Damage Identification And Monitoring Of Concrete Based On PZT

Concrete is the most widely used civil engineering material at present,and its safety and reliability have a significant impact on the development of society.However,in view of its multi-scale mixing and process of hydration and gelation,concrete inevitably has damage like internal defects and even cracks leading to the surface.Under the action of external environment and its own load,concrete damage will continue to accumulate during its service period.When the damage accumulates to a certain extent,the safety and durability of the structure will be reduced,which may cause extremely serious consequences under extreme conditions.How to realize the damage identification and monitoring of concrete has been a hot research topic in civil engineering,and put forward many structural non-destructive testing technology.However,the concealment of concrete damage and technical limitations of nondestructive testing means,make the traditional detection methods can’t achieve long-term real-time health monitoring of concrete structures.In recent years,piezoelectric intelligent materials,represented by piezoelectric ceramics,have become a research hotspot in the health monitoring of concrete structures due to their advantages of driving and sensing as a whole,low price and sensitive response.A series of theoretical and experimental studies on the health monitoring of concrete structures have been carried out based on piezoelectric ceramics.Focusing on the identification and monitoring of concrete damage,this paper proposes a concrete damage identification and monitoring method based on piezoelectric ceramics.The main work contents are as follows:(1)Plastic balls of different sizes were placed in the concrete specimen to simulate the damage inside the concrete,and piezoelectric ceramic elements were placed inside the concrete specimen as drivers or sensors to send and receive signals.The wave propagation analysis method based on piezoelectric ceramics was used for damage identification and monitoring.According to the principle that the stress wave will attenuate when passing through the non-uniform area of medium,the internal health condition of concrete is judged by analyzing the characteristic parameters such as time domain amplitude and frequency domain amplitude of the signal received by the sensor,and the damage index is put forward to measure the damage degree based on the signal amplitude.The results show that the internal damage of concrete will lead to the variation of the time domain amplitude and frequency domain amplitude of the received signal,and the damage index proposed in this paper can be used to evaluate the damage degree well.The effectiveness of the wave propagation analysis method based on piezoelectric ceramics in the identification and monitoring of concrete internal damage is verified.(2)Using wave propagation analysis method based on piezoelectric ceramics to monitor concrete crack damage and damage development trend.The crack of different depth is cut on the concrete specimen,and the signal is sent and received every time the crack is deepened.According to the stress wave after fracture happens when the refraction and reflection phenomenon leads to stress wave attenuation after through the cracks,through time domain signal analysis and wavelet packet energy when there is a different depth of cracks on concrete sensor signals are compared,and puts forward the corresponding damage based on wavelet packet energy index to judge the damage degree and monitoring cracks development trend.The results show that the existence of cracks causes the variation of the received signal’s time-domain amplitude and the wavelet packet energy,and the damage index based on the wavelet packet energy is very sensitive to the damage identification,and can accurately describe the development trend of the damage.It is proved that the wave propagation analysis method based on piezoelectric ceramics is effective in the identification and monitoring of concrete crack damage.