Forming limit for incremental stretching of aluminum and aluminum alloy blanks by single-tool-path process.
Forming limit for incremental stretching of aluminum and aluminum alloy blanks by single-tool-path process.
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单刀路工艺对铝及铝合金毛坯增量拉伸的成形极限
DOI：
10.2464/jilm.51.103
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
Hirofumi Fujino
中科院分区：
文献类型：
--
作者：
K. Kitazawa;Tamotsu Nishibayashi;Hirofumi Fujino
一个增量拉伸工艺与单一的工具路径的金属板材是有用的减少工具路径计划。然而，成形极限还没有充分揭示为单一的刀具路径过程。为了明确单一路径增量拉伸成形的极限，将铝及铝合金坯料拉伸成不同半顶角的截锥壳，并对其变形行为进行了研究。试验结果表明，成形极限取决于成形初期裂纹向周向扩展的起始位置。结果表明，模具速度、V值和坯料厚度对成形极限有较大影响。成形极限随着V的减小而增大，在Vm处达到最大值;当V低于Vm时，成形极限的减小是由低周疲劳效应引起的。虽然毛坯材料的化学成分对成形极限有显著影响，但毛坯材料的回火条件对成形极限没有影响。从正弦定律出发，实验结果表明，极限应变值是毛坯加工硬化指数的2 ~ 30倍。结果表明，增量拉伸的成形极限高于压力成形的成形极限。
An incremental stretching process with a single tool-path for sheet metals is useful for reduction of the tool-path schedule. However, the forming limit has not been revealed sufficiently for the single-tool-path process. In order to clarify the forming limit in the incremental stretching with a single tool-path, aluminum and aluminum alloy blanks are stretched to truncated conical shells with several values of half-apex angle, and the deformation behavior is examined. Experimental results show that forming limit is determined by the onset of cracking which propagates to circumferential direction in the early stage of the process. It is found that velocity of tool, V, and thickness of blank have major influences on the forming limit. The forming limit increases with decreasing V, and attains a maximum value at Vm; for V below Vm, a decrease in forming limit is caused by the low-cycle fatigue effect. Although the chemical composition of blank materials has a significant influence on the forming limit, the temper condition of blank materials has no influence on the forming limit. From considering of Sine law, experimental results show that the value of limiting strain is 2 to 30 times as high as that of work-hardening exponent of the blank. It is concluded that the forming limit of the incremental stretching is higher than that of press forming.