IJSRD - International Journal for Scientific Research & Development| Vol. 5, Issue 10, 2017 | ISSN (online): 2321-0613 All rights reserved by www.ijsrd.com 99 Non Destructive Evaluation and Structural Health Monitoring: A Review Ms. A. A. Shelke Assistant Professor Shri Chhatrapati Shivajiraje College of Engineering, Dhangawadi Bhor, Pune, Maharashtra, India Abstract— Structural health monitoring has great potential for enhancing the functionality, serviceability and increased life span of structures. Structural health monitoring is defined as “continuous, autonomous, real time, in-service monitoring of the physical condition of a structure by means of embedded or attached sensors with minimum manual intervention". This need which arises from the fact that intensive usage combined with long endurance causes gradual but unnoticed deterioration in structures, often leading to unexpected disasters. Recently smart piezoelectric-ceramic lead material is emerged as high frequency impedance transducers for non- destructive evaluation. In this role, the PZT patches act as collocated actuators and sensors and employ ultrasonic vibrations gives a characteristic admittance ‘signature’ of the structure. The admittance signature has vital information about the nature of the structure, and it can be analysed to predict the onset of structural damages. PZT patches exhibit excellent performance as far as damage sensitivity. Their sensitivity is high enough to capture any structural damage at the incipient stage. There are different Non-Destructive techniques like acoustic emission, ultrasonic, acousto- ultrasonic, guided ultrasonic waves or Lamb waves. The Lamb wavebased active SHM method uses piezoelectric (PZT) sensors to transmit and receive wave. Thus, Lamb waves generated by PZT sensors and time-frequency analysis techniques could be used effectively for damage detection. This study has given a complete idea of the working and the basic requirements of SHM system. Key words: Structural Health Monitoring (SHM), Nondestructive Evaluation (NDE), PZT Patches, Lamb Waves I. INTRODUCTION Structural health monitoring provides the ability of a system to detect adverse changes within a system’s structure. SHM is an emerging technology that has multiple applications. Development of new techniques for structural health monitoring (SHM) and non-destructive evaluation (NDE) is need arises from the fact that intensive usage combined with long endurance causes gradual but unnoticed deterioration in structures, often leading to unexpected disasters. In this PZT materials, for example, have recently emerged as high frequency impedance transducers for SHM and NDE. In this role, the PZT patches act as collocated actuators and sensors and employ ultrasonic vibrations gives a characteristic admittance ‘signature’ of the structure. With the increasing number of civil structures, it has become a necessity to monitor these structures regularly via Non-destructive Testing/ Structural Health Monitoring methods, to prevent catastrophic failures. Also it is required to implement cost- effective measures and ease of implementation. This way the cost gets reduced as it minimizes maintenance and inspection cycles. II. REVIEW OF LITERATURE A. Nishanth R. and Maheshprabhu.R, et.all [1] Has carried out study on structural health monitoring which is based on Lamb wave propagation. It has been developed especially for distinguishing different kinds of damages. The Lamb wave-based active SHM method uses piezoelectric (PZT) sensors to transmit and receive Lamb waves in a thin Aluminium plate. The Lamb wave modes travel into the structure and are reflected by the structural boundaries, discontinuities, and damage. By studying their propagation and reflection, the presence of defect in the structure is determined. Laboratory level experiments have been carried out on thin Aluminium plates with angular, horizontal and vertical defect. This study provides significant insight into the problem of identifying localized damages in the structure using PZT and dispersion of signal after they interact with different types of damage. Those small defect like the horizontal one that may be nearly missed in time domain analysis can also be clearly identified in the STFT analysis. Moreover the occurrence of so mode is also clearly seen. Thus, Lamb waves generated by PZT sensors and time- frequency analysis techniques could be used effectively for damage detection in aluminium plate. B. Hui-Ru Shih, Wilbur L. Walters et. all [2] Has carried out study on structural health monitoring (SHM) is an emerging technology that has multiple applications. SHM emerged from the wide field of smart structures, and it also encompasses disciplines such as structural dynamics, materials and structures, non-destructive testing, sensors and actuators, data acquisition, signal processing, and possibly much more. C. Dr. Suresh Bhalla and Chee-Kiong Soh [3] has carried out study on development of new techniques for structural health monitoring (SHM) and non-destructive evaluation (NDE) is need arises from the fact that intensive usage combined with long endurance causes gradual but unnoticed deterioration in structures, often leading to unexpected disasters. In this smart piezoelectric-ceramic lead zirconate titanate (PZT) materials, for example, have recently emerged as high frequency impedance transducers for SHM and NDE. In this role, the PZT patches act as collocated actuators and sensors and employ ultrasonic vibrations (typically in 30-400 kHz range) to glean out a characteristic admittance ‘signature’ of the structure. The admittance signature encompasses vital information governing the phenomenological nature of the structure, and can be analysed to predict the onset of structural damages. As impedance transducers, the PZT patches exhibit excellent performance as far as damage sensitivity and cost- effectiveness are concerned. Typically, their sensitivity is high enough to capture any structural damage at the incipient stage, well before it acquires detectable macroscopic