Influences Of Environmental Humidity On The Piezoelectric Admittance Signal

With the rapid development of social economy,the progress of science and technology,there are many large construction projects emerged,which are beneficial to the people's livelihood,safety and reliability during the past decade.The traditional nondestructive testing methods have been abandoned in recent years for its drawbacks and limitations,and in recent years the structural health monitoring system of piezoelectric impedance technology has become a main research field because of its convenience,reliability,flexibility and real-time monitoring and other advantages.A large number of studies show that the influence of temperature and the external force will affect the effect of EMI damage detection technology,however,the studies on EMI detection technology of piezoelectric admittance test signal the influence of humidity changes is few,in order to further improve the application of EMI technique in practical engineering,this thesis focuses on the influence of humidity change on the piezoelectric admittance test signal and makes research on the following aspects:1.This thesis makes the theoretical analysis on the change of environmental humidity to the influence of piezoelectric ceramics.Piezoelectric ceramic is based on piezoelectric impedance technology,as a kind of ceramic material,the internal porosity is an important factor affecting the elastic modulus.With decreasing porosity,its elastic modulus will increase sharply with time.With the increase of the environmental humidity,the piezoelectric ceramic pores of adsorbed water molecules will emerge.Increasing water molecules will lead to reduced pressure piece internal porosity of electricity,resulting in the increase of the elastic modulus of ceramic materials and the natural frequency of the piezoelectric ceramic piece increases.2.This thesis carried out the environmental study on the impact of the humidity change on the piezoelectric ceramic.By measuring and analyzing the change of the conductivity of the piezoelectric ceramic,it is found that the peak value of the piezoelectric admittance signal of the piezoelectric ceramic is gradually increased with the increase of the humidity,which indicates that the humidity change natural frequency of Piezoelectric Ceramic.3.This thesis carried out the environmental study on the impact of the humidity changes on the piezoelectric admittance test signal.By comparing the changes of the piezoelectric admittance signals fed by the piezoelectric ceramic on the concrete test block,the frequency values corresponding to the peak values of the piezoelectric admittance curves of the piezoelectric ceramic sheets were extracted by the three groups with the change of humidity,which means that the piezoelectric admittance test signal has been affected.