Mr. Allen Davis Profile

Allen Davis

Graduate Researcher at Texas A&M Univ

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Proceedings Article | 1 April 2019 Presentation + Paper

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

Allen Davis, Mirmilad Mirsayar, Darren Hartl

Proceedings Volume 10971, 109710O (2019) https://doi.org/10.1117/12.2514131

KEYWORDS: Magnetism, Magnetic sensors, Shape memory alloys, Structural health monitoring, Nondestructive evaluation, Finite element methods

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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.

Proceedings Article | 1 April 2019 Presentation + Paper

Control of thermal deflection in concrete structures using iron-based shape memory alloys

B. Edmiston, A. Davis, M. Mirsayar, D. Hartl

Proceedings Volume 10971, 109710P (2019) https://doi.org/10.1117/12.2514140

KEYWORDS: Shape memory alloys, Structural design, Finite element methods

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Mitigating the structural damage caused by thermal expansion cycles is a primary objective in the design of concrete structures, such as bridges or buildings. One method to achieve this goal is the introduction of shape memory alloys (SMAs) as a replacement of traditional steel reinforcements in concrete structures. SMAs exhibit a characteristic known as “shape memory effect,” which allows the recovery of large deformations through the alloy’s martensite and austenite phase transformations. This effect gives SMAs an inherent advantage over steel. The purpose of this paper is to characterize the effect of an embedded SMA rod on a concrete system undergoing a thermal cycle, and to optimize the configuration of these materials. To achieve these ends, a system is modeled in Abaqus, a software suite for finite element analysis, consisting of a concrete block with an embedded, prestrained SMA rod, in which the concrete and SMA material properties have been determined from experimentation and secondary research. A set of the SMA’s properties (max transformation strain, coefficient of thermal expansion, stress influence coefficients, and volume fraction of SMA to concrete) are iteratively altered to produce characterization of the rod’s effect on the system, and then the same set are again altered using a multi-objective optimization tool to minimize deflection and maximize the temperature where concrete damage occurs. This approach is a cost-effective method to characterize the effects of these material properties and produce results that can be utilized in future projects where SMAs are deployed in large-scale concrete structures.

Proceedings Article | 27 March 2018 Paper

Structural health monitoring for DOT using magnetic shape memory alloy cables in concrete

Allen Davis, Mirmilad Mirsayar, Emery Sheahan, Darren Hartl

Proceedings Volume 10599, 105990A (2018) https://doi.org/10.1117/12.2300910

KEYWORDS: Magnetism, Magnetic sensors, Shape memory alloys, Structural health monitoring, Sensors, Nondestructive evaluation, Mechanics, Statistical modeling, Solids, Corrosion

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Embedding shape memory alloy (SMA) wires in concrete components offers the potential to monitor their structural health via external magnetic field sensing. Currently, structural health monitoring (SHM) is dominated by acoustic emission and vibration-based methods. Thus, it is attractive to pursue alternative damage sensing techniques that may lower the cost or increase the accuracy of SHM. In this work, SHM via magnetic field detection applied to embedded magnetic shape memory alloy (MSMA) is demonstrated both experimentally and using computational models. A concrete beam containing iron-based MSMA wire is subjected to a 3-point bend test where structural damage is induced, thereby 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. Additionally, the implementation of stranded MSMA cables in place of the MSMA wire is assessed through similar computational models. The combination of these computational models and their subsequent experimental validation provide sufficient support for the feasibility of SHM using magnetic field sensing via MSMA embedded components.

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