金银纪念币多次压印成形机理及缺陷预测研究

Commemorative coins made of gold or silver are issued by the government as legal currency. The coins with fine surface qualities are powerfull emblems and regarded as cards of the country, which have great benefit to showcase the long history, modern development, and brilliant culture of China to the whole world..Multi-Coining is the main manufacture process of commemorative coins. Theoretical analysis and mechanism investigations of multi-coining process are lacked both home and abroad. The classical plasticity theory can not provide valid guidances to multi-coining either. In the research, size effect in the fine imprints will be considered to build precise elasto-plastic constitutive relations, friction model, and numerical fricion model in multi-coining process with gold and silver workpiece. Numerical simulation software for multi-coining process will be developed to provide valid solutions in coinage. The relationship between die cavities filling behavior in multi-coining and the key parameters such as feature size, fricional condition, coining force, and times will be investigated by experimental and numerical methods. The defect mechanism of flash line and shininess band will be revealed by experiments. Valid prediction criterions will be built to evaluate the flash line and shininess band defects in coining process. The research results will provide theoretical guidances to the design and developments of new commemorative coins, which will be beneficial to improve the qualities and reduce the costs of production.

金银纪念币是一个国家的法定货币。质量精美的纪念币，极具收藏价值和极强的象征性，起到传承历史，弘扬文化的作用，代表一个国家的文化名片，对于正在发展的中国来说可以更好地向世界展现自己。. 多次压印成形是金银纪念币主要成形工艺，但国际上缺少系统的成形理论和成形工艺研究，而且传统的塑性成形理论也不适合指导金银纪念币多次压印成形。因此项目通过考虑金银纪念币精细花纹的尺寸效应建立多次压印成形塑性本构理论、摩擦模型和精确的数值化模型，开发金银纪念币多次压印成形模拟系统。通过工艺实验和数值模拟方法研究摩擦、压印力和压印次数等工艺参数对多次压印成形材料塑性流动和充模规律的影响，以及对闪光线和光亮带等金银纪念币表面缺陷的影响，揭示多次压印成形机理，建立闪光线和光亮带的评估标准，准确预测金银纪念币压印成形缺陷。为金银纪念币设计和生产提供理论指导和成形数 .值模拟系统，提高产品质量，缩短生产周期。

针对现有纪念币设计与制造完全依赖传统经验，项目采用实验研究、理论分析与数值模拟相结合的手段，对金银纪念币的多次压印成形机理进行了研究。分析了纪念币压印成形中精细花纹模腔引起的尺寸效应，基于CMSG应变梯度塑性理论框架建立了纪念币压印成形的宏微观本构模型；深入研究了压印工艺的多次加卸载变形规律，发现了多次压印工艺的塑性变形机理；研究了金银纪念币闪光线和光亮带缺陷，通过实验和数值模拟方法发现了闪光线和光亮带缺陷产生机理；建立了摩擦数值模型和缺陷评估标准，成功开发了国内外第一款多次压印成形数值模拟软件COINFORM。本项目填补了国内外对金银纪念币多次压印成形以及压印成形缺陷研究方面的空白，克服了当前压印成形过分依赖设计经验的局限性，具有较强的理论价值和社会意义。