저자명 박남수 
년도 2013 

Advanced high-strength steels (AHSS) for automotive applications generally exhibit an excellent combination of high strength and high formability resulting primarily from their high strain hardening capabilities. However, the material behavior of AHSS is still not fully identified and AHSS can show unpredictable and sudden failure as well as high and unpredictable spring back in sheet metal forming, which limits their usage in some applications. For the better application of the material, it is important to understand their plastic behavior and predict the onset of fracture in metals accurately. Especially in sheet metal forming, the anisotropy effect on the fracture strain should also be taken into consideration to consider the fracture behavior more properly since they show different mechanical properties resulting from their crystallographic structure and the characteristic of the rolling process.

The object of the study is to investigate the anisotropy effect of DP980 sheets on the fracture forming limit diagram (FFLD). In order to construct the FFLD, the history of equivalent plastic strain and strain path of the material point where the maximum equivalent plastic strain is observed just before the onset of fracture should be acquired at various loading paths. To utilize the data of various loading paths, three different types of tests are carried out to the facture including uniaxial tensile tests on classic dog-bone specimens, pure shear specimens and plane strain grooved specimens. Each specimen is made along three different orientations: the angle of 0˚ (rolling direction, RD); 45˚ (diagonal direction, DD); 90˚ (transverse direction, TD) with respect to the rolling direction of sheet metal to check the anisotropy effect on the fracture strain.

Strain measurements are performed using the 2-dimensional digital image correlation (DIC) system. DIC is an optical method which delivers whole-field noncontact measurement of strain providing the ability to accurately determine peak deformation as well as gradients over the entire area of interest. Fracture tests are carried out using Instron 5583 with dog-bone, pure shear and plane strain grooved specimen with deformation images captured by the high speed camera.

In order to reflect the influence of anisotropy on the fracture strain more, the Hill’48 yield function is applied to the Lou–Huh fracture model instead of von Mises yield function. And a modified Lou–Huh fracture model is represented in the space of strain path to use the experiment result directly. The history effect on the change of loading path, which should be considered for the damage accumulation in the material, is also applied to the modified Lou–Huh fracture model. Based on the measured data from the tests, modified Lou–Huh fracture loci are constructed and represented with respect to the loading direction. The loci are also transformed into the fracture forming limit diagrams which is of great importance in automotive applications.

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 1403
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 4599
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 4342
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 5060
45 Tensile Material Properties of Carbon/epoxy Composite Laminates at High Strain Rates (탄소섬유강화 복합재료의 변형률 속도에 따른 인장물성의 평가) 최재영  2013.02.12 7544
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 8183
» 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 6980
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 5937
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 8233
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 12069
39 Evaluation of Ultimate Buckling Strength of Stiffened Plates for Marine Structures (해양구조물용 보강판구조의 좌굴한계강도 평가) Waseem Gul  2010.07.13 8919
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 7941
37 Study on the Anisotropy of Auto-body Steel Sheets considering the Strain Rate(변형률속도를 고려한 차체강판의 이방성에 관한 연구) 이창수  2010.07.13 9172
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 7502
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 7410
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 6607
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 8024
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 8277
31 Finite Element Inverse Analysis of the Sheet Metal Forming Process Considering Bending History (굽힘 이력을 고려한 박판성형공정의 유한요소 역해석) 허지향  2008.01.25 6294
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 7104