Influence of Laser-Induced Surface Modifications on the Fatigue Behavior of SMA Wire Actuators

Abstract Ultrashort pulse lasers are common tools for surface structuring and marking of components. However, even finest structures generated by ultrashort laser processes may affect the mechanical properties of components. In the present work, the effects of laser-induced surface modifications on the fatigue behavior of pickled nickel titanium shape memory wires are investigated. Ultrafast Bessel beams have been utilized to create small microstructure-covered grooves on a defined area on the wire’s shell surface. Subsequently, the wires underwent fatigue testing until failure. The impact of laser processing on fatigue behavior and the resulting fracture surfaces were examined using scanning electron microscopy. It was found that laser defects generated with low fluences have a negligible impact on fatigue lives, as microcracks, which may cause failure, typically initiate at other more severe types of surface defects. However, we identified certain laser scanning strategies and other conditions like increased fluences, which can affect wire surface regions to become prone to fatigue crack initiation, resulting in reduced service lives.