Thermomechanical modeling of NiTi shape memory alloys including plasticity

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2022-8

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Küçüker, Hamdi Alpay

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Shape memory alloys (SMA) are unique materials with an ability to recover their original shape from large deformations when unloaded and/or subjected to heat. Their ability to recover from large strains, due to martensitic transformation, even under excessive loading allows them to be used in various different sectors including aerospace, biomedical and automotive. The present thesis summarizes the studies on constitutive modelling of SMAs and the effect of plasticity on it. Based on the experiments and tests presented in the literature, an already existing 3D constitutive model is modified in order to include the effect of plastic strain. The model used in this thesis, includes the conventional characteristic behaviour of SMA, namely two way shape memory effect (TWSME) and superelasticity, as well as the plastic strain. The generated constitutive model is implemented into finite element tool via a user subroutine code. The model can capture the strains caused from both transformation and plastic deformation. The model is applied to the analysis of a spring in tension, simple tension test and a three point bending test. The proposed plasticity modified constitutive model predicted the behaviour of the SMA and showed similar results with the experimental data available in the literature.

Subject Keywords

Shape Memory Alloys, Plasticity, Martensitic Transformation, Constitutive Equation, Modelling

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https://hdl.handle.net/11511/99497

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

H. A. Küçüker, “Thermomechanical modeling of NiTi shape memory alloys including plasticity,” M.S. - Master of Science, Middle East Technical University, 2022.