Singly Curved Thin Piezo Transducers for Energy Harvesting and Structural Health Monitoring, Edition 1

Piezoelectric materials have secured a significant place in the field of structural health monitoring (SHM) and vibration energy harvesting over the past two decades. Although these materials are available in several forms and configurations, the efficacy of curved configurations is still unexplored. This study investigates, both experimentally and numerically, the potency of the curved configuration of the piezo transducers over the straight configuration when embedded in reinforced concrete (RC) structures for vibration energy harvesting and SHM. This book, based on the M.Tech thesis of the lead author completed in the Department of Civil Engineering at IIT Delhi, covers the comparative analysis of (a) open-circuit voltage generated across the piezo transducers; (b) the power developed under the impedance matching conditions; and (c) the potential of power storage into capacitors for both configurations. The book also experimentally examines the hitherto unexplored damage detection capability of the curved piezo transducers by the electro-mechanical impedance (EMI) technique. Results clearly demonstrate that curved piezo transducers exhibit better performance in comparison to straight configurations for both SHM and vibration energy harvesting. A finite element (FE) analysis is also performed through a 3-D model of the real-life-sized RC beam with straight and curved piezo transducers embedded inside to evaluate the effect of various parameters such as the angle of bend, the thickness, the number of elements and the position of placement of the transducers for vibration energy harvesting. The FE simulations reveal an optimum range of the angle of bend as 130 to 160 degrees. There is a substantial impact of the increase in thickness of the transducers for vibration energy harvesting in terms of the open-circuit voltage. The numerical analysis also suggests that the optimum position of placement of the piezo transducers is towards the top or bottom of the beam cross-section. As a preliminary step towards the analytical analysis of curved piezo transducers for vibration energy harvesting, a 2-D skeletal analytical model of an RC beam embedded with a curved piezo transducer is developed by formulating a MATLAB code based on the direct stiffness approach. The effect of the curvature and the thickness of the transducer is also analysed and compared with the findings of the numerical investigations. Also, contrary to the numerical investigation results, the thickness of the curved transducer is found to hardly have any effect on the terminal voltage generated across it. This is because the 3-D effects of the structure and the strain variation across the thickness of the transducer are not considered in the analytical model where each element is considered as a 1-D element. Hence, it is recommended to extend the research to 3-D analytical models. The outcomes of the experimental and numerical investigations are very pivotal for the implementation of curved piezo transducers on real-life RC structures for improved vibration energy harvesting and structural health monitoring. This includes assessment of damages, either gradual during the lifespan of the structure or after some major event such as earthquakes. The sensor, being embedded inside the structure, is well protected from environmental degradation and can enable dynamic strain-based monitoring of the structure during normal operation or during an extreme event such as an earthquake which is technically simpler as compared to the traditional displacement-based monitoring and has special significance for monitoring of bridges under vehicular loads and for checking compliance to the Indian Roads Congress (IRC codes). Post-earthquake or during periodical SHM checks, the condition of the structure can be evaluated using the same sensor by employing the EMI technique.