ALLEGRO – High-performance aluminum alloy components.

Process-related structural durability, ­fatigue life concept, cyclic material behavior

ALLEGRO – High-performance aluminum alloy components through resource-optimized process technologies.

Recent developments in the field of electromobility and the corresponding demand for ever-increasing ranges of electric vehicles require new production technologies that contribute to maximizing the utilization potential of lightweight materials. Additional potential of lightweight materials must be explored, especially with regard to developments in electromobility. The key to this lies in combining ultra-high-strength aluminum alloys with new shaping processes to adapt local component characteristics as needed. Fatigue strength plays a central role in this case, as the process-induced properties are specifically used to improve the component fatigue life. For ”ALLEGRO”, Fraunhofer LBF scientists are evaluating the entire process chain as well as the increases in strength and fatigue life potential based on a bicycle frame.

The objective is to develop future technologies for ultra-high-strength aluminum alloys as part of the LOEWE focus on ”ALLEGRO” in order to achieve ecologically as well as economically efficient shaping processes with integrated heat treatment. These processes are then supposed to be used to manufacture semi-finished products with locally adapted properties that are aligned with the function and load according to the customer's area of application.

Along the process chain, the individual process steps influence the microstructure as well as the material properties and ultimately the component behavior. Utilization of the lightweight potential can be increased in a targeted manner by identifying local material properties that are induced through the manufacturing process and integrating them into the operational design and evaluation of cyclically stressed components and structures (process-based fatigue strength).

Numerical illustration of the test specimen using of a friction-stir-welded lap joint as an example.

New high-resolution test system to determine the local process-based influencing parameters on the cyclic material behavior.

Since components are usually made up of several semi-finished products, the availability of the graded semi-finished products must also be examined. The challenge with joining is to retain the grading of the semi-finished product or even introduce it though the joining process. Suitable joining methods for this purpose are laser beam welding, friction stir welding and magnetic pulse welding, all of which are examined in-depth in the project.

Existing assessment concepts of fatigue strength are currently limited in their ability to account for local material properties that were induced through the manufacturing process and thus the manufacturing background of the material.

Based on the characterization of the transient cyclic material behavior, existing evaluation concepts of fatigue strength are further developed at Fraunhofer LBF, while taking the manufacturing and joining processes into consideration. These improved fatigue life oriented design concepts provide the foundation for lightweight construction and sustainable product design.

Sponsors and partners

LOEWE LandesOffensive zur Entwicklung Wissenschaftlich-ökonomischer Exzellenz, Hessen

Universität Kassel, Technische Universität Darmstadt