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Lecture

WEB Properties of additively manufactured metallic metamaterials using a superelastic NiTi shape memory alloy

Tuesday (22.09.2020)
16:25 - 16:40 F: Functional Materials, Surfaces, and Devices 2
Part of:


The pantographic structure has drawn interest as a mechanical metamaterial because it can be subjected to a large deformation while remaining in an elastic regime. Mechanical metamaterials like the pantograph show unusual mechanical behavior and often exhibit a complex shape. These shapes make it challenging to manufacture functional metallic metamaterials whereby laser powder bed fusion (LPBF) can offer a solution for the fabrication of bulk as well as filigree and complex shapes. Due to technical improvement in the additive manufacturing process of metal alloys, the fabrication of filigree structures around 150 µm is possible. This development offers an enormous potential in the design of metamaterials. The technical progress of the LPBF-process in combination with the unique mechanical behavior of shape memory alloys offers additional possibilities, viz. functional integration. In particular, it allows high global (structure) and local deformation (material) by using the pseudoelastic effect.

 

In our study, we demonstrate that metallic metamaterials, viz. pantographic structures of the size of 6 x 30 x 5 mm3, can be manufactured from a Ni50.9Ti49.1 (at.%) shape memory alloy by LPBF. First, conventional as well as adaptive scanning strategies were used to study the influence on the quality of filigree and bulk specimens. In a second step, the mechanical behavior of as-built, non-standardized tensile and torsion samples were tested and compared to further additively manufactured counterparts (Ti-based: Ti-6Al-4V, Fe-based: X3NiCoMoTi18-9-5). The results of the applied materials prove that NiTi specimens due to superelasticity in the as-built state are advantageous in terms of deformability. Consequently, the potential of the aforementioned shape memory alloy has been evaluated by tensile testing of pantographic NiTi structures.

 

Our work implies that superelastic NiTi shape memory materials are promising alloys for the fabrication of metallic structures from the micro- (single struts, lattices) to the macroscale (bulk specimens, pantographs). The obtained findings can be used in the near future as an experimental basis for the development of corresponding simulations as well as the design and processing of structural-dynamic, complex parts with bistable mechanisms.

Speaker:
Florian Gutmann
Fraunhofer Institute for High-Speed Dynamics, Ernst-Mach-Institut - EMI
Additional Authors:
  • Tobias Gustmann
    Fraunhofer IWU
  • Konstantin Kappe
    Fraunhofer EMI
  • Hannes Korn
    Fraunhofer IWU
  • Dr. Bernhard Müller
    Fraunhofer-Institut für Werkzeugmaschinen und Umformtechnik IWU