Constitutive modeling of shape memory alloys /
A constitutive model for polycrystalline SMAs is formulated using a general thermodynamic framework of internal stat evariable theory. A generic form of Gibbs free energy potential is derived by performing a micromechanical analysis over a constitutive Representative Volume Element (RVE). The sele...
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| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1996.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=739640061&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | A constitutive model for polycrystalline SMAs is formulated using a general thermodynamic framework of internal stat evariable theory. A generic form of Gibbs free energy potential is derived by performing a micromechanical analysis over a constitutive Representative Volume Element (RVE). The selection of internal state variables describing the average geometry and the elastic interactions among transformed martensite, surrounding parent phase, and existing plastic strains is discussed. To propose evolution equations for the internal state variables, transformation hardening mechanisms due to various material heterogeneities are studied. Due to above efforts, both stress induced and thermally induced phase transformations of trained SMAs with two way shape memory effect can be modeled in the present unified formulation. To investigate the evolution of plastic strains and the creation of two way memory effect with respect to loading cycles, experiments of cyclic thermally induced phase transformation at various levels of the applied load is performed up to two thousand cycles. Evolution equations for plastic strains and plastically related back and drag stresses with respect to the cyclic loading are proposed based on the experimental observations and the theoretical analysis performed in the first part of the dissertation. To the knowledge of the author, the present work provides, for the first time, a working model capable of describing cyclic thermomechanical response of SMAs for both stress induced and thermally induced phase transformations with evolving plastic strains and two way memory effect with respect to loading cycles. The results show that the theoretical predictions are in good agreement with experimental measurements. |
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| Item Description: | Vita. "Major Subject: Aerospace Engineering". |
| Physical Description: | xv, 195 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 180-192. |