Finite strain modeling of coupled thermo-mechanical behavior of polycrystalline Ni-Ti shape memory alloys

Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Makina Mühendisliği Bölümü, Türkiye

Tezin Onay Tarihi: 2017

Öğrenci: VAHID REZAZADEH FASAGHANDIS

Danışman: HÜSNÜ DAL

Özet:

Shape memory alloys (SMAs) hold a signiﬁcant importance in diﬀerent areas such as aeronautics,adaptive structures,oil/gas down-hole, and high-temperature applications of automobile industry. Nowadays,researchers have already become well-aware of these applications and attempted to discover all the primary features of this speciﬁc smart material. Meanwhile, there is a growing eﬀort to produce mathematical models in order to imitate the related behavior in a precise manner. Due to the crucial need to have a ﬁne computational model, we established a constitutive theory based on the ﬁnite strain framework of continuum mechanics. The presented thermo-mechanically coupled model can perfectly reproduce all behavior of Ni-Ti SMAs including martensitic phase transformation, pseudoelasticity, and one-way shape memory eﬀect. Our constitutive model is also able to investigate the strain-rate and temperature dependency of the loading conditions. This work aims at utilising ﬁnite strain plasticity set- ting with purely thermodynamically consistent constitutive equations. In this framework, a user material subroutine (UMAT) is written and implemented into ABAQUS/Implicit (2016) ﬁnite element program. Veriﬁcation of the model is carried out by the calibrated experimental ﬁndings which exist in the literature. Numerical simulations of developed constitutive model successfully denote the ability of our phenomenological model in capturing diﬀerent memory eﬀects of Ni-Ti SMAs under stress-strain-temperature cycling.