PSI - Issue 42

4

Author name / Structural Integrity Procedia 00 (2019) 000 – 000

Costanzo Bellini et al. / Procedia Structural Integrity 42 (2022) 1299–1305

1302

Fig. 3. Stress-Strain behavior of NiTi in the cycle 1.

Fig. 4. Diffraction spectra at different strain. Fig. 5 shows the effect of the hysteresis taking into account the diffraction of the =5% specimen achieved under loading and unloading conditions. It is worth noting that the difference of the stress level is not the only differences of the hysteresis, but as is shown in the diffraction spectra, the differences are also in terms of microstructure. Under loading conditions, the main phases present in the microstructure is the austenite (red peaks), while in unloading condition it is the martensite (green peaks). According to the model proposed by Di Cocco et al. 2018 and Berto et al. 2021, in order to calculate the mechanical behaviour of the NiTi, Young modulus can be expressed by the relation (1)

(1)