Coining Simulation of Commemorative Coins Based on Strain Gradient Plasticity Theory

Abstract

Abstract: To exactly describe the size effects caused by the fine patterns in coining simulation of commemorative coins， a constitutive equation was developed based on the Taylor dislocation model and the strain gradient plasticity theory.A nanoindentation test was conducted to obtain the mechanical properties of the Ag999 material， including the intrinsic material length and the nonlinear coupling relation between the statistically stored dislocation density and the geometrically necessary dislocation density.The proposed constitutive equation was applied to calculate the coining processes of a key-shaped coin， with the obtained coining force curves compared with the experimental ones.It is demonstrated that the proposed constitutive equation is capable of reflecting the size effects in coining and improves the accuracy in predicting coining forces.

Key words: commemorative coin, coining, Taylor dislocation model, strain gradient plasticity, size effect

摘要： 为了准确体现纪念币压印成形工艺中由于精细浮雕导致的尺寸效应，从Taylor位错模型出发，基于应变梯度塑性理论，建立了压印成形的本构方程。采用纳米压痕试验，获得了Ag999的材料内禀尺寸以及统计存储位错密度和几何必须位错密度的非线性耦合关系。将建立的本构方程用于计算某钥匙纪念币压印成形过程中的压印力变化曲线，并与试验结果进行对比，结果表明，建立的本构方程能够体现压印成形工艺中的尺寸效应，可有效改善压印力的预测精度。

关键词: 纪念币, 压印成形, Taylor位错模型, 应变梯度塑性, 尺寸效应

CLC Number:

TP391.9

YI Guofeng1;LI Qiaomin2;ZHONG Wen2;LIU Yuqi2. Coining Simulation of Commemorative Coins Based on Strain Gradient Plasticity Theory[J]. China Mechanical Engineering.

易国锋1;李巧敏2;钟文2;柳玉起2. 基于应变梯度塑性理论的纪念币压印成形数值模拟[J]. 中国机械工程.

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