Cement-based Piezoelectric Composite Shear Stress Sensor Working In D₁₅ Mode:Fabrication And Characterization

The shear strength of concrete materials of civil engineering structures is about one tenth of the compressive strength.Under the action of strong dynamic loads?such as earthquake,blasting,impact,etc.?,it is vulnerable to shear brittle failure and the structure is invalid;In anchors,the shear stress distribution and evolution with load changes are still unclear.Therefore,it is important to develop a kind of shear stress sensor,monitor the shear stress of the model and the prototype of the concrete structure,study the failure mechanism of shear stress and improve the structural reliability monitoring.The sensor based on cement-based piezoelectric composite material has good electromechanical coupling performance and piezoelectric performance.Besides,it has many advantages,such as low cost,easy processing,good linearity,good matching with concrete materials,which make it a potential material in active and passive monitoring in the civil engineering field.This paper optimize the compaction of cement piezoelectric composites based on the vacuum vibration method.In this study,the d₁₅5 mode cement-based piezoelectric material is used as the sensing element to fabricate the d₁₅ mode cement-based piezoelectric material shear stress sensor.Fathermore,this paper use shear bevel as a fixture to test the performance of shear stress sensor based on the principle of stress transformation.The specific research contents are as follows:?1?Proposed a set of vibration vacuum compacting system?vacuuming part and vibration part?and a method of vibrating vacuum.The specimens are made using three different methods including a pure vacuum,a pure vibration and mixed of vacuum and vibration.The piezoelectric,dielectric and electromechanical coupling constants and mechanical quality factors of d₃₃ mode 1-3 and 2-2 composites under different compact conditions are analyzed and compared.The test results show that the vibration vacuum method can improve the internal pores of cement-based piezoelectric composites and improve the compactness of the specimens,which improves the piezoelectricity,dielectric properties and electromechanical coupling ability of the specimens.?2?According to the shearing effect of positive piezoelectric effect of piezoelectric material,a shear stress sensor for measuring and monitoring d₁₅ mode 1-3 and mode 2-2cement-based piezoelectric composite material was proposed.This study alao analyze the measurement principle and the specific manufacturing process,including the d₁₅ mode sensing element preparing,wire soldering,waterproof sealing and sensor packing,and shielding treatment.?3?Based on the principle of stress transformation,a shearing ramp fixture was proposed.Furthermore,the shearing principle of the fixture and the stress distribution of the d15 cement-based piezoelectric shear stress sensor were analyzed.Frequency and linear characteristics of cement-based piezoelectric shear stress sensors were illustrated with the assistance of the dynamic loading system of the MTS testing machine.The results show that the shear bevel can be used to test the performance of the sensor,the d₁₅ cement-based piezoelectric shear stress sensor has a good frequency response,and the input load and output voltage have obvious linear relationship.