Understanding fatigue damage mechanisms of L-PBF manufactured lattice structures through experimental and numerical methods

• Applicants: Professor Dr.-Ing. Sebastian Münstermann; Professor Dr.-Ing. Frank Walther
• Subject Area: Materials in Sintering Processes and Generative Manufacturing Processes ; Mechanical Properties of Metallic Materials and their Microstructural Origins
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 544796565

One of the major challenges in using additive manufacturing (AM) materials and lightweight structures is the need for a better understanding and further development of evaluation and design approaches that can ensure damage tolerance. The project aims to address this challenge by characterizing the fatigue damage behavior of 316L alloy lightweight lattice structures produced by selective laser melting/laser powder-bed-fusion (L-PBF), which has yet to be studied in the literature. To fulfill the requirements of fatigue resistance and damage tolerance, there is a need for more knowledge on efficient application options of AM non-trivial steel structures. The overarching goal is to establish a new strategy for investigating fatigue properties and designing the microstructure of AM steels using mechanism-informed multiscale modeling approaches. The project will develop materials design concepts required to design L-PBF 316L stainless steel lattice structures and demonstrate their applicability. A reliable and efficient strategy for investigating fatigue mechanisms of AM steels under complex loading conditions is aimed at by quantitatively identifying the individual impacts of microstructural features, defects, and roughness on the fatigue properties under multiaxial loading conditions. This proposal will achieve this by combining in-situ testing and multiscale modeling approaches to reveal the dominant factors controlling fatigue damage progress in AM steel structures. To understand the damage mechanisms and identify the most critical factor controlling the fatigue properties of L-PBF 316L lattice structures, the focus is on the competitive relationship between microstructure features, internal defects, surface roughness, and stress conditions. To comprehensively characterize the microstructure and defects features in L-PBF 316L, particular attention is given to use virtual testing methods to enhance the digitalization and reconstruction of microstructure models for AM steels. Systematic investigations will be conducted by quantitatively characterizing microstructure features, defects, and surface conditions using a combination of in-situ computed tomography, digital volume correlation, and fractography analysis. Insights into identifying the prevailing damage-controlling parameters will be provided using parametric virtual laboratory crystal plasticity simulations, using synthetic microstructure models with systematically altered microstructure, defect, and roughness profiles. 316L lattice structures can reduce the amount of material needed to create a product, reducing waste and lowering environmental impacts. They can increase the strength-to-weight ratio of a product, making it more efficient and reducing energy usage.

• DFG Programme: Research Grants