Research On Sensing Technology Based On Resonance Frequency Of Piezoelectric Element

Local structural health monitoring techniques based on piezoelectric ceramic materials(e.g.,Electromechanical impedance(EMI)method and acoustic emission technique,etc.)have been successfully applied in the field of civil engineering.When piezoelectric ceramic sensors are used for structural health monitoring in civil engineering structures,different occasions have different resonant frequency requirements.However,there are still many problems to be further studied on how to design sensors based on the characteristics of the resonance frequency of piezoelectric elements to meet the monitoring requirements.In order to solve this problem,the resonance frequency characteristics of the radial vibration of the piezoelectric element were studied in depth.Combining with the characteristics of the traditional local structural health monitoring technique based on piezoelectric ceramic materials,the piezoelectric transducers suitable for the health monitoring of large concrete structures are proposed.The following are the main contents of this paper:(1)The resonance frequency characteristics of the piezoelectric element are studied in depth.In this paper,an equivalent circuit model of a series piezoelectric element is established based on the resonant frequency derivation process of the piezoelectric element.The resonant frequency characteristics of piezoelectric elements before and after series are studied by equivalent circuit model and finite element simulation.Finally,the resonance frequency characteristics of the piezoelectric element before and after series are further studied by experiments.(2)Based on resonance frequency characteristics of series piezoelectric element,a series piezoelectric element impedance transducer was designed.Based on the resonance frequency characteristics of series piezoelectric element and the basic principle of impedance method,a multi-sensing EMI method based on series piezoelectric element is proposed.The feasibility of monitoring grouting compactness with multi-sensing EMI method is verified by experiments,and the basic principle of the method is further studied by finite element simulation.(3)An embedded acoustic emission sensor was designed based on the resonance frequency characteristics of the radial vibration of a piezoelectric element.Considering the characteristics of acoustic emission signals released by concrete cracks,the designed sensor is suitable for acoustic emission monitoring embedded in mass concrete structures.The performance of the designed embedded acoustic emission sensor is tested by concrete uniaxial compression experiment.