Electrical Impedance Tomography-based Sensing Skin for Structural Health Monitoring

2015 ◽  
Author(s):  
MILAD HALLAJI ◽  
AKU SEPPANEN ◽  
MOHAMMAD POUR-GHAZ
Keyword(s):  
Structural Health Monitoring ◽  
Electrical Impedance Tomography ◽  
Health Monitoring ◽  
Electrical Impedance ◽  
Impedance Tomography ◽  
Structural Health ◽  
Sensing Skin

On the inverse determination of displacements, strains, and stresses in a carbon nanofiber/polyurethane nanocomposite from conductivity data obtained via electrical impedance tomography

2017 ◽  
Vol 28 (18) ◽  
pp. 2617-2629 ◽  
Author(s):  
TN Tallman ◽  
S Gungor ◽  
GM Koo ◽  
CE Bakis
Keyword(s):  
Structural Health Monitoring ◽  
Electrical Impedance Tomography ◽  
Health Monitoring ◽  
Electrical Impedance ◽  
Carbon Nanofiber ◽  
Constitutive Relations ◽  
Full Potential ◽  
Conductivity Data ◽  
Impedance Tomography ◽  
Structural Health

Carbon nanofiller-modified composites possess extraordinary potential for structural health monitoring because they are piezoresistive and therefore self-sensing. To date, considerable work has been done to understand how strain affects nanocomposite conductivity and to utilize electrical impedance tomography for detecting strain or damage-induced conductivity changes. Merely detecting the occurrence of mechanical effects, however, does not realize the full potential of piezoresistive nanomaterials. Rather, knowing the mechanical state that results in the observed conductivity changes would be much more valuable from a structural health monitoring perspective. Herein, we make use of an analytical piezoresistivity model to inversely determine the displacement field of a strained carbon nanofiber/polyurethane nanocomposite from conductivity changes obtained via electrical impedance tomography. From the displacements, kinematic and constitutive relations are used to calculate strains and stresses, respectively. A commercial finite element simulation is then used to validate the accuracy of these predictions. These results concretely demonstrate that it is possible to inversely determine displacements, strains, and stresses from conductivity data thereby enabling unprecedented insight into the mechanical response of piezoresistive nanofiller-modified materials and structures.

scholarly journals Evaluation of the Damage Detection Characteristics of Electrical Impedance Tomography

2013 ◽  
Author(s):  
Bryan R. Loyola ◽  
Luciana Arronche ◽  
Marianne LaFord ◽  
Valeria La Saponara ◽  
Kenneth J. Loh
Keyword(s):  
Thin Film ◽  
Electrical Conductivity ◽  
Carbon Nanotube ◽  
Electrical Impedance Tomography ◽  
Health Monitoring ◽  
Electrical Impedance ◽  
Fiber Reinforced Polymer ◽  
Impedance Tomography ◽  
Structural Health ◽  
Reinforced Polymer

In the United States, many civil, aerospace, and military aircraft are nearing the end of their service life. Many of these service life predictions were determined by models that were created at the time of the design of the structure, possibly decades ago. As a precaution, these structures are inspected on a regular basis with techniques that tend to be expensive and laborious, such as tear-down inspections of aircraft. To complicate matters, new complex materials have been incorporated in recent structures to take advantage of their desirable properties, but these materials sustain damage in a manner that is different from that of past monolithic materials. One example is fiber-reinforced polymer (FRP) composites, which are heterogeneous, direction-dependent, and tend to manifest damage internal to their laminate structure, thus making the detection of this damage nearly impossible. For these reasons, numerous groups have focused on developing sensors that can be applied to or embedded within these structures to detect this damage. Some of the most promising of these approaches include using piezoelectric materials as passive or active ultrasonic sensors and actuators, fiber optic-based sensors to measure strain and detect cracking, and carbon nanotube-based sensors that can detect strain and cracking. These are mostly point-based sensors that are accurate at the location of application but require interpolative methods to ascertain the structural health elsewhere on the structure. To conduct direct damage detection across a structure, we have coupled the ability to deposit a carbon nanotube thin film across large substrates with a spatially distributed electrical conductivity measurement methodology called electrical impedance tomography. As indicated by previous research on carbon nanotube thin films, the electrical conductivity of these films changes when subjected to strain or become damaged. Our structural health monitoring strategy involves monitoring for changes in electrical conductivity across an applied CNT thin film, which would indicate damage. In this work, we demonstrate the ability of the Electrical Impedance Tomography (EIT) methodology to detect, locate, size, and determine severity of damage from impact events subjected to glass fiber-reinforced polymer composites. This will demonstrate the value and effectiveness of this next-generation structural health monitoring approach.

