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NiMn Based Ferromagnetic Shape Memory Alloys for Structural Health Monitoring
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With the push for advanced space craft and super structures requiring complex and inventive design and construction, monitoring of these structures will become ever increasingly more important. As the health and safety of the public will rely on the continued performance of these structures, monitoring them for damage and structural failure, or “health”, becomes paramount. First among these is acoustic monitoring through the use of piezoelectric sensors interacting with the acoustic vibrations that generally are present during damage processes. Their lightweight and simple construction, along with its ease of miniaturization has permitted their use in a number of civil and aerospace applications for structural health monitoring. Unfortunately, this monitoring method relies on active damage mechanisms to produce measurable acoustic events, can easily be overwhelmed from external vibrations or “noise,” and requires the sensors to be robustly designed and remain attached to surfaces for extended periods of time. Despite these drawbacks, it is one of the cheapest and most easily integrated methods for structural health monitoring. Therefore, a need exists to develop an additional system capable of monitoring the structure in the event of acoustic sensor failure, and can quickly confirm and quantify damage detected by the acoustic sensor network. This work proposes to embed magnetic shape memory particles to interact with stress concentrations at crack tips and operate in conjunction with the acoustic sensors. Magnetic shape memory alloys possess a unique relationship between stress and magnetization as the material undergoes a martensitic transformation from one crystallographic system to another. Herein, the feasibility of the idea is demonstrated through the consolidation of powder precursors of Niv43Cov7Mnv39Snv11 magnetic shape memory alloy and pure aluminum. The composite materials demonstrate similar thermo-magnetic properties to the starting Niv43Cov7Mnv39Snv11, and under certain processing conditions lead to a brittle, dual region diffusion zone that negatively affects mechanical properties of the composite. Composite manufactured with Niv43Cov7Mnv39Snv11 and aluminum 7075 yield better compatibility between the matrix and sensory particles, and demonstrated a change in magnetization at 300K from 65.8emu.g-1 at 0% compressive strain to 17.5 emu.g-1 at 11.8% compressive strain, successfully demonstrating the feasibility of the proposed method.
Subjectshape memory alloy
spark plasma sintering
Barta, Nicholas E. (2018). NiMn Based Ferromagnetic Shape Memory Alloys for Structural Health Monitoring. Doctoral dissertation, Texas A & M University. Available electronically from