.01.24 4718
41 Study on the Strain-Rate Dependent Tensile Properties of Micro-Scale Aluminum Specimens(알루미늄 마이크로시편의 변형률속도에 따른 인장 특성 연구) 권준범  2012.03.01 7021
40 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 10738
39 Evaluation of Ultimate Buckling Strength of Stiffened Plates for Marine Structures (해양구조물용 보강판구조의 좌굴한계강도 평가) Waseem Gul  2010.07.13 7699
38 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 6536
» Study on the Anisotropy of Auto-body Steel Sheets considering the Strain Rate(변형률속도를 고려한 차체강판의 이방성에 관한 연구) 이창수  2010.07.13 7941
36 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 6298
35 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 6097
34 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 5387
33 Dynamic Material Properties of the Heat-Affected Zone (HAZ) in a Resistance Spot Weld(점용접 열영향부의 동적 물성특성에 관한 연구) 하지웅  2008.01.25 6866
32 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 6458
31 Finite Element Inverse Analysis of the Sheet Metal Forming Process Considering Bending History (굽힘 이력을 고려한 박판성형공정의 유한요소 역해석) 허지향  2008.01.25 5203
30 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 5857