Nature-inspired optimization of tubular joints for metal 3D printing

Steel tubular frames are often used to build a variety of structures because of their optimal mechanical properties and attractive forms. However, their joint fabrication involves a vast quantity of cutting and welding works, which induces high labour costs, material waste, and environmental pollution. The construction industry dominates the global carbon footprint, and it needs more sustainable products. Nature's structures are also often tubular, and their joints (e.g. the knees of a human body, the nodes of trees and plants) are intrinsically optimized to maximize stiffness, resistance, and robustness. The 3D metal printing technology can enable a nature-inspired optimization of steel tubular joints, saving material waste and decreasing fabrication costs as well as the carbon footprint of the sector, since it is free from the constraints of traditional manufacturing. In this study, we designed new tubular joint shapes using solid isotropic material with the penalization (SIMP) method. The objective of the optimization was to maximize the structural performance of the node. The optimized node that used to be achieved after a complex manufacturing process composed of numerous cutting and welding operations, can now be 3D printed and then connected to the rest of the joint leading to a shorter fabrication time. We quantified the joints' structural performance with different grades of optimization using non-linear finite element analysis. Compared with the conventional joint shapes, the new geometries offered a higher stiffness, resistance, and robustness. We performed a powder bed fusion simulation to analyze the residual stresses after production, and estimated the cost of the new solutions.

Automated summary

In this study, new tubular joint shapes were designed using 3D metal printing technology to optimize structural performance, reduce manufacturing costs, and decrease the carbon footprint. The optimized nodes can now be 3D printed and connected to the rest of the joint, leading to a shorter fabrication time. Structural performance of the joints was quantified with non-linear finite element analysis, showing that the new geometries offered higher stiffness, resistance, and robustness compared to conventional joint shapes.