The overarching motivations for the majority of development projects at IFU, both in industry and research, continue to be resource conservation and lightweight construction. In light of the increasing prevalence of lightweight requirements, sheet metal components must exhibit higher stiffness while maintaining the lowest possible weight. Additionally, designers demand not only lighter sheet metal components but also components with higher precision and geometric complexity. Consequently, research at IFU in this field focuses on process and tool development, as well as improving the value creation of sheet metal parts and body components. Two strategies are pursued in essence:
- "Lightweight and stiff": Sheet metal components made from lightweight materials with high stiffness.
- "Thin-walled and high-strength": Components made from thin and high-strength sheet metal materials.
The challenge in using modern metallic lightweight materials is to deliver outstanding quality despite their sometimes limited processability compared to conventional bodywork materials, while also keeping manufacturing costs of the component within limits. One solution is to develop high-strength and ductile aluminum and magnesium alloys, along with innovative heat treatment processes, which can reduce component wall thicknesses. The Institute of Forming Technology (IFU) at the University of Stuttgart has made a significant contribution to the overall objectives of the collaborative project SMiLE. This has included the following activities: the characterization of the forming behavior of novel, modified aluminum and magnesium alloys for In collaboration with material manufacturers, the Institute of Forming Technology (IFU) at the University of Stuttgart has undertaken the characterization of the forming behavior of sheets and profiles. This has involved the improvement of failure behavior description in the production of body components, thereby enhancing the utilization of forming potential. Furthermore, the IFU has accompanied component manufacturing, participated in the characterization of component properties, and demonstrated the lightweight potential of the new developments.Ultimately, the objective of this project is to expand the material navigator, which was developed at IFU (see figure), with additional criteria and innovative materials for sheet and profile forming.
The topic of lightweight construction is of great importance in numerous industries, including electromobility, mechanical engineering, and heavy construction. Honeycomb structures made from paper or sheet metal offer a significant potential for reducing weight and contributing to the production of sustainable products. This research project is a collaborative effort between the Institute of Forming Technology (IFU) and the Institute of Aircraft Design (IFB). The goal is to combine expertise in forming technology with the characterization and design of fold structures.
In the initial phase of the project, the impact of distinct pre-structuring geometries and their implementation through forming techniques, such as embossing or roll kneading, is examined. DC04, DP500, and AW 5182 are utilized as experimental materials. The experimental investigations are supplemented by numerical simulations. The developed numerical model offers a more profound comprehension of the flow and strain hardening behavior at the bending edge of the individual cells.
The investigations yielded an optimal pre-structuring geometry and roll kneading as the most effective method for introduction. Based on this optimal fold cell geometry, a new folding tool concept was developed and subsequently built in the next phase of the project. Notably, the pre-structured plate plays an active role in the tool. The tool consists of numerous prisms guided in the x and y directions. The function of the prisms is to transmit the force applied by the press ram into the plate and initiate unfolding. However, the kinematics of unfolding are determined by the chosen pre-structuring geometry. By using this innovative folding tool, a complete and flawless unfolding can be achieved in a single stroke for the first time.
The objective of the BMWi consortium project CO2-HyChain is to further develop solutions previously researched at laboratory scale for the production of high-strength aluminum and hybrid aluminum-steel Tailor Welded Blanks (TWB) through technology transfer from research institutions to industrial manufacturers/users. Additionally, the aim is to enhance the entire value chain maturity level from 3 to 7.
In the context of the institute's project, both inverse and reverse numerical design methodologies for manufacturing hybrid sheet metal components are being developed. Concurrently, a comprehensive characterization of the respective material combinations and the microstructure of the welding zones has been conducted. The characterization focused on the weld seam to determine the forming and failure behavior of the Tailor Welded Blanks. The investigations revealed that the weld seam exhibited significantly different behaviors depending on the direction of loading relative to the orientation of the weld seam. The studies indicated that the formability was higher when oriented at 0° to the weld seam direction compared to 90° (see image).
In summary, the results of the characterization experiments can be represented in the limit strain diagram.
With the insights gained, the project will proceed to develop the inverse and reverse numerical design methodologies and adapt the tooling technology, with the objective of enabling the production of demonstrator components (see image) in subsequent stages of the project.
Modern automotive crash structures typically comprise sheet metal components and are subjected to loads in crash scenarios that necessitate both high strength and sufficient energy absorption capabilities. The design of these components is influenced by a number of factors, including the available installation space, manufacturing processes suitable for producing such crash structures, and the intended material for the component.
Currently, the design of such crash-relevant components for optimal load-bearing capacity often involves complex geometric topology optimizations or targeted local property modifications through heat treatments or special material combinations (e.g., Tailored Blanks). These approaches are necessary to ensure that the components can meet the stringent safety and performance requirements during a crash event.
In conclusion, the sizing and design of contemporary crash structures are driven by the necessity to achieve a balance between strength, energy absorption, available manufacturing methods, and the material properties specific to each application, ensuring effective performance under crash conditions.
The project, entitled "Manufacturing Crash-Optimized Sheet Metal Components through Embossing," is based on promising findings and preliminary investigations into the modification of properties of blanks or sheet metal components through near-surface embossing. This potential for property modification is intended to be leveraged for the structural optimization of sheet metal components relevant to crash scenarios through the planned research project. The project hypothesizes that crash scenarios can be specifically influenced by partial surface structuring of high-strength steel sheets through an embossing process. The relevant crash properties include deformation behavior, energy absorption capacity, as well as stiffness and strength, which depend on the component and loading scenario.
The targeted adjustment of properties corresponding to the given loading scenario is based on the cold work hardening introduced into the sheet metal, which varies in intensity depending on the chosen embossing pattern and depth of impressions. The primary objective of the proposed research project is to develop a simulation-based optimization methodology based on the investigation results, capable of predicting the influence of near-surface embossments on the properties of structural components. This methodology will facilitate topology optimizations within certain limits at later stages of the vehicle structure design process for crash scenarios. In conclusion, the simulation-based optimization methodology, which employs the mapping from volume to shell elements (see Fig. 1), will facilitate enhanced design of embossed crash components, taking into account component geometry, material, and specific loading conditions. This approach is anticipated to yield economic and process improvements in comparison to previous methods aimed at enhancing crash and lightweight performance.