Temperature-Controlled Laser Processing of Shape Memory Wires: Spherical Ends as Connectors for System Integration

Abstract

Nickel–Titanium-based shape memory alloys have reached a high technological relevance in the medical field and also for actuation/energy conversion. At present, the interest in new actuation solutions is steadily increasing. However, one important challenge for the design of new actuators is the lack of connection and coupling options, which often hinders a reliable system integration. To address this challenge, this study presents a temperature-controlled laser processing approach for the generation of spherical ends on shape memory wires, which allow a relatively simple integration into different types of systems (e.g., printed circuit boards) in a form-fitting manner. For this purpose, an experimental setup with an integrated pyrometer was used to establish spherical ends on thin NiTi wires with a diameter of 0.24 mm. The resulting microstructures and the functional properties were investigated using scanning electron microscopy, thermal analysis, uniaxial tensile testing, actuation fatigue testing, and hardness measurements. The results obtained in the present study indicate that our laser procedure successfully yields reliable connection options for NiTi wires, without harming the functional performance of the material.