Structural health monitoring using embedded magnetic shape memory alloys for magnetic sensing

Abstract

In the field of structural health monitoring (SHM), innovative methods of non-destructive evaluation (NDE) are currently being investigated with the purpose of safer, longer lasting structures. While current SHM is dominated by acoustic emission and vibration-based methods, it is desirable to integrate NDE techniques with existing structural reinforcement techniques which increase structural service life. Multifunctional materials that can detect internal structural damage while also increasing structural service life offer an inherent advantage as construction materials to be integrated into new and existing structures. Embedding shape memory alloy (SMA) wires in concrete components offers the potential to monitor their structural health via external magnetic field sensing. SMAs have been used to close internal cracks, reinforce concrete structures, and reduce fatigue under cyclic loading, so the addition of such a multi-functional material for the purpose of structural evaluation is very desirable. Thus an evaluation of SMAs for magnetic sensing is required for both the structural and magnetic domains. A concrete beam containing iron-based magnetic SMA (MSMA) wire is subjected to a three point bend test where structural damage is induced, resulting in a localized phase change of the MSMA wire. Magnetic field lines passing through the embedded MSMA domain are altered by this phase change and can thus be used to detect damage within the structure. A good correlation is observed between the computational and experimental results, and the magnetic sensing sensitivity is explored via a robust computational model to evaluate the effectiveness of external magnetic sensing.