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Top1. Introduction
In last few decades, smart structures have gained tremendous popularity among the researchers for its application in vibration control and damage compensation capability. These smart structures can be considered as the structure having several distributed sensors and/or actuators (Lee C. K. and Moon F. C,1990)made of piezoelectric materials such as lead zirconatetitanate (PZT) and polyvinylidene fluoride (PVDF). However, due to environment perspective, efforts have now been shifted towards lead free piezoelectric materials. Nevertheless, piezo-ceramics such as PZT are still being used due to their effective electromechanical properties. Energy harvesting and repair of cracks on structural elements using such piezoelectric sensors and actuators are one of the active areas of research in last few years.
Several ideas have been proposed in order to shape and design the portable electronic devices where battery size is a limiting factor. In this regard, use of piezoelectric sensors have gained popularity as it can be used as electrical energy harvesters drawing energy from vibrating or deformed structural elements. There have been continuous efforts to reduce the power requirements for microelectronic devices by using the environmental energy sources to meet these requirements in wearable devices. Use of piezoelectric harvesters is not limited to wireless portable electronic or small wearable devices.(Starner T,1996; Matsuzawa K. and Saka M, 1997; Kymissis J., Kendall K., Paradiso J. and Gershenfeld N, 1998) and It’s uses have been extended in various civil structures as well, where finite life cycle of batteries are being replaced by such harvesters for prolonged and continuous power supply. (Sadano H. A., Park G. and Inman D. J,2004; Mineto A. T., Braun M. P. S, Navarro H. A. and Varoto, 2010)
Energy harvesting capabilities of such piezoelectric materials are also used by various researchers to explore potential areas of application. Crack detection and repair in a dynamically or statically loaded structural element using piezoelectric patch is one of the key areas of research in recent times.Crack modeling and analysis of static and dynamic response of such damaged structures have been investigatedby various authors.(Panigrahi B. and Pohit,2016 ; Kitipornchai S., Ke L. L., Yang J. and Xiang,2009; Panigrahi B. and Pohit G,2010;Panigrahi B. and G. Pohit, 2018) . (Yin L., Wang X. and Shen Y,1996) Proposed a strain based method for possible damage detection of composites using PVDF. (Fukunaga H., Hu N. and Chang F, 2002), proposed a crack identification method using piezoelectric sensors and subsequently an iterative method to quantify the crack severity. (Zhang R,2011) studied the free vibration response of a cracked FGM beams with piezoelectric patch. (Afshari M. and Inman D,2013) proposed a crack beam model integrated with the piezoelectric patch considering the energy loss due to crack.(Patil C. S., Roy S. and Jagtap K. R,2017) proposed a finite element method to detect the flaw such as bolt loosening effects on framed structures using piezoelectric materials. (Vitola J., Pozo F., Tibaduiza D. A. and Anaya M, 2017) investigated the damage identification process in structures applied to thermal loading using piezoelectric sensors. (Chomette B.,Fernandes A. and Sinou J.-J., 2013)introduced an innovative method to locate cracks by employing piezoelectric materials. The creativity of the anticipated strategy is to develop the verity that the modal control is modest. The key idea of the control system is at this juncture to identify cracks. A new method is proposed by (Shengjie Z., Nan W. and Quan W., 2017) to detect crack in structural element e.g. beam by using piezoelectric sensor/actuator. The piezoelectric patches are in use to produce an excitation following the feedback to alter the stiffness at the position of crack leading to change in natural frequency gets enhanced. (Fangxin Z., Aliabadi M. H, 2015) detected the size of the cracks on isotropic plates. The Lamb waves detection signals are generated and received by using piezoelectric transducers. (Sinyeob L., Seongbin J. and Junhong P., 2013) carried out a crack detection technique to monitor structural health by vibrational analysis, where the excitation is generated with the aid of piezoelectric transducers. They observed that any kind of damage in structure effects to the character of the propagation of flexural wave due to changes in properties of structure.