Fatigue and Functional Degradation in Shape-Memory Structural Alloys (SMAs)
Year: 2026
Type: dissertation
Abstract: The incorporation of Shape Memory Alloys (SMAs), such as Nitinol (Nickel-Titanium), into structural engineering applications represents an advanced technological breakthrough for seismic resilience, self-centering brace systems, and vibration-control dampers. SMAs possess a unique superelastic capability, allowing them to undergo large inelastic strains and automatically recover their original geometry upon the removal of applied loads, thereby eliminating permanent structural drift after severe seismic events. However, the core engineering dilemma involves the long-term mechanical fatigue and functional degradation of these intelligent alloys under repetitive loading cycles. As SMAs undergo successive phase transformation cycles (austenite-martensite conversions) during intense dynamic excitations, the material accumulates microscopic internal crystalline slip and dislocation networks. This cyclical microstructural degradation leads to functional fatigue—characterized by a progressive reduction in the alloy's re-centering force, increased residual plastic deformation, and shifts in stress-strain hysteretic damping efficiency over time. Standard structural design codes lack constitutive models to predict how these functional properties degrade after thousands of minor-to-moderate cyclic events, making it difficult to guarantee that an SMA-based seismic retrofit system will perform reliably decades after its initial installation without performance drift.
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7214778624