Design and optimization of a new NiTi-based shape memory alloy structures for damping applications via additive manufacturing

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Abstract Shape Memory Alloys (SMA), such as NiTi-based systems, are functional materials suitable for damping applications due to their pseudoelastic effect. This property allows to obtain simple, lightweight structures capable of absorbing energy through a mechanical hysteresis and able to recover significant deformations. For this reason, SMA are attractive candidates for the development of novel devices in many fields, such as the biomedical one or in aerospace and in automotive. Recently, the development of Additive Manufacturing (AM) of metals has considerably expanded the design and production possibilities of SMA-based devices, potentially overcoming the limited workability of these materials through conventional manufacturing techniques, which is one of the main limitations to their wider adoption. This study presents a preliminary investigation of a NiTi octahedral cell structure fabricated via Laser Powder Bed Fusion (L-PBF) starting from a NiTi powder with Ni content of 50.8 at. %. Cells of different sizes were manufactured and subjected to compression tests up to 0.8 mm displacement in order to evaluate their mechanical and functional performances. Furthermore, a numeric model was used to redesign the geometry in order to optimize the structure's damping capacity. The material input data of the numerical model were obtained from mechanical and thermal analyses on square prisms, which were printed with the primary axis oriented perpendicular and at an inclination of 60° to the building platform. Finally, the optimized cell was manufactured and mechanically tested at different temperatures. The obtained results prove the high efficiency of the structure when used for damping applications and highlight the potential of AM to produce NiTi structures that combine load-bearing capabilities and functional responses.