Journal of the Korean Society for Precision Engineering (한국정밀공학회지)

Korean Society for Precision Engineering (한국정밀공학회)
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Microproperties and Fracture Behavior of Galvannealed Coating Layer of Automobiles

자동차용 합금화 용융아연도금강판의 도금층 미소물성 및 파괴 거동

  • 박춘달 (부산대학교 정밀기계공학과) ;
  • 고대철 (부산대학교 동남권부품소재산학협력혁신연구소) ;
  • 김병민 (부산대학교 정밀기계공학과)
  • Published : 2007.03.01
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Abstract

Fractures of galvannealed coating layer during actual press forming in automotive applications were observed by scanning electron microscopy in order to understand fracture mechanism. Fracture behaviors of galvannealed coating layer in extra deep drawing quality steels and high strength steels have been studied by performing the tests describing the representative plastic deformation in sheet metal forming such as uni-axial tensile test, compression test, bi-axial test and plane strain test. Growth and direction of cracks were deeply related to the plastic deformation modes and history. The material properties of galvannealed coating layer were investigated by nano-indentation test equipped with Berkovich diamond indentor for the specimens. Hardness and elastic modulus of the coating layer were higher than bared steels and that was the reason for crack of coating layer. Flat friction test and drawbead friction test were performed to observe the effect of the surface morphology on the frictional characteristics. The micro-plasto hydrodynamic lubrication were appeared and played an important role in reducing the coefficient of friction.

Keywords

References

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