Research On The Intelligent Piezoelectric Layer Sensor Technology Based Structural Health Monitoring

Piezoelectric sensors and Lamb wave based structural damage diagnostic method is sensitive tosmall damage in composite structure and can be used to monitor the composite structure. With theintensions to enhance the reliabilities of SHM system, this thesis focused on subjects of the design ofpiezoelectric-layer(PZT layer) and the research of temperature effect on signals, which were asfollowed:According to the analysis of the active Lamb wave structural health monitoring signal equationbased on the piezoelectric sensors, figure out that, signals are effected by the following factors:piezoelectric coefficient, dielectric constant, young’s modulus; adhesive fillet thickness,shear modulus; young’s modulus and density of the structure when temperature changes.To the key technical issue of piezoelectric sensors reliability and encapsulation of piezoelectricsensor based structural PHM system integration, the existing design methods of piezoelectric smartlayer are studied in section two. Based on this research, a reliability design method of piezoelectricsmart layer based on hybrid technology of welding and bonding, rigid-flexible combination and linespacing against the electromagnetic interference is proposed and researched. Based on this method,the piezoelectric smart layer is developed. Through the durability test of temperature and fatigue, thedeveloped piezoelectric smart layer is proved to be well suited for engineering environment.The thesis analyzes the temperature effection on the active Lamb wave propagation. Throughexperiment, the thesis discusses the relationship between the time delay of wave packets with theamount of the temperature variation, and the different temperature effections on the A0、S0mode.The temperature compensation is conducted by the combination of ADALINE adaptive filter andthe selection of baseline signal. With the method above, a precise temperature compensation from-40℃to80℃is achieved with an error lower than-25dB for composite material. For themodulated sine signal with central frequency of50kHz and450kHz, which on behave of A0mode andS0mode, the baseline signal is selected every20℃and12℃, respectively.