Targeted creation of residual stresses by forming of local structures in sheet thickness direction via an embossing process to improve component performance

该研究项目的总体目标是开发一种成形工艺路线，以有针对性地产生薄壁金属板件的残余应力（RS）。成形诱导RS旨在提高主要承受动态载荷的金属板制成的结构部件的疲劳强度。在项目范围内，在I.和二.通过结合成形和压花工艺，可以在薄壁金属板部件中产生压缩残余应力，这可持续地增加部件的循环操作强度。该研究项目的一个特别重点是粗复相材料（X2CrNiN-23 - 4双相钢）的成形。特别是，将系统地评价特定阶段的微型遥感的贡献。在这种情况下，一方面，测量和评价战略，当地的RS分析开发的材料分析领域。另一方面，基于机理的遥感建模，二.和三.类通过数值有效的平均场方法提供了双尺度模拟的RS在两相微观结构的可能性。这些实验和数值研究的结果最终导致薄壁结构部件的组合制造工艺的发展，其中通过将成形操作与同时压花和随后的再成形相结合，以有针对性的方式诱导压缩RS。这些局部RS抵消了部件运行时作用的拉伸载荷应力。第三个资助期的目的是将前两个资助期获得的关于RS的生成、分析、稳定性和模拟的知识转移到循环加载的真实的部件上，特别是抽象的承载板上。这包括工具概念的整体数字设计及其制造实施。考虑了资助期I和II中开发的测量、评估和模拟策略，以最准确地确定所有尺度上载板中诱导的RS（I.至III. kind）。对于所有规模的RS模拟和实验分析，即将到来的资助期的重点将是晶体学纹理。除了考虑板厚方向的织构梯度外，还将通过数值和实验研究变形驱动织构演化的影响。该项目中开发的RS模拟和分析方法将在所有尺度上进行验证，并在跨项目基准中进行应用。该研究项目是在2013年优先计划征集框架内，由IFU，斯图加特大学，IAM-WK和卡尔斯鲁厄理工学院（KIT）的ITM-KM共同开展的。

The general objective of the research project is to develop a forming process route for the targeted generation of residual stresses (RS) into thin-walled sheet metal components. The forming-induced RS is intended to improve the fatigue strength of structural components made of sheet metal that are predominantly subjected to dynamic loads. Within the scope of the project, it was demonstrated during the I. and II. funding period that by combining a form-ing and embossing process, compressive residual stresses can be generated in a thin-walled sheet metal component, which sustainably increase the cyclic operational strength of the component. A particular focus of this research project will be on the forming of coarse multiphase materi-als (duplex steel X2CrNiN-23-4). In particular, the contribution of phase-specific micro-RS will be systematically evaluated. In this context, on the one hand, measurement and evaluation strategies for local RS analyses are developed in the field of materials analysis. On the other hand, the mechanism-based modeling of RS of the I., II. and III. kind by means of numerically efficient mean-field approaches offers the possibility of two-scale modeling of RS in two-phase microstructures. The findings from these experimental and numerical investigations finally lead to the development of a combined manufacturing process for a thin-walled struc-tural component, into which compression RS are induced in a targeted manner by combining a forming operation with simultaneous embossing and subsequent reforming. These local RS counteract the tensile load stresses that act when the components are in operation.The aim of funding period III is to transfer the knowledge gained in the previous two funding periods with regard to the generation, analysis, stability and simulation of RS onto a cyclically loaded real component, in particular an abstracted carrier plate. This includes the holistic nu-merical design of the tool concept and its manufacturing implementation. The measurement, evaluation and simulation strategies developed in funding periods I and II are considered with regard to the most exact possible determination of the induced RS in the carrier plate on all scales (I. to III. kind). For the simulation and experimental analysis of RS on all scales, the focus in the upcoming funding period will be on crystallographic texture. In addition to consid-ering the texture gradient across sheet thickness, the influence of deformation-driven texture evolution will be investigated numerically and experimentally. The methods for simulation and analysis of RS developed in the project will be validated on all scales and additionally applied within cross-project benchmarks.The research project is carried out as a joint project between the IFU, University of Stuttgart, the IAM-WK and the ITM-KM of the Karlsruhe Institute of Technology (KIT) within the frame-work of the call for proposals of the Priority Program 2013.