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Research on the mechanism of flash line defect in coining

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Abstract

Flash line is one of the most important surface defects in coining process of silver commemorative coin. Due to the deficiency of study on the defect mechanism, it takes a long time to eliminate the defect through die tryouts which bring significant instabilities and development costs in coin manufacture. In the present investigation, the mechanism of flash line is studied by the elimination solutions and metal flow analysis using the finite element method (FEM). The radial components of friction in die–workpiece interface are considered as the main reasons of the defect. A modified friction model considering the influence of the sliding velocity in the die–workpiece interface is employed to describe the frictional behaviors in coining more properly. A novel radial friction work (RFW) model is proposed to predict the tendency of flash line and employed to a dynamic explicit FEM system for coining-COINFORM. The comparisons of the numerical and experimental results of a typical silver coin demonstrate that the RFW model is valid in the prediction of flash line.

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Authors and Affiliations

  1. State Key Laboratory of Material Processing and Die and Mould Technology, Huazhong University of Science and Technology, Wuhan, People’s Republic of China

    Wen Zhong & Yuqi Liu

  2. Shenyang Mint, Shenyang, People’s Republic of China

    Yunming Hu, Shengqiang Li & Maoming Lai

Authors
  1. Wen Zhong
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  2. Yuqi Liu
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  3. Yunming Hu
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  4. Shengqiang Li
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  5. Maoming Lai
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Correspondence to Yuqi Liu.

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Zhong, W., Liu, Y., Hu, Y. et al. Research on the mechanism of flash line defect in coining. Int J Adv Manuf Technol 63, 939–953 (2012). https://doi.org/10.1007/s00170-012-3952-3

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  • DOI: https://doi.org/10.1007/s00170-012-3952-3

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