To understand the mechanism and metal flow during the minting process of a silver coin, the material properties and the coining interface friction conditions were investigated. The ring compression test was conducted to evaluate the friction behaviour of the coining process. The changes in the dimensions of the internal diameter of compressed rings provide a particularly sensitive means for friction evaluation. Standard rings made of fine silver were tested. To calibrate the experimental results, a twodimensional axisymmetric FEM simulations of ring compression test were carried out. The fine silver material properties obtained from the standard tensile tests and a two-parameter friction model were used in the FEM simulations. The two-parameter friction model used combines the Coulomb friction model and the friction factor yield stress model. Through carefully measuring the geometrical changes of the ring, the calibration curves were obtained for different friction conditions. The parameters in the friction model for fine silver coining process were successfully obtained by calibrating the experimental results.

Additional Metadata
Keywords Coining process, Finite element analysis, Friction conditions, Ring test
Journal Steel Research International
Citation
Guo, K. (Kai), Wang, X, Bell, R. (Robert), Li, X. (Xianyao), & Papais, S. (Steve). (2008). The experimental evaluation of friction conditions during a silver coining process. In Steel Research International (Vol. 79, pp. 80–87).