A functionally layered sensing skin for the detection of corrosive elements and cracking

2016 ◽  
Vol 16 (2) ◽  
pp. 215-224 ◽  
Author(s):  
Aku Seppänen ◽  
Milad Hallaji ◽  
Mohammad Pour-Ghaz
Keyword(s):  
Reinforced Concrete ◽  
Structural Health Monitoring ◽  
Health Monitoring ◽  
Electrical Impedance ◽  
The Other ◽  
Reinforced Concrete Structures ◽  
Impedance Tomography ◽  
Sensing System ◽  
Surface Sensing ◽  
Sensing Skin

In this paper, we propose an electrical impedance tomography (EIT)-based multifunctional surface sensing system, or sensing skin, for structural health monitoring. More specifically, the EIT-based sensing skin is developed for detecting and localizing the ingress of chlorides and cracking: two phenomena which are of concern in many structures, including reinforced concrete structures. The multifunctional sensing skin is made of two layers: one layer is sensitive to both chlorides and cracking, and the other layer is sensitive to cracking only. In the experiments, the sensing skin is tested on a polymeric and concrete substrate. The results demonstrate the feasibility of using the multifunctional multi-layer sensing skin for detecting and localizing corrosive elements and cracking, and for distinguishing between them.

Experimental and theoretical analysis in impedance-based structural health monitoring with varying temperature

2010 ◽  
Vol 10 (6) ◽  
pp. 573-585 ◽  
Author(s):  
Naserodin Sepehry ◽  
Mahnaz Shamshirsaz ◽  
Ali Bastani
Keyword(s):  
Structural Health Monitoring ◽  
Health Monitoring ◽  
Electrical Impedance ◽  
Electromechanical Coupling ◽  
Coupling Effect ◽  
Physical And Mechanical Properties ◽  
Measurement Tool ◽  
Temperature Dependent ◽  
Structural Health ◽  
Aluminum Alloy 2024

In the recent years, the piezoelectric wafer active sensors (PWASs) are increasing as a measurement tool in structural health monitoring techniques. In impedance-based structural health monitoring (ISHM) method, the electrical impedance of a PWAS bonded to the structure is measured and served as a defect detection index of the structure. The principle of this method is based on the electromechanical coupling effect of PWAS materials. As any change in the structure will lead to a change in mechanical impedance of structure, the electrical impedance of PWAS could sense this change by the electromechanical coupling effect of PWAS. Since the physical and mechanical properties of PWAS materials are temperature-dependent, so the electrical impedance of PWAS will change with varying temperature. Consequently, the changes in environmental or service temperatures could be detected in ISHM method as a defect. In this article, in order to consider the temperature dependency of PWAS material properties, a temperature-dependent model is developed for a PWAS bonded to an Euler Bernoulli cantilever beam. An aluminum (alloy 2024) beam was examined experimentally by ISHM method in order to validate the proposed model. The comparison of theoretical and experimental results demonstrates a good improvement in ISHM modeling where temperature variation is present.

Electromechanical Impedance Modeling for Structural Health Monitoring

2012 ◽  
Author(s):  
Liuxian Zhao ◽  
Lingyu Yu ◽  
Mattieu Gresil ◽  
Michael Sutton ◽  
Siming Guo
Keyword(s):  
Structural Health Monitoring ◽  
Health Monitoring ◽  
Electrical Impedance ◽  
Piezoelectric Materials ◽  
Fiber Composite ◽  
Mechanical Impedance ◽  
Experimental Result ◽  
Electromechanical Impedance ◽  
Structural Health ◽  
Aluminum Beam

Electromechanical impedance (EMI) method is an effective and powerful technique in structural health monitoring (SHM) which couples the mechanical impedance of host structure with the electrical impedance measured at the piezoelectric wafer active sensor (PWAS) transducer terminals. Due to the electromechanical coupling in piezoelectric materials, changes in structural mechanical impedance are reflected in the electrical impedance measured at the PWAS. Therefore, the structural mechanical resonances are reflected in a virtually identical spectrum of peaks and valleys in the real part of the measured EMI. Multi-physics based finite element method (MP-FEM) has been widely used for the analysis of piezoelectric materials and structures. It uses finite elements taking both electrical and mechanical DOF’s into consideration, which allows good differentiation of complicated structural geometries and damaged areas. In this paper, MP-FEM was then used to simulate PWAS EMI for the goal of SHM. EMI of free PWAS was first simulated and compared with experimental result. Then the constrained PWAS was studied. EMI of both metallic and glass fiber composite materials were simulated. The first case is the constrained PWAS on aluminum beam with various dimensions. The second case studies the sensitivity range of the EMI approach for damage detection on aluminum beam using a set of specimens with cracks at different locations. In the third case, structural damping effects were also studied in this paper.. Our results have also shown that the imaginary part of the impedance and admittance can be used for sensor self-diagnosis.

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