Applying the Infrared Self-heating Method to a Comprehensive Fatigue Analysis of NiTi Shape Memory Alloys

This paper aims to seek expedited fatigue analysis methods using the infrared self-heating technique. The fatigue analysis of NiTi shape memory alloys is obtained through a hybrid approach: fatigue tests to failure yield relatively shorter fatigue lives, while determining the fatigue limit, normally involving extremely high cycles approaching 10⁷ cycles, is directly achieved via self-heating tests. This methodology significantly reduces testing cycles, costing only a fraction of the several-thousand-cycle tests typically required. The validity of this approach is successfully demonstrated through fatigue testing of 18Ni steel: the entire S–N curve is examined using the traditional fatigue test until a life of up to 10⁷ cycles, and the indicated fatigue limit agrees well with the one directly determined through the self-heating method. Subsequently, this developed approach is applied to the fatigue analysis of shape memory alloys under complex loading, enabling the concurrent estimation of the limits of phase transformation-dominated low-cycle fatigue and high-cycle fatigue in the elastic regime on a single specimen. The results obtained align well with other supporting evidence.