Key factors of stretch-flangeability of sheet materials

Yoon, Jae Ik; Jung, Jaimyun; Kim, Jung Gi; Sohn, Seok Su; Lee, Sung Hak; Kim, Hyoung Seop

doi:10.1007/s10853-017-1012-y

Cited by 43 publications

(15 citation statements)

References 48 publications

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“…The punching process causes strain hardening and formation of microvoids and microcracks at the edge of the hole acting as stress concentration sites and leading to fracture. Therefore, the evaluation of HER involves analysis of the stretch‐flangeability with initial defects and strain hardening close to the hole edge …”

Section: Resultsmentioning

confidence: 99%

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Microstructure, Crystallographic Texture, and Stretch‐Flangeability of Hot‐Rolled Multiphase Steel

Moura

Ferreira

Martins

et al. 2020

steel research int.

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The microstructure, crystallographic texture, strain hardening in the hole edge‐punched and stretch‐flangeability of hot‐rolled multiphase sheet steel is investigated by scanning electron microscopy, electron backscatter diffraction, and microhardness measurements. The results show that the strain hardening in the hole edge‐punched is not the main factor that influences the hole expansion ratio. The bainite fraction, average grain area, and kernel average misorientation distribution mean are microstructure factors that improve the hole expandability and reduce the effect of strain hardening in the hole edge‐punched on the hole expansion ratio. The crystallographic texture affects the hole expandability. The high intensity of {332}<113>α and {111}<112>α components that have higher normal anisotropy (rtrue¯) also reduces the effect of strain hardening at the hole edge‐punched. The cracks propagate through the interfaces following the banded microstructure direction at the hole edge‐punched during the punching process. The gamma distribution analysis of the kernel average misorientation distribution indicates that there are different energy transfer (β parameter) and dislocation densities due to different cooling rates.

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Section: Resultsmentioning

confidence: 99%

“…The punching process shows a lower HER compared to machining and wire cutting as a result of strain hardening and formation of microvoids and microcracks at the hole edge . Microvoid nucleation occurs at the ferrite/martensite interfaces and through martensite cracking .…”

Section: Introductionmentioning

confidence: 99%

Microstructure, Crystallographic Texture, and Stretch‐Flangeability of Hot‐Rolled Multiphase Steel

Moura

Ferreira

Martins

et al. 2020

steel research int.

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“…Negligible number of defects are present at the central hole edge which is machined by EDM technique. [16][17][18][19]21,25 HER for DP and ferritic steel sheets are 110% and 152% for EDM-machined hole, respectively (Figure 4). The uniform elongation of DP and ferritic steel sheets are 17.5% and 26%, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…16–19 For the same reason, researchers recently established correlation between HER and fracture toughness. 17,18,20,21…”

Section: Introductionmentioning

confidence: 99%

“…[16][17][18][19] For the same reason, researchers recently established correlation between HER and fracture toughness. 17,18,20,21 Many researchers reported the correlations between the tensile properties and HER of specific steel groups, [22][23][24][25][26][27][28][29][30][31] but the relationships are not universal and not derived from the fundamental of deformation process. Researchers also reported the relationship between the micro-structural features of material and the HER, 3,30,31 but limited to similar steel grades.…”

Section: Introductionmentioning

confidence: 99%

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Fundamental aspect of stretch-flangeability of sheet metals

Paul

2018

Proceedings of the Institution of Mechanical Engineers, Part B:

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Stretch-flangeability of sheet metal is normally represented by hole expansion ratio. Hole expansion ratio cannot be determined from uniaxial tensile test though uniaxial tensile deformation occurs at the hole’s edge, because of fundamental difference in deformation and damage processes present between hole expansion test and uniaxial tensile test. It is proposed that only localized necking is observed in hole expansion test; however, diffuse necking followed by localized necking is observed in uniaxial tensile test of sheet metal. It is noticed that the hole expansion ratio is marginally higher than maximum diffuse neck strain determined from uniaxial tensile test with local strain measurement by digital image correlation technique. The absence of diffuse neck in hole expansion test with defect-free central hole (i.e. electrical discharge machined hole) results far higher hole expansion ratio than uniform elongation of the material.

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