Applications of Piezoelectric Materials in Structural Health Monitoring and Repair: Selected Research Examples

The research presented in this thesis develops a new methodology for the structural health monitoring of structures. The methodology is based on the use and the application of smart materials and specifically the piezoelectric materials (lead zirconate titanate PZT). These materials are installed and applied in the concrete members of a structure. Therefore, the specific characteristics of the PZTs in combination with their interaction with the structure are used in order to develop the new health monitoring technique. Physical changes in the structure cause changes in the structural mechanical impedance. Due to electromechanical coupling between the piezoelectric material and the structure, the change in structural mechanical impedance induces a change in the electrical impedance of the piezoelectric material. The proposed methodology is based on the interaction of PZT with the structure according to the Electro-Mechanical Impedance EMI or its inverse Electro-Mechanical Admittance EMA. The methodology uses the electromechanical data in frequency response with statistical techniques to damage detection. This includes two stages, in first stage the detection of damage, and if provided that this exists, in second stage the location and level of the damage. Since the widespreadest building material in the existing structures is concrete, the examined numerical application of the proposed methodology is a concrete structural element. The well-known strengthening technique of deficient concrete members using epoxy bonded Fibre Reinforced Polymer (FRP) materials is used herein in order to examine the application of smart materials and the proposed methodology in a FRP concrete component. These composite materials have experienced a continuous increase of use in structural strengthening and repair applications around the world in the last decade. High stiffness-to-weight and strength-to-weight ratios of these materials combined with their superior environmental durability have made them a competing alternative to the conventional strengthening and repair materials. From a structural mechanics point of view, an important concern regarding the effectiveness and safety of this method is the potential of brittle and premature failures due to the debonding of the FRP materials. Such failures, unless adequately considered in the design process, may significantly decrease the effectiveness of the strengthening. In this thesis, a new method that prevents FRP debonding using smart piezoelectric materials is investigated. The technique consists of the installation of system of piezoelectric (sensor - actuator) at the edge of the epoxy bonded FRP to the concrete member. The application of this system in combination with a specific optimisation method that is based on the EMA response of PZT, can produce controlled local forces and moments with opposite effect to that of a harmonic load at the middle of the beam. These forces are capable to reverse and to compensate the imminent debonding of the edge of the FRP which are based on a new repair criterion. Using the proposed method, the control of the FRP debonding in a concrete member under dynamic loading is achieved. Further, a special criterion for the “active” repair of the continuous contact between FRP and concrete is proposed. Thus, the application method of a “smart and readjusted FRP” for the repair of FRP concrete components under dynamic load is developed. Achieve The effectiveness of the proposed method is analytically investigated using the finite element program COMSOL (former FEMLAB) for the simulation of the smart structural system. The statistical process of the EMA response data and the development of the proposed optimisation methods are achieved using MATLAB environment developed for the purposes of this study.

Piezoelectric materials have become the most attractive functional materials for sensors and actuators in smart structures because they can directly convert mechanical energy to electrical energy and vise versa. They have excellent electromechanical coupling characteristics and excellent frequency response. In this article, the research activities and achievements on the applications of piezoelectric materials in smart structures in China, including vibration control, noise control, energy harvesting, structural health monitoring, and hysteresis control, are introduced. Special attention is given to the introduction of semi-active vibration suppression based on a synchronized switching technique and piezoelectric fibers with metal cores for health monitoring. Such mechanisms are relatively new and possess great potential for future applications in aerospace engineering.

The application of piezoelectric impedance principle in health monitoring of civil engineering structures has attracted more and more attention. In this paper, the application of piezoelectric materials in health detection of civil engineering structures is reviewed. The basic principles, research progress, advantages and problems of impedance method and wave method are analyzed. Civil engineering structures, such as dams, bridges, high-rise buildings, etc., will inevitably suffer some damage during their service. Sometimes it is caused by natural factors of force majeure, or due to long-term accumulation damage, these damages will directly cause structural resistance to decay, and in severe cases may lead to catastrophic accidents. The support role of structural monitoring technology is needed to provide early warning of these disasters. Piezoelectric materials, piezoelectric impedance principles, interaction models of piezoelectric materials with monitored structures, and monitoring techniques based on impedance information. The research results of piezoelectric material size selection, scanning frequency selection, sensing range, binder influence, data acquisition equipment development and data processing methods are summarized.

A spacecraft's hull has an upper limit on the amount of deformation it can withstand due to accelerating forces, a limitation often defined by the hull's composite material's Young's Modulus. This upper limit on the tensile and compressive forces that deform the material beyond its breaking point can be elevated with a modified Young's Modulus through the application of a piezoelectric material. When a section of the hull composed of the piezoelectric material holding a baseline electric charge undergoes deformation due to an external force, a voltage differential is created with the surrounding sections that is directly proportional to the degree of deformation. A new equilibrium for the hull's deformation is created through a back-current, a process that counteracts the initial deformation and therefore voltage differential with an equal and opposite change in voltage. This entire process is controlled by circuitry that both detects the hull's voltage differential and regulates current to and from the hull to counteract its deformation. This paper designs the hull's new architecture and provides the mathematical formulism to calculate its modified Young's Modulus and the resulting critical acceleration it can undergo.

Influence of interface and strain hardening cementitious composite (SHCC) properties on the performance of concrete repairs

While many new smart materials have been developed over the last few years, the integration of these materials into useful systems must be exploited if this emerging technology is to become viable. Two applications of piezoelectric and electrostrictive materials are proposed that generate both micro and macro positioning control. Additionally, an overview of these smart materials and their properties is given. Precise micro positioning devices have applications to adaptive optical systems. A NASA project called Space Laser Energy (SELENE) involves such a system. This project proposes to control the surface of a power transmission dish comprised of several thousands of small lenses or lenslets. A major objective of the dish is to increase efficiency by compensating for atmospheric disturbances. A second application of piezoelectric materials is presented for micro and macroscopic one dimensional motion. Specifically, a novel design of an inchworm device is presented. This device has the ability to generate macroscopic motion from microscopic piezoelectric expansions and contractions, the frequency of these expansion/contraction cycles should allow the motor to move for significant distances as well as provide incremental micro positioning.

This review focuses on vibrating beam structures with different constraints. The review is also aimed to analyse the different fault detection approaches for condition monitoring of cracks in vibrating structures. The advancement in this field with significant and diversified techniques namely analytical, numerical and experimental approaches are elaborated and presented here. The significance of crack location and the severe effects on the responses of the vibrating structure are discussed. The application of piezoelectric material on structures, as well as different fault detection and soft computing techniques are summarized to monitor the conditions of a structure. A concise review study has also been conducted for better improvement in the service period. The integrity of the structure can be improved with the aid of vibration control and Structural Health Monitoring (SHM) approaches.

Smart materials and structures are inspired in nature and try to mimic adaptive characteristics of natural systems. In brief, it is possible to say that smart materials have special properties that couple mechanical and non-mechanical fields, conferring adaptive characteristics. Smart systems and structures use this kind of material as sensors and actuators. In general there are four major groups of smart materials: piezoelectric, shape memory alloys, magnetostrictive materials, electro-magneto rheological fluids. Nowadays, several fields of science and technology are exploiting the remarkable properties of smart systems and structures including bioengineering, aerospace engineering, robotics and vibration/shape control. Therefore, several applications have been developed, giving the increasing importance to this kind of system. In order to consolidate this new design paradigm in Brazil, several research groups from different Brazilian Universities and also international partners created the National Institute of Science and Technology of Smart Structures in Engineering (INCT-EIE) . Moreover, the Brazilian community created the Committee of Smart Materials and Structures of the Brazilian Society of Mechanical Sciences and Engineering (M&EInt/ABCM) . In order to celebrate the consolidation of this area in Brazil, we are producing this Special Issue on Smart Materials and Structures of the Journal of the Brazilian Society of Mechanical Sciences and Engineering. This special issue presents a general overview of the activities of the Brazilian community together with the international partners. Applications of piezoelectric materials and shape memory alloys are mainly discussed in the contributions. Kalamkarov and Savi (2012) presented a review of micromechanical modeling of smart composite structures reinforced by a periodic grid that can exhibit piezoelectric behavior. The asymptotic homogenization is employed. Trindade and Benjeddou (2012) developed a parametric analysis of effective material properties of thickness-shear piezoelectric macro-fibre composites. Finite element homogenization method is employed evaluating the influence of several parameters on material properties. Medeiros et al. (2012) presented a procedure to evaluate effective properties on smart composite materials with piezoelectric fibers. Finite element method is applied for unidirectional periodic piezoelectric composites. Nitzsche (2012) discussed the realization of semi-active actuators employed for application in structural control. The general idea is applied for an actuator using piezoelectric material as adaptive material. Motter et al. (2012) discussed vibration-based energy harvesting employing piezoelectric materials. Different rectifier circuits are of concern, analyzing numerical and experimental results. Abreu et al. (2012) presented a discussion about active vibration control of a cantilever beam using a model-based digital controller and piezoelectric sensor and actuators. The main focus of the paper is the design of the controller, showing experimental results that assure its efficacy. Martins et al. (2012) treated the structural health monitoring for aeronautical applications by using piezoelectric materials. Electromechanical impedance measures are employed to perform nondestructive inspection. The paper discussed a case study of an aluminum aircraft window with satisfactory results. De Paula et al. (2012) investigated the nonlinear dynamics of large-scale space structures with embedded shape memory alloy actuators. The investigation considered an archetypal model composed of a single mass connected by SMA elements. This system has a complex behavior including chaos. The paper discussed some aspects of the system dynamics giving special attention for the influence of geometrical imperfections. Lima et al. (2012) discussed the control of a beam using shape memory alloys as actuators. A PI controller is employed to an experimental rig showing its applicability for the deformation control.

Piezoelectric materials have become the most attractive functional materials for sensors and actuators in smart structures because they can directly convert mechanical energy to electrical energy and vise versa. They have excellent electromechanical coupling characteristics and excellent frequency response. In this article, some research activities on the applications of piezoelectric materials in smart structures, including semi-active vibration control based on synchronized switch damping using negative capacitance, energy harvesting using new electronic interfaces, structural health monitoring based on a new type of piezoelectric fibers with metal core, and active hysteresis control based on new modified Prandtl-Ishlinskii model at the Aeronautical Science Key Laboratory for Smart Materials and Structures, Nanjing University of Aeronautics and Astronautics are introduced.

The repair and strengthening of reinforced concrete members are very important due to several factors, including unexpected increases in load levels and/or the damaging impact of aggressive environmental conditions on structural concrete members. Many researchers have turned to using materials for the repair and strengthening of damaged structures or the construction of new concrete structural members. Ultrahigh‐performance fibre‐reinforced concrete (UHPFRC), characterized by superior structural and durability performance in aggressive environmental conditions, is one of the materials that have been considered for the repair and strengthening of concrete structural members. The repair or strengthening of concrete structures using UHPFRC needs a thorough knowledge of the behaviour of both the strengthening material and the strengthened concrete structure at service load conditions, in addition to an understanding of the design guidelines governing the use of such materials for effective repair and strengthening. In this study, the recent issues and findings regarding the use of UHPFRC as a repair or strengthening material for concrete structural members are reviewed, analysed, and discussed. In addition, recommendations were made concerning areas where future attention and research on the use of UHPFRC as a strengthening material needs to be focused if the material is to be applied in practice.

The development of ultrasonic motors is a highlight in the application of piezoelectric materials. Ultrasonic motors take advantage of converse piezoelectricity of piezoelectric materials to yield mechanical output from converting electrical energy. It is no doubt that piezoelectric materials are in the central position that controls the performance of the devices. In this chapter, we will review piezoelectric materials and their properties from the aspect of their applications in ultrasonic motors. The chapter begins with a brief overview of historical development of piezoelectric materials, and then a detailed explanation of the electrical and mechanical properties of piezoelectric materials will be discussed in the second and the third sections, where the piezoelectric constitutive equations are specially stressed. Piezoelectric vibrators, as basic units of piezoelectric devices, and their vibration types will be described in sequence. In the last two sections, the application of piezoelectric materials in ultrasonic motors and some advances in novel materials will be introduced.

Fabrication and induced mineralization of bio-piezoelectric ceramic coating on titanium alloys

The potential of piezoelectric ceramics on repair of delaminated structures subjected to a static loading is re- searched in the letter. A sliding fracture mode on two tips of a delaminated beam structure was uncovered by the author in a previous report. The stress singularity due to the fracture mode at the tips is attempted to be mended with a pair of pie- zoelectric patches by virtue of their electro-mechanical characteristics. A developed mechanics model is employed to study the applicability of the piezoelectric materials in repairing four types of delaminated structures, i.e. simply sup- ported, cantilevered, propped cantilevered, and fixed beams. The effectiveness of the proposed method is particularly in- vestigated with respect to the locations of the delamination in both the thickness and longitudinal directions of the beams. It is hoped that the research findings in the letter will promote an application of smart materials to repair delaminated or cracked engineering structures. beam subjected to static loading via piezoelectric patches. Wang and Quek (9) developed a simple mechanics model for repair of delaminated beams subjected to concentrated static loading via piezoelectric patches. Their analysis exposed that sliding mode fracture is induced at the tips of the delamina- tion, leading to stress singularity. A simple repair methodol- ogy via piezoelectric patches was attempted to remove this singularity. However, a slight opening fracture mode may be stimulated from the model which was found recently by the author's group. Duan et al. (10) proposed a finite element analysis on repair of a delaminated simply supported beam structure via piezoelectric materials. Results on the effect of the delamination locations, external loading locations, and the length of piezoelectric patches on the effectiveness of the piezoelectric materials were summarized for the specific delaminated structure with pin ends.

In this paper, a comprehensive review of nanostructures that exhibit piezoelectric behavior on all mechanical, buckling, vibrational, thermal and electrical properties is presented. It is firstly explained vast application of materials with their piezoelectric property and also introduction of other properties. Initially, more application of material which have piezoelectric property is introduced. Zinc oxide (ZnO), boron nitride (BN) and gallium nitride (GaN) respectively, are more application of piezoelectric materials. The nonlocal elasticity theory and piezoelectric constitutive relations are demonstrated to evaluate problems and analyses. Three different approaches consisting of atomistic modeling, continuum modeling and nano-scale continuum modeling in the investigation atomistic simulation of piezoelectric nanostructures are explained. Focusing on piezoelectric behavior, investigation of analyses is performed on fields of surface and small scale effects, buckling, vibration and wave propagation. Different investigations are available in literature focusing on the synthesis, applications and mechanical behaviors of piezoelectric nanostructures. In the study of vibration behavior, researches are studied on fields of linear and nonlinear, longitudinal and transverse, free and forced vibrations. This paper is intended to provide an introduction of the development of the piezoelectric nanostructures. The key issue is a very good understanding of mechanical and electrical behaviors and characteristics of piezoelectric structures to employ in electromechanical systems.

We have described four important applications for piezoelectric materials in the oilfield services industry. High piezoelectric coupling materials are always sought after in developing our devices. However the high coupling materials invariably are ceramics-based and they tend to operate at a disadvantage into a liquid medium in terms of efficiency and bandwidth. Solutions exist to address these problems, such as matching layers and composite materials. But they pose extra complications in a harsh operating environment. It would be desirable to have a high-coupling, low-impedance piezoelectric materials as additional choices. As the industry ventures into ever-deeper and hotter wells, new high-coupling, and higher Curie temperature materials would be required.