Study On The Electromechanical Properties Of PZT-based Piezoelectric Ceramics And Its Application In Dynamic Stress Detection Of Concrete

Concrete structure can be seen everywhere in people's production and life.It is not only subjected to static load,but also inevitably subjected to various dynamic loads during its life.Nowadays,the research on the mechanical properties of concrete structures under dynamic loads has become one of the hotspots in the field of civil engineering.At the same time,the implementation of health monitoring and prediction relying on intelligent monitoring system has become a trend.Piezoelectric ceramics with driving and sensing capabilities are widely used because of their fast response,wide frequency response range,good linear relationship,easy tailoring and low cost.Under such conditions,the piezoelectric ceramics are embedded in reinforced concrete structures,and the monitoring and detection of their internal dynamic stress has aroused a research upsurge in the field of Engineering structures.However,the existing piezoelectric ceramics on the market can not meet the wide application requirements,so it is particularly important to develop a piezoelectric ceramics with excellent performance to make stable and reliable sensors.In this paper,PZT-based piezoelectric ceramics were prepared by traditional solid-state method.The properties of PZT-based piezoelectric ceramics were improved by doping and adjusting sintering temperature.Finally,Nb/Ce co-doped Pb?Zr0.52Ti0.48?O 3 piezoelectric ceramics?PZT-NC?were prepared by sintering at different temperatures between 1150 and1250.Then the electrical performance of the sensor is studied,and a piezoelectric ceramic sensor with excellent performance is developed and calibrated.The specific work is as follows:Firstly,the electrical properties of the PZT-NC piezoelectric ceramics were tested:the relative density was measured by Archimedes method,the crystal structure of the ceramics was analyzed by XRD technology,and the microstructure and chemical composition of the ceramics were analyzed by SEM technology.Curie temperature,dielectric constant and dielectric loss were measured by dielectric temperature method,and piezoelectric constant was measured by quasi-static method.The results show that with the increase of sintering temperature,the peak dielectric constant strength increases,Curie temperature Tc and relative dielectric constant e r decrease,dielectric loss tan delta increases first and then decreases,and piezoelectric coefficient D 33 increases continuously.The improvement of piezoelectric properties can be attributed to the domain wall pinning effect in coarse grains.Through the study of electrical properties,it can be seen that the PZT-NC piezoelectric ceramics sintered at 1225?have the best electrical properties.Secondly,the mechanical properties of PZT-NC piezoelectric ceramics sintered at 1225?were tested:the fracture toughness was tested by indentation method,the bending strength was tested by three-point bending method,the resistance curve?R curve?was analyzed by indentation strength bending beam method,and the bending strength and dispersion were analyzed by Weibull statistical method.The test results show that the fracture toughness of PZT-NC piezoelectric ceramics exhibits obvious anisotropy due to ferroelastic toughening.In air,water and silicon oil,the fracture toughness of PZT-NC piezoelectric ceramics increases in turn.At the same time,the fracture toughness of PZT-NC piezoelectric ceramics decreases gradually with the increase of ambient temperature due to ferroelastic toughening.As crack propagates,the gravitational field at crack tip induces a 90-degree turning of ferroelastic domain and increases the resistance of crack propagation,resulting in a higher fracture toughness plateau value(K_IRmax)parallel to the polarization direction and a maximum value of K_max up to 0.632MPa m^1/2 in parallel to the polarization direction,as the ferroelastic toughening hinders the crack propagation in bending fracture and improves the parallel to the pole.The flexural strength and reliability are improved.Through further analysis of its mechanical properties,we can see that it not only has good mechanical properties in air,but also has better fracture toughness in water and oil.At the same time,it can adapt to high temperature environment,which lays a foundation for its reliable application in concrete structures with harsh environment.Finally,on the basis of the work done by predecessors,the fabrication process of the embedded piezoelectric ceramic stress sensor for concrete structure is improved.The PZT-based piezoelectric ceramic is embedded in the concrete cube,and the sensitivity of the piezoelectric ceramic stress sensor under sinusoidal dynamic load is calibrated by servo actuator.The improved sensor has more uniform force,better waterproof and insulation performance,better dynamic load response and more stable performance.Whether the loading frequency is high or low,whether the load intensity is high or low,there is an obvious linear relationship between the output charge value and the input stress value of the sensor,and the output waveform and the input load are synchronized in time.The sensor has high sensitivity and accuracy.Therefore,the embedded piezoelectric ceramic stress sensor studied and fabricated in this paper has reliable performance and can be widely used to monitor the dynamic stress in concrete structures.