Predictive Tools for the Improvement of Shape Memory Alloy Performance
Author | : Richard Paul Blocher |
Publisher | : |
Total Pages | : 77 |
Release | : 2019 |
Genre | : Materials |
ISBN | : |
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The superelastic and actuation performance of shape memory alloys depends greatly upon the composition and processing of the alloy, as well as the operating temperature range and stresses involved in its implementation. This thesis is in two parts. The first presents a design parameter to help classify shape memory alloys and quantify their performance as torque tube actuators. It studies the effects of crystallographic texture variation, actuator biasing stress, alloy composition, and alloy system on shape memory torque tube performance through a combination of simulation and aggregation of experimental data. Finally, a torque tube design for use in aircraft gas turbine engines is recommended based on these findings. The second part of the thesis seeks to mechanistically explain why the alloy composition effects on performance in NiTiHf shape memory alloys occur. It is hypothesized that the stabilization of martensite occurs because of the lattice mismatch strain between the “H-phase” precipitate phase, which form with the heat treatment of these alloys, and the cubic austenite phase. From this hypothesis, a model for predictions of martensite microstructures is created, and the reduction in strain energy of the formation of these microstructures is estimated.