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，以定向产生薄壁金属零件的残余应力(RS)。成形诱导应力应变是为了提高主要承受动态载荷的板材结构构件的疲劳强度。在项目范围内，在第一和第二供资期间证明，通过结合成型和压花工艺，可以在薄壁金属零件中产生残余压缩应力，从而可持续地提高零件的循环使用强度。本研究的重点将放在粗大复相材料(双相钢X2CrNiN-23-4)的成形上。特别是，将系统地评估特定相微RS的贡献。在此背景下，一方面，在材料分析领域开发了用于本地遥感分析的测量和评估策略。另一方面，通过数值有效的平均场方法对I、II和III类RS进行基于机理的建模，为两相微结构中RS的双尺度建模提供了可能。这些实验和数值研究的结果最终导致了薄壁结构件的组合制造工艺的发展，通过将成形操作与同时压花和随后的重整相结合，以有针对性的方式引入压缩RS。第三个供资阶段的目的是将在前两个供资阶段中获得的关于RS的产生、分析、稳定性和模拟的知识转移到循环加载的实际部件上，特别是抽象的载板上。这包括刀具概念的整体数值设计及其制造实施。考虑到在供资阶段I和II中制定的测量、评价和模拟战略，以尽可能最准确地确定所有尺度(I至III.种类)中的载体板中诱导RS。对于RS在所有尺度上的模拟和实验分析，在即将到来的资助期，重点将放在晶体结构上。除了考虑板材厚度方向的织构梯度外，还将对变形驱动织构演化的影响进行数值和实验研究。项目中开发的遥感模拟和分析方法将在所有尺度上进行验证，并在跨项目基准中额外应用。该研究项目是IFU、斯图加特大学、IAM-WK和卡尔斯鲁厄理工学院(KIT)的ITM-KM在2013年优先计划征求建议书框架内进行的联合项目。

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.