Generating residual compressive stresses in wire drawing for manufacturing highly-stressed torsion springs (DruDraZie)

该项目的目的是通过使用特别修改的拉伸模具几何形状来影响作为扭杆弹簧生产的起始材料的线材，使得在拉伸压缩成形期间通过线材拉伸在横截面上形成的不同应力分布不会限制线材的可成形性，并且弯曲半径不能用常规生产的弹簧线材产生，因此可以通过剩余的残余应力来实现。此外，扭杆弹簧的负载能力将通过调整线材的残余应力分布来提高。为此，必须制定科学的基本原理，以便有针对性地设计拉丝模的内部几何形状，从而在拉丝的边缘区域中产生压缩残余应力，这对于部件生产是有利的，尤其是对于应用中的后续加载行为是有利的。在第二个供资期，将根据第一阶段确定的工艺参数和“毕业图”的工艺限值，对部件的性能改进进行量化，并验证模拟模型。通过对专门开发的拉丝测试设备进行广泛的研究，计划进一步优化制造的半成品上部分不同的宏观和微观残余应力，并采用新的多次拉拔模具几何形状，同时考虑到拉丝过程中的成形速度和温度。演示弹簧用于评估弯曲过程和残余应力之间的相互作用，以设置最适合应用的残余应力状态。为此，将继续模拟和实验性地进行已经开始的弯曲试验。此外，还计划对线材产品和演示弹簧进行静态和动态载荷研究，以评估设定的残余应力状态以及在规定的振动周期（间隔）下性能的改善，并量化残余应力的稳定性。进一步发展的测量和评估策略的微观结构和宏观和微观残余应力的织构材料状态的分析和验证将允许分析的残余应力分布的扩展。有限元模拟进一步验证了材料模型的发展，它代表了材料在成形过程中的相变，从而提高了性能的波动。进一步的重点是分析和确定干扰变量和物质波动的相关性。其结果将是一种用于扭杆弹簧生产的创新工具和工艺概念，其特征在于特定的诱导残余应力。

The aim of the project is to influence wire as a starting material for the production of torsion bar springs with the use of specifically modified drawing die geometries in such a way that the different stress distributions formed during the tensile compression forming by wire drawing over the cross-section do not limit the formability of the wire and that bending radii, which cannot be produced with conventionally produced spring wires, can thus be achieved by the remaining residual stresses. Furthermore, the load capacity of the torsion bar springs is to be improved by the adjusted residual stress distribution of the wire. For this purpose, scientific fundamentals have to be worked out so that a targeted design of the internal geometry of the drawing die induces compressive residual stresses in the edge area of the drawn wire, which are advantageous for the component production and, above all, for the later loading behaviour in the application. In the second funding period, the property improvements of the components will be quantified on the basis of the process parameters determined and the process limits for "graduation drawing" from the first phase, and the simulation models will be validated. By means of extensively investigations on the specially developed test facility for wire drawing, it is planned to further optimize the partially differently introduced macro and micro residual stresses on the manufactured semi-finished products with new drawing die geometries for multiple drawing, taking into account the forming speed and temperature during wire drawing. A demonstrator spring is used to evaluate the interaction between the bending process and residual stresses in order to set the residual stress state optimized for the application. For this purpose, the bending tests already started will be continued simulatively and experimentally. In addition, static and dynamic load investigations on the wire products and demonstrator springs are planned in order to evaluate the set residual stress states and the resulting improvement in properties at defined vibration cycles (intervals) and to quantify the stability of the residual stresses. The further development of the measurement and evaluation strategies for the analysis of the microstructure and the macro and micro residual stresses in textured material states and their validation will allow the analysis of the residual stress distribution to be extended. The FE simulations are further validated by the development of a material model, which represents the phase transformation of the material during the forming process and thus improves the property prognoses. Further focal points are the analysis and determination of the relevance of disturbance variables and material fluctuations. The result will be an innovative tool and process concept for the production of torsion bar springs, which are characterized by specifically induced residual stresses.