The Research On Early Strength And Crack Monitoring Of Concrete Based On Piezoelectric Ceramic Sensor

Structural health monitoring of intelligent piezoelectric ceramic materials is one of the hot topics in the field of engineering research.Due to its advantages of simple manufacturing process,good durability,anti-interference,high sensitivity