Thermal loads of working coils in electromagnetic sheet metal forming
Thermal loads of working coils in electromagnetic sheet metal forming
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DOI：
10.1016/j.jmatprotec.2014.05.005
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发表时间：
2014-11
影响因子：
6.3
通讯作者：
S. Gies;C. Löbbe;C. Weddeling;A. Tekkaya
中科院分区：
文献类型：
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作者：
S. Gies;C. Löbbe;C. Weddeling;A. Tekkaya
电磁成形的一个基本问题是刀具寿命有限。此外，作用在工具线圈上的机械载荷，特别是热载荷影响其寿命。在电磁成形中，由于工作线圈中的焦耳加热，大约50%的部署电能损失。在大批量生产的情况下，这种热量的积累促进了线圈的故障，并减少了线圈的使用寿命。尽管热负荷如此重要，但关于盘管温度及其影响参数的信息不足。本文的重点是确定长期放电序列下的温度分布。利用红外摄像机进行了实验研究，测量了线圈表面温度。数值过程模拟用于收集工作线圈内部的温度信息。结果表明，在多次放电后，线圈达到了平衡温度。在分析的输入功率范围内，线圈最高表面温度和线圈最高绕组温度分别达到92℃和178℃。这些温度超过了大多数增强和绝缘材料的减弱温度。得到的影响线圈温度的参数的知识可用于改进工艺设计，以避免线圈的热过度应力。有和没有工件变形的实验的比较表明，在防止变形的情况下，温度总是较高的，因此，代表了线圈温度的上限。
One basic problem of electromagnetic forming is the limited tool life. Besides the mechanical loads especially thermal loads acting on the tool coil affect its lifetime. In electromagnetic forming, about 50% of the deployed electrical energy is lost because of joule heating in the working coil. In case of high volume production, an accumulation of this heat promotes failure of the coil and reduces the coil lifetime. Despite this importance of the thermal loads only insufficient information about the coil temperature and its influencing parameters is available. Focus of this paper is on the determination of the temperature distribution in case of long-term discharge sequences. Experimental investigations using an infrared camera were performed to measure the coil surface temperature. Numerical process simulation is used to gather information about the temperature inside the working coil. The results prove that the coil reaches an equilibrium temperature after several discharges. For the analyzed range of input power the maximum coil surface temperature and the maximum coil winding temperature reached values of 92 °C and 178 °C, respectively. These temperatures exceed the weakening temperature of most reinforcement and insulation materials. The derived knowledge about the parameters influencing the coil temperature can be used for an improved process design to avoid thermal overstressing of the coil. A comparison of experiments with and without workpiece deformation revealed that the temperature in case of prevented deformation is always higher, and thus, represents an upper bound for the coil temperature.