Browse > Article

Microproperties and Fracture Behavior of Galvannealed Coating Layer of Automobiles  

Park, Chun-Dal (부산대학교 정밀기계공학과)
Ko, Dae-Cheol (부산대학교 동남권부품소재산학협력혁신연구소)
Kim, Byung-Min (부산대학교 정밀기계공학과)
Publication Information
Journal of the Korean Society for Precision Engineering / v.24, no.3, 2007 , pp. 91-99 More about this Journal
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
Galvannealed coating layer; Fracture behavior; Plastic deformation; Nano-indentation test; Flat friction test; Drawbead friction test; Micro-plasto hydrodynamic lubrication;
Citations & Related Records
연도 인용수 순위
  • Reference
1 Nunomura, Y. and Takasugi, T., 'Plastic Deformation and Fracture Behavior of Galvannealed Coating,' ISIJ International, Vol.43, No.3, pp.454-460, 2003   DOI
2 Ahn, J. H., 'Analysis and Development of Continuous Indentation Techniques for Evaluating Standard Tensile Flow Properties of Micromaterials,' Thesis of Seoul National University, 2001
3 Kim, Y. S., Nam, J. B. and Choi, W. J., 'A Study of Frictional Characteristics of Galvanized Sheet Steels for Automobiles,' Journal of the KSME, Vol. 14, No. 6, pp. 1474-1486, 1996
4 Hira, T., Yarita, I., Yasuda, A. and Abe, H. 'Frictional Behavior of Coated Steels in Sheet Forming,' Journal of the JSTP, Vol. 34, No. 393, pp. 1141-1146, 1993
5 Marder, A. R., 'The Metallurgy of Zinc-coated Steel,' Progress in Materials Science, Vol. 45, pp. 191-271, 2000   DOI   ScienceOn
6 Nakamura, S., Yoshida, A., Nishimoto, A. and Ono, T., 'Study on Method of Evaluation for Frictional Characteristics in Coated Steel Sheets,' IDDRG Working Group Meeting, 1990
7 Urai, M., Iwaya, J., Iwai, M. and Arimura, M., 'Effects of Press-forming Conditions and Coating Structure on Flaking Phenomenon in Galvannealed Steel Sheet,' Kobe Technical Report, Vol. 17, No.2, pp.29-32, 1997