Optimization of strut diameters in lattice structures: Fid-Bau Portal

Optimization of strut diameters in lattice structures

Teufelhart, S. / Reinhart, G.

It has been exemplified that Additive Layer Manufacturing has a great potential for the production of lightweight components. Especially mesoscopic approaches like lattice structures exhibit great properties for mass reduction. However, these structures are currently designed as periodic patterns. This leads to unfavorable bending loads in the single struts and uneven stresses over the structure. To improve the structures build-up, an optimization approach has been introduced, which adapts the course of the structure to the flux of force in a part. The great potential of this proceeding has been shown at the example of a shear loaded beam. Here, it was possible to enhance the ratio of the maximum applicable force to the structures mass for 124% compared to a periodic structure. Another optimization goal of the presented approach is the adaption of the struts diameters with respect to the appearing stresses. First, an optimization has been introduced, at which the struts diameters are optimized uniformly until a predetermined maximum stress is reached. Thus, it was possible to almost exactly reach the desired stress of 32 N/mm². However, the loads in the single struts were still varying. Therefore, another second optimization approach has been applied. Here, the single struts were adapted to their respective stresses individually. However, several different procedures concerning the fixed and loose rotational degrees of freedom and the optimization goal (maximum of average von-Mises stress) had to be investigated to come to an optimization procedure, which does not lead to unwanted bending loads in the beams and which can be performed without any manual interaction. Thus, the ratio of the maximum applicable force to the structures mass could be enhanced for 80%. However, FEM calculations with a tree dimensional model of the structure have shown that there are severe notch stresses appearing at the nodes where the beams are merging. Therefore, a suitable node design will be developed in future works, which realizes a smooth connection of the struts and therefore reduces stress peaks. Beyond that, another procedure for the optimization of the struts diameters will be developed, which makes it possible to reach a predefined stiffness of the structure with the application of a minimum mass. Furthermore, a rule based algorithm will be developed, which is able to automatically build up a structure that is adapted to the flux of force of a part. Currently, this step has to be done with great manual effort.