In this master’s thesis, the energy-related and elastomechanical response of a specimen made of the superelastic alloy Nitinol is investigated. The specimen was subjected to tensile, compressive, and torsional loading using a multiaxial static and dynamic testing system, while the response was recorded using a Digital Image Correlation (DIC) system. The acquired data was exported to Microsoft Excel (MS Excel) and further processed using the Wolfram Mathematica (WM) software environment. The data processing procedure included the identification of loading cycles, representation in a coordinate system, transformation of the coordinate system from the global Cartesian system of the data acquisition device to the local cylindrical coordinate system of the specimen, and the calculation of work and the stress–strain response of the specimen. Based on the stress–strain response in the transverse directions, the most suitable data for evaluation in the principal direction were identified. By comparing the input and recovered mechanical work, we found that torsional loading exhibited the highest degree of energy reversibility, while tensile loading exhibited the lowest. The energy dissipation under compressive loading was slightly lower but comparable to that under tensile loading. During tensile loading, a correlation between the stress–strain responses σ$_{zz}$(ε$_{zz}$) and σ$_{zz}$(ε$_{φφ}$) was observed, while during compressive loading, buckling was identified. Furthermore, the parallelogram rheological model was assigned to all stress–strain responses. In comparison with literature, the values obtained of the elastic moduli were generally lower. In this context, we highlighted the specific characteristics of the data-processing methodology based on the DIC system.
|
