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拔模具几何形状来影响作为生产扭杆弹簧的起始材料的钢丝，以使拉丝在横截面上拉伸压缩成形时形成的不同应力分布不会限制钢丝的成形性，从而可以通过剩余的残余应力来实现用传统生产的弹簧钢丝不能产生的弯曲半径。此外，通过调整钢丝的残余应力分布来提高扭杆弹簧的承载能力。为此，必须制定科学的基本原理，以便对拉拔模具的内部几何形状进行有针对性的设计，以便在拉拔钢丝的边缘区域产生压缩残余应力，这有利于部件生产，最重要的是，有利于应用中的后期加载行为。在第二个资助期，将根据第一阶段确定的工艺参数和“毕业图”的工艺限制来量化零部件的性能改善，并对模拟模型进行验证。通过对专门开发的拉丝试验装置的广泛研究，计划在考虑拉丝过程中的成形速度和温度的情况下，进一步优化具有新的拉拔模具几何形状的制件半成品上局部不同引入的宏观和微观残余应力。使用演示弹簧来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，已经开始的弯曲试验将继续进行模拟和实验。此外，还计划对钢丝产品和演示弹簧进行静态和动态载荷调查，以评估设定的残余应力状态以及在规定的振动周期(间隔)下产生的性能改善，并量化残余应力的稳定性。进一步发展用于分析织构材料状态下的微观结构和宏观和微观残余应力的测量和评估策略及其有效性，将使残余应力分布的分析得以扩展。通过建立材料模型进一步验证了有限元模拟的有效性，该材料模型描述了材料在成形过程中的相变，从而改善了性能预测。进一步的重点是分析和确定干扰变量与材料波动的相关性。其结果将是生产扭杆弹簧的创新工具和工艺概念，扭杆弹簧的特征是特定诱发的残余应力。

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.