Research On Influencing Factors Of The Performance Of Piezoelectric Smart Aggregate

In recent years,with the rapid development of smart materials and sensors,the technology of structural health monitoring(SHM)has been further developed.Piezoelectric ceramics are widely applied in SHM because of their positive and negative piezoelectric effects and combines actuating and sensing.Based on the finite element software ABAQUS,the influencing factors of the performance of piezoelectric smart aggregates(SA)are studied by numerical simulation and experimental research in this paper.In this paper,firstly the multi-physics fields piezoelectric ceramic-concrete coupling three-dimensional finite element model are established,and the C3D8R three-dimensional stress elements are used to simulate concrete,the C3D8E piezoelectric elements are used to simulate piezoelectric ceramic patches.The three-dimensional viscoelastic time-domain boundary conditions are used to reduce the reflection of the stress waves on the boundary of the finite element model.Numerical simulation shows that the stress wave produced by piezoelectric smart aggregates is composed of longitudinal wave and shear wave.Through the theoretical derivation of the output response expression of the embedded piezoelectric ceramic patches as the actuator and sensor,the influence of the size of the piezoelectric ceramic patch on the strength of the direct and inverse piezoelectric effect is studied.The theoretical results are verified by numerical simulation.Based on the established three-dimensional coupled FEM,the effect of the size of piezoelectric ceramic patches on the amplitude of stress wave is studied.According to the theoretical analysis and numerical simulation,the actuating and sensing mechanism of the embedded piezoelectric ceramic patches are obtained.The actuating process of the embedded piezoelectric ceramic patches is mainly related to the d31 vibration mode,and the sensing process is mainly related to the d33 vibration mode.The influence of the protective layer material(marble,cement mortar,epoxy resin)on the resistance and capacitance value of the piezoelectric ceramic patch in the manufacturing process of the smart aggregates as well as linear sensitivity and output signal amplitude of smart monitoring system is studied.The results show that the marble and epoxy resin protective layer have no effect on the resistance value of piezoelectric ceramic patch,but the cement mortar has a more obvious influence on the resistance value.The three kinds of protective layer materials all lead to a obvious change in the capacitance value of piezoelectric ceramic patch,and the change of capacitance of cement mortar is the biggest.The experimental results show that the output voltage signal amplitude of the smart monitoring system composed of marble piezoelectric smart aggregate is the largest,and the sensitivity of smart monitoring system is also the highest,which indicates that the efficiency of electro-mechanical transformation of piezoelectric ceramic materials is fully utilized by the marble protective layer.The influence of the inclination angle of smart aggregate on the measuring elastic modulus of concrete is studied.The experimental results show that the maximum relative error of elastic modulus measured between the condition of different angle and the condition of no inclination angle is 4.21%,which indicates that the inclination angle of smart aggregate has little influence on the accuracy of measuring concrete elastic modulus.Therefore,there is no need to consider the angle factor when the smart aggregate is fixed.Then the influence of inclination angle on the wave field direction and the wave field distribution also is studied by numerical simulation.The results show that the inclination angle has no obvious influence on the wave field distribution of longitudinal wave in different directions.