Research On Impedance Method Application In Structural Damage Monitoring

In recent decades, with the emergence of a large number of large and complex structuralengineering, Effective damage identification on the structures can provide the basic forevaluating the safety of structures. In recent years, the research on structural health monitoring(SHM) has been one of the hottest study fields. The development of smart materials providesnew approach for the long-term real-time structural health monitoring(SHM) of civilengineering. Smart piezoelectric materials such as the piezoelectric ceramic(PZT) can beemployed as both actuators and sensors and has superior characteristic including low price,quick response, broadband frequency and good linear relationship. Theoretical andexperimental study on the application of PZT for reinforced concrete structures have beencarried out.Elcectro-mechnical impedance technology is a very prospect new technique ofnondestructive examination. The technique utilizing piezoeleetric material’s direct andconverse piezoelectric effect, it’s characteristic to be used as both driver and sensor, throughdetecting and contrasting the impedance of piezoelectric ceramic sheet of before and afterdamage to realize damage diagnosis. This article through the concrete model test, forpiezoelectric impedance technology in concrete structural damage detection, mainly do thefollowing aspects:(1) Firstly, this article introduced electro-mechanical impedance technique’s uniqueadvantage(that is particularly adequate for detecting tiny damage)using instructurenondestructive examination and health monitor. It deduced the relation between structuremechanical impedance based on electromechanical coupling effect and PZT electricalimpedance.(2) This paper expounds the fundamental theory and principle of electro-mechanicalimpedance technique, introduces the piezoelectric effect, piezoelectric equation and the elasticconstitutive relation, and deduces the relationship between the mechanical impedance and thepiezoelectric admittance, as well as the selection about monitoring of sensitive frequency band,and determines the damage index. (3) In this paper, two different structure forms of concrete structures, test cube andcylinder block are formed. Through simulate the structural damage by drilling hole in theconcrete structure, measuring the changes of the PZT admittance data pasted in the concretestructure, to find the relationship between structural damage and the PZT admittance, and thenthrough comparison and analysis the result of the test, we can get the effectiveness ofmonitoring different forms of component damage based on the electro-mechanical impedancetechnique.(4)Design of concrete cantilever beam test, it analysis the relationship betweenthe location and monitoring results of PZT sensor structure, as well as the advantages anddisadvantages in the monitoring of the structural damage of the embedded and externaltype two kinds of sensors.(5) Finally, by summarize the full text, points out the defects existing in this paper and thenext step of the work, and prospects of the piezoelectric impedance method.