Abstract This paper presents application of two-step forming for improving the forming limit in rotary nosing with a relieved die. Nosing is one method which is used for reducing the diameter of a tube tip. “Two-step nosing” is composed of two stages and different dies are applied for the two stages. The die shapes are determined based on the occurrence tendency of defects in “one-step nosing”, where only one die is used through the whole process. In this research, a series of experiments and numerical analyses of one-step nosing was carried out for investigating the mechanism of the occurrence of defects. As a result, it is revealed that the occurrence of defects was highly relevant with the contact area between the die and tube. Based on the result of one-step nosing, the optimum die shapes were determined for the two stages, and then “two-step nosing” improved the forming limit 9% higher than one-step nosing under the optimum condition. Furthermore, “two-step nosing” was experimentally applied for forming eccentric nosed tubes, and its superiority was verified.

中文翻译：

---

两步成型提高轴对称和偏心鼻管制造用卸压模旋转鼻成形极限

摘要 本文介绍了两步成形技术在提高旋压模具成形极限中的应用。Nosing 是一种用于减小管尖直径的方法。“两步压头”由两个阶段组成，两个阶段采用不同的模具。模具形状是根据缺陷的发生趋势来确定的，在“一步鼻”中，整个过程只使用一个模具。在这项研究中，为了研究缺陷发生的机制，进行了一系列的一步鼻加工实验和数值分析。结果表明，缺陷的发生与模具和管子之间的接触面积高度相关。根据一步成型的结果，确定了两个阶段的最佳模具形状，然后“两步压鼻”在最佳条件下将成形极限比一步压鼻提高了9%。此外，实验性地应用了“两步压鼻”成型偏心鼻管，验证了其优越性。