Development of a model to describe springback and residual stresses resulting from bending at elevated temperatures

开发模型来描述高温弯曲产生的回弹和残余应力

基本信息

批准号：
283169793
负责人：
Professor Dr.-Ing. A. Erman Tekkaya
金额：
--
依托单位：
Institut für Umformtechnik und Leichtbau (IUL)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2016
资助国家：
德国
起止时间：
2015-12-31 至 2018-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/283169793?language=en
关键词：
Development model describe springback residual

项目摘要

For the steady weight reduction of bent parts by the application of lightweight metals with increasing strength, new challenges arise to keep dimensional accuracy and to deal with the decreased formability in conventional forming processes as the fast clocked progressive dies. Bending at elevated temperatures through inductive heating in progressive dies represents an innovative solution to produce high accuracy and complex bent parts in a large scale despite of the limited formability due to the higher strength. Hence, the aim of the project is the prediction of springback and residual stresses for bending at elevated temperatures, during which numerous temperature and time dependent influences can occur. In this context, temperature and time dependent, physical mechanisms with a relevant effect on the springback and the stress state will be characterized in hot tensile tests and further bending tests. The experimental results serve further to model the produced geometry as well as the residual stresses through an analytical or a semi-analytical approach. The focus will be on creep strains during forming and loaded holding, the plastic flow during quenching with an active load, and the variable Youngs modulus in a cold and a hot state. The mechanism will be investigated through warm tensile tests and a parameter analysis. Subsequently, the modeling will be supported by bending tests with cooled and also tempered tools. The approach will be verified further with numerical simulations. Finally, the deduced correlation gives an analytical comprehension of the product properties as the bending angle and the residual stresses in relation to process temperatures, times, and the strain rate.

为了通过应用强度不断增加的轻质金属来稳定地减轻弯曲零件的重量，需要保持尺寸精度并应对传统成形工艺（如快速时钟级进模）中成形性下降的问题。通过级进模具中的感应加热在高温下弯曲代表了一种创新的解决方案，可大规模生产高精度和复杂的弯曲零件，尽管由于强度较高而导致可成形性有限。因此，该项目的目的是预测高温下弯曲的回弹和残余应力，在此期间可能会发生许多与温度和时间相关的影响。在这种情况下，对回弹和应力状态具有相关影响的温度和时间相关的物理机制将在热拉伸试验和进一步的弯曲试验中进行表征。实验结果进一步通过分析或半分析方法对产生的几何形状以及残余应力进行建模。重点是成形和负载保持期间的蠕变应变、主动负载淬火期间的塑性流动以及冷态和热态下的可变杨氏模量。该机制将通过热拉伸试验和参数分析进行研究。随后，将通过使用冷却和回火工具的弯曲测试来支持建模。该方法将通过数值模拟进一步得到验证。最后，推导出的相关性给出了产品特性的分析理解，即弯曲角度和残余应力与工艺温度、时间和应变率的关系。