As access to Shape Memory Alloys (SMAs) has expanded beyond their use as linear wires, the need for characterizing more complex forms that account for the effects of multi-axial stress, strain, and displacement has become increasingly important in actuator design. The novel uses of SMA actuators have also moved the devices into previously unexplored loading conditions, where established theory does not adequately model the real behavior. This work seeks to alleviate some of these issues by addressing problems with the most common multi-axial stress devices: helical springs. New applications are requiring high forces in small spaces, where SMAs' high work density makes them ideal. It was found in this work that springs with small spring indices (the ratio of the spring diameter over the wire diameter) deviated greatly between data and theory. This result was caused by the residual plastic deformation induced in the material during the manufacturing process. A secondary analysis accounted for this deviation using an empirical loss factor based on the evolving internal strain of the system. This method allows for the accurate prediction of SMA spring deflection of low spring index. Additionally, to better characterize SMA actuators as a whole, the special case of a helical beam was carefully examined. A generalized static helical beam was derived using an analytical load equilibrium approach. This created a set of closed-form equations that solve the internal loadings exactly. Using these loadings, a prediction of the displacements and rotations can be found by expanding upon the Euler – Bernoulli Beam Theory. This generalized static helical beam theory provides a toolset that can predict springs of any section length (full or partial turns) undergoing any multiaxial loading. This work benefitted from the financial support of NASA SBIR Phase 1 (NNX17CM48P) and NASA SBIR Phase II (NNX17CJ07C) sub-awards to UCF.
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Master of Science in Mechanical Engineering (M.S.M.E.)
College of Engineering and Computer Science
Mechanical and Aerospace Engineering
Mechanical Engineering; Mechanical Systems
Length of Campus-only Access
Masters Thesis (Open Access)
Puchaty, Ryan, "Experimental, Analytical and Computational Analyses of Linear and Radial Shape Memory Alloy Helical Actuators" (2020). Electronic Theses and Dissertations, 2020-. 812.