Experimental characterisation and numerical analysis of increasing fatigue strength by residual stresses for cross rolling parts

通过残余应力提高交叉滚压零件疲劳强度的实验表征和数值分析

• 批准号: 374767659
• 负责人: Professor Dr.-Ing. Alexander Brosius
• 金额: --
• 依托单位: Professur für Formgebende Fertigungsverfahren
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/374767659?language=en
• 关键词: Experimental; characterisation; numerical; analysis; increasing

Within the framework of SPP 2013, research is being conducted into the use of residual stresses induced by forming technology to improve component properties. The aim of the proposed project is the targeted setting of residual stress states in cold forming processes to increase fatigue strength. The project is focused on a hybrid component in which the shaft and hub are joined by a transverse rolling process. This results in a process-related circumferential notch which can have an unfavourable effect on the expected service life. This disadvantage can be compensated by selectively inducing residual compressive stresses in the notch during the rolling process.In the first two funding periods, a stable process was established and the performance of the approach for improving fatigue strength was demonstrated. Within this context, different numerical models were developed to simulate the process and fatigue life. The ability to positively influence the service life through different process variants was demonstrated.In the third and final funding period, the focus is now on the real component, taking into account the influence of a joining partner (hub) under service conditions. For this purpose, the focus will be on the methodical component and process design with regard to the residual stress states to be set in the notch and the joining zone. For practical implementation, a very flexible rolling jig is being set up which also allows complex process variants with a greater variety of geometries in order to meet the requirements for the desired residual stresses profiles.Furthermore, the fatigue behaviour of the component is again considered and gains in importance due to the application to real components under operating conditions. The stability of the compressive residual stresses in the failure-relevant notch and at the joint is critical for the service life. Therefore, the change in residual stresses under cyclic load is measured and simulated by means of an elastic-plastic model. The crack propagation model will be extended to the 3D case and thus, as part of a coherent simulation strategy, the fatigue life of the components will be analysed taking into account the variable residual stresses.At the end of the third funding period, the rolled component will be specifically designable with respect to its joint connection and notch geometry by means of a transferable design methodology. The fatigue strength was analysed under consideration of the residual stress stability and the findings on the residual stress changes were included in the design methodology. The flexible new process kinematic will enable the residual stresses in the notch and the joining zone to be set independently, and long-term tests on real components will provide proof of the overall approach. In addition, transferable statements on residual stress stability in solid components will be available.

在SPP 2013的框架内，正在研究利用成形技术引起的残余应力来改善部件性能。该项目的目的是在冷成型过程中有针对性地设置残余应力状态，以提高疲劳强度。该项目的重点是一个混合动力部件，其中轴和轮毂通过横向轧制工艺连接。这导致与工艺相关的周向缺口，这可能对预期使用寿命产生不利影响。这一缺点可以通过在轧制过程中在缺口中选择性地诱导残余压应力来补偿。在前两个资助期，建立了稳定的工艺，并证明了该方法用于提高疲劳强度的性能。在此背景下，开发了不同的数值模型来模拟过程和疲劳寿命。在第三个也是最后一个供资期，重点是真实的部件，同时考虑到在使用条件下加入合作伙伴（枢纽）的影响。为此，重点将放在有条理的组件和工艺设计方面的残余应力状态，以设置在缺口和连接区。为了实际应用，我们设计了一种非常灵活的轧制夹具，该夹具还允许复杂的工艺变化，具有更多的几何形状，以满足对所需残余应力分布的要求。此外，由于在运行条件下应用于真实的部件，部件的疲劳特性再次被考虑并变得更加重要。失效相关缺口和接头处残余压应力的稳定性对使用寿命至关重要。因此，在循环载荷下的残余应力的变化进行了测量和模拟的弹塑性模型。裂纹扩展模型将扩展到三维情况，因此，作为连贯模拟战略的一部分，将在考虑可变残余应力的情况下分析部件的疲劳寿命。在第三个供资期结束时，将通过可转移的设计方法，对轧制部件的接头连接和缺口几何形状进行专门设计。在考虑残余应力稳定性的情况下分析疲劳强度，并将残余应力变化的结果纳入设计方法中。灵活的新工艺运动学将使缺口和连接区域的残余应力能够独立设置，并且对真实的部件的长期测试将为整体方法提供证据。此外，还将提供关于固体部件中残余应力稳定性的可转移声明。