Design and manufacturing concepts for additively manufactured lightweight structures
Additive manufacturing, especially LPBF, has enormous growth potential. At present, a number of unanswered questions in the areas of design, process control and operational stability stand in the way of a widespread transfer of LPBF technology.
Questions concerning design relate to the lack of adapted design rules and principles. Compared to conventional manufacturing processes, most designers lack experience in the design of lightweight components, which results in an uneconomical use of the technology and a low utilization of the lightweight potential. Through locally adapted process control, the LPBF process offers the potential to produce lattice structures at the meso level. These have great potential for low-material and economical production. Their reliable production by LPBF and the resulting mechanical properties are highly dependent on the process control. This adapted process control has already been developed in initial research work, but must be further developed to series maturity and transferred to a broad industrial application with methodological support. Similarly, there is a lack of a database with regard to fatigue strength, which gives rise to considerable uncertainties in the reliability assessment of additively manufactured lightweight components with regard to fatigue loading and form conformity.
The aim of the project is to demonstrate the industrial applicability of topologically optimized design and structurally integrative use of lattice structures in quasi-static, dynamically and cyclically loaded components using L-PBF technology. The basis for this is the reproducible, automated generation of lattice structures and a determination of validated material parameters for specific lightweight structures. The central solution approach in both areas is the combination of physically-based models (white-box) with data-based machine learning methods (black-box) in near real-time capable grey-box models for the implementation of innovative targeted manufacturing and dimensioning concepts. It is crucial to be able to predict local material and component behavior, generated by peculiarities of the additive manufacturing process, and to take them into account in the design or construction and calculation. The focus with regard to the load shape should be on the cyclic material behavior. Depending on the component's area of application, however, the static design strength and the plastic deformation and failure behavior in misuse and crash load cases must also be considered. Only a comprehensive evaluation of the loads on a component using CAE methods will allow effective and targeted optimization. To develop and test the method, investigations are carried out on lightweight structures made of various aluminum alloys. As a result, design and manufacturing concepts will contribute to the reduction of market entry barriers and will be further communicated both through influence in standardization and in workshops for practical application.
Starting with the selection of components or assemblies through methodical evaluation of the lightweight potential, lightweight structure designs are developed for the corresponding components. The project is divided into the two parallel tracks of lattice structures and topology-optimized designs. For each of these two concepts, process strategies will be developed to produce homogeneous component properties (surface, microstructure) for evaluable cyclic strength. Process monitoring systems will also provide characteristic parameters to correlate the process with the resulting properties. Cyclic strength properties are evaluated by considering damage behavior and material models, and combining these in innovative grey-box models. Finally, design and dimensioning guidelines are derived from this evaluation in combination with the design.