A novel method to alleviate flash-line defects in coining process

► A variational constitutive model for a porous elasto-plastic material is used. ► The material flow inside the coin is conducted to study the flash lines. ► The radial friction work model is built on the coin surface to predict the flash-lines distribution. ► Good agreements are obtained by the two methods and experiment. ► A novel solution of redesigning the rim geometry is verified by the experiment.