Date of Award
Masters of Civil Engineering Degree
Civil And Environmental Engineering
Dr. Srinivas Allena
Dr. Lutful I. Khan
Shape memory alloys (SMAs), such as Nitinol (i.e., NiTi), are of numerous importance in engineering applications due to their exceptional superelasticity and shape memory properties. Applications of a Shape Memory Alloy (SMA) in alleviating the seismic vibration response of civil infrastructure is attaining momentum. “Shape Memory” indicates that the material recollects its original formed shape. SMA has two simple properties, Super-Elasticity and Shape Memory Effect (SME). The “Super-Elastic” behavior revealed by SMA materials, allows a full recovery of strains up to 8% from big cyclic deformations, whereas developing a hysteretic loop. SME permits the material to recover the primary shape which is considered as re-centering mechanism. The mechanism of shape recovery comprises two crystallographic phases, Martensite and Austenite, and the transformations amongst them. The Austenite phase offers more stiffness than the Martensite phase. Phase transformation happens among Martensite and Austenite subject upon temperature and stress. These exceptional properties result in high damping and repeatable re-centering abilities which is an advantage in several civil infrastructure applications, exclusively in seismic vibration control devices. In recent years, additive manufacturing (AM) processes have been used to produce complex NiTi components, which provide the ability to tailor microstructure and thus the critical properties of the alloys. SMAs have also been explored progressively by the earthquake engineering community, because of their extraordinary self-centering (SC) and energy-dissipating competences. This work analytically presents numerical investigations iv executed to comprehend the numerical behavior of an SMA damper. Part of the numerical model is assessed against an experimental result by Zhai et al. (2020) and exhibited reasonable accuracy. The SMA damper with SC function under monotonic, fatigue cyclic and quasi-static cyclic loading is presented. The numerical results demonstrate that outstanding and stable flag-shaped hysteresis loops are exhibited in multiple loading cycles, indicating good energy dissipation, large deformation and ductility abilities. The stress-strain states with dissimilar phase transformation are also discussed in this work.
Boateng, Anthony Addai, "Effect of Geometry And Material on the Response of A Shape Memory Alloy (sma) Earthquake Damper" (2020). ETD Archive. 1253.