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Springback compensation by stress superposition in forming of ultra high-strength steel sheets

超高强度钢板成形中的应力叠加回弹补偿

基本信息

批准号：
396455913
负责人：
Professor Dr.-Ing. Mathias Liewald
金额：
--
依托单位：
Institut für Umformtechnik (IFU)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2018
资助国家：
德国
起止时间：
2017-12-31 至 2020-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/396455913?language=en
关键词：
Springback compensation stress superposition forming

项目摘要

Today, the automotive industry is challenged by increasing environmental regulations as well as the continuous enhancement of the standard requirements regarding passengers safety. In order to achieve these requirements in car industry, the focus has been put on the reduction of car body weight through the use of lightweight materials as well as sheet metals with smaller thicknesses. Such tendencies lead to the increased use of ultra-high-strength steels (UHSS) for manufacturing of car body components. The structural car body components usually are manufactured by stretching or deep drawing. When the part is taken out of the die cavity after the forming process, a stress relaxation happens to reach a state of appropriate stress balance in the part. As a result of this stress relaxation, the springback or certain deviation between the formed part and the reference geometry occurs. Different kinds of springback can arise in this case: angle change, sidewall curl, radii change, and torsion or twisting. When forming car body structural parts from UHSS, an extremely high amount of springback can be expected. In state of the art exist some mechanically and geometrically based approaches which have shown certain possibilities for springback reduction. However, a methodology for springback compensation by parts manufactured from UHSS has not been developed until now.The motivation of this research results from the lack of such a methodology to compensate the springback when forming the parts from UHSS. For a successful development of such a kind of methodology for springback compensation, firstly, a dependency between the acting stresses after the forming and consequently caused part shape deviations or springback must be defined. The mentioned dependency should be described by a mathematical function. With the knowledge of this dependency between the stresses caused in the part and, therefore, occurred springback, a methodology for stress based springback compensation will be defined. Firstly, the compensation methodology to be developed will be based on dedicated stress superposition during the novel forming process with an alternating blank draw-in, and afterwards, if necessary, by changing the part cross-section size in certain part areas in the same tool. The required modification of the parts cross-sections will be provided by corresponding stretching without blank draw-in or by reduction of the drawing depth using back forming.

如今，汽车行业面临着越来越多的环境法规以及不断提高的乘客安全标准要求的挑战。为了实现汽车工业的这些要求，重点已经放在通过使用轻质材料以及厚度较小的金属板来减轻车身重量上。这种趋势导致超高强度钢（UHSS）在车身部件制造中的使用增加。车身结构部件通常通过拉伸或深冲压制造。当零件在成形过程后从模腔中取出时，应力松弛恰好达到零件中适当的应力平衡状态。由于这种应力松弛，在成形零件和参考几何形状之间发生回弹或一定的偏差。在这种情况下，可能会出现不同类型的回弹：角度变化、侧壁卷曲、半径变化以及扭转或扭曲。当用UHSS形成车身结构件时，可以预期极高的回弹量。在现有技术中，存在一些基于机械和几何的方法，这些方法已经显示出减少回弹的某些可能性。然而，回弹补偿的方法，由UHSS制造的零件还没有发展到现在。本研究的动机是缺乏这样的方法来补偿回弹时，形成UHSS零件。为了成功开发这种回弹补偿方法，首先必须确定成形后的作用应力与由此引起的零件形状偏差或回弹之间的相关性。所提到的依赖性应该通过数学函数来描述。通过了解零件中产生的应力与回弹之间的相关性，将定义一种基于应力的回弹补偿方法。首先，开发的补偿方法将基于在新的成形过程中使用交替的坯料拉入的专用应力叠加，然后，如果需要，通过改变相同工具中某些部分区域的零件横截面尺寸。通过相应的拉伸而不拉入毛坯或通过使用背面成形减少拉伸深度来提供所需的部件横截面修改。