Corrosion induced thickness loss of metallic structures is one of the most common issues across multiple industries. In our previous work, a new type of corrosion sensor based on lead zirconate titanate (PZT) using electromechanical impedance (EMI) technique was proposed. The sensor is fabricated by bonding a PZT patch onto a metal plate. The previous work has demonstrated that the peak frequencies in the conductance signatures decrease linearly with the increase of the corrosion induced thickness loss. However, a theoretical model that fully describe the coupled vibration between piezoelectric element and the metal plate, and the EMI characteristics has not been established. This paper presents the theoretical modeling of the EMI instrumented circular piezoelectric-metal transducer for corrosion monitoring purpose. Based on electro-elastic and Kirchhoff plate theory, the EMI responses of the transducer operated in transverse bending modes with free boundary conditions were modeled. Finite element modeling calculations and experimental measurement were conducted to validate the theoretical results with good agreement.

Corrosion of metallic structures widely existed in multiple industries, such as oil and gas, civil infrastructure, aerospace, mechanical, mining, and processing. Current available corrosion-monitoring methods are based on different sensing principles, which have their own advantages, and some drawbacks that may limit their application on some aspects. This article presents an electromechanical impedance-instrumented corrosion-measuring probe for corrosion monitoring. The proposed probe is fabricated by attaching a circular lead zirconate titanate patch onto a metal rod. Compared to other electromechanical impedance-based corrosion-monitoring methods, the probe is capable of isolating the influence of structural complexity, variations in loading and boundary conditions. Five probes were fabricated in the experimental study and three of them were subjected to accelerated corrosion tests to mimic the corrosion-induced mass loss damage. Results showed that the peak magnitude of the conductance signatures was reduced with the increase in corrosion amount. The variations in the conductance signatures were quantified by three statistical quantifying metrics, that is, root-mean-square deviation, mean absolute percentage deviation, and correlation coefficient deviation. All these metrics increase with the increase in corrosion amount, which can be used as an indicator of the corrosion process. This study proves that the proposed corrosion-measuring probe is effective in monitoring corrosion and shows promising application potential. This research also serves as a proof-of-concept study to demonstrate the capability of the electromechanical impedance technique in monitoring mass loss due to corrosion.

Capturing vibration energy of track structures using piezoelectric energy harvesters has attracted increasing attention for powering wireless sensor networks along railway line. To better use the vertical space below steel rail, a kind of piezoelectric tube stack energy harvesters is proposed in this paper, which can be placed at the bottom of the steel rail to harvest the vibration energy of the vertical displacement induced by the moving train. The harvester consists of a displacement transmission rod, a compression spring, a force transmission metal tube, a piezoelectric tube stack, a whole metal shell, screw bolts, and a wire hole. The advantage of this design is to fully combine the heights of the compression spring, the force transmission metal tube and the piezoelectric tube stack, which helps reduce the vertical height of the device and enables its wide application to a variety of tracks, including, ballast track, ballastless track, and steel-spring floating slab track. Energy harvesting performance of the developed piezoelectric tube stack energy harvester is investigated experimentally, which is consistent with the theoretical results of the simplified model of such a harvester reported. Effects of displacement amplitude, displacement frequency, spring stiffness, resistance, and key parameters of piezoelectric tube stack on the energy harvesting performance of the harvester are also discussed. The present study provides a new design concept for developing piezoelectric energy harvesters used in railway systems with the smaller vertical space below steel rail.

Cracks will inevitably occur in concrete structures or members during the construction process and service life due to aging, environmental factors, external loads, etc. To improve the strength and stability of the cracked concrete structures, many methods have been proposed to repair the cracks. However, the monitoring of the repairing process and repair quality has not been fully studied. The previous studies have proved that the spherical smart aggregates (SSAs) based on the electromechanical impedance (EMI) technique have outperformed the traditional smart aggregates (SAs) based on the EMI technique in structural health monitoring of civil structures, however, SSAs have not been applied to the monitoring of the concrete crack repair. In this work, the monitoring of the concrete crack repair using the SSAs based on the EMI technique was explored. A total of eight concrete specimens were prepared, and cracks in the concrete specimens were simulated by manually cutting under laboratory conditions. According to the principle of grouting method, two repair agents including cement paste and cement mortar were used to repair the cracks. The impedance signals of 28 d were measured, and three quantitative indicators, namely root mean square deviation, mean absolute percentage deviation, and correlation coefficient deviation were used to evaluate the quality of the concrete repair effect. The results indicate that the SSAs show excellent sensitivity and stability over the traditional SAs. In addition, the normalized values of the quantitative indicators were analyzed to distinguish the types of repair agents. A mathematical expression of exponential function was also proposed by fitting the experimental data to quantitatively evaluate and predict the repair effect of concrete cracks. Further, the influences of temperature, humidity, crack depth and width on the experimental results were analyzed and discussed. The numerical simulation was also presented to validate the reasonability of the experimental results.

This paper presents the dynamic analytical solution of a piezoelectric stack utilized in an actuator and a generator based on the linear piezo-elasticity theory. The solutions for two different kinds of piezoelectric stacks under external load were obtained using the displacement method. The effects of load frequency and load amplitude on the dynamic characteristics of the stacks were discussed. The analytical solutions were validated using the available experimental results in special cases. The proposed model is able not only to predict the output properties of the devices, but also to reflect the inner electrical and mechanical components, which is helpful for designing piezoelectric actuators and generators in a comprehensive manner.