Fatigue analysis of shape memory alloys by self-heating method

In recent years, self-heating method, which is based on temperature measurements, has been proposed as a faster and cheaper alternative to classical fatigue tests. In the present study, one-dimensional thermomechanical constitutive equations of shape memory alloys (SMAs) were implemented into the self-heating method by using a probabilistic two-scale model in order to study fatigue of these alloys. This model was shown to be capable of predicting the S/N curve of these alloys as well as its scatter by using probability relations. To identify parameters of the two-scale model, self-heating experiments were conducted. The presented approach was developed to predict the S/N curve of both raw specimens and heterogeneous ones with surface treatments for any failure probability in a much shorter time compared to the classical methods. The heterogeneous samples were made by hydrogenating the surface of virgin specimens. To investigate validity of the numerical results, the theoretical predictions were compared with experimental data and a good agreement was observed.