Factors governing hole expansion ratio of steel sheets with smooth sheared edge

• Published in: Metals and materials international Vol. 22; no. 6; pp. 1009 - 1014
• Main Authors: Yoon, Jae Ik, Jung, Jaimyun, Lee, Hak Hyeon, Kim, Gyo-Sung, Kim, Hyoung Seop
• Format: Journal Article
• Language: English
• Published: Seoul The Korean Institute of Metals and Materials 01.11.2016; Springer Nature B.V; 대한금속·재료학회
• Subjects: Automotive components; Automotive materials; Characterization and Evaluation of Materials; Chemistry and Materials Science; Cracks; Damage accumulation; Damage assessment; Elongation; Engineering Thermodynamics; Heat and Mass Transfer; High strength steels; Machines; Magnetic Materials; Magnetism; Manufacturing; Materials Science; Mechanical properties; Metal forming; Metal sheets; Metallic Materials; Processes; Punching; Shearing; Sheet metal; Solid Mechanics; Steel; Steels; Strain rate sensitivity; Tensile properties; Tensile tests; 재료공학; metals; deformation; tensile test; stretch-flangeability; mechanical properties
• ISSN: 1598-9623; 2005-4149
• DOI: 10.1007/s12540-016-6346-5

Stretch-flangeability measured using hole expansion test (HET) represents the ability of a material to form into a complex shaped component. Despite its importance in automotive applications of advanced high strength steels, stretch-flangeability is a less known sheet metal forming property. In this paper, we investigate the factors governing hole expansion ratio (HER) by means of tensile test and HET. We correlate a wide range of tensile properties with HERs of steel sheet specimens because the stress state in the hole edge region during the HET is almost the same as that of the uniaxial tensile test. In order to evaluate an intrinsic HER of steel sheet specimens, the initial hole of the HET specimen is produced using a milling process after punching, which can remove accumulated shearing damage and micro-void in the hole edge region that is present when using the standard HER evaluation method. It was found that the intrinsic HER of steel sheet specimens was proportional to the strain rate sensitivity exponent and post uniform elongation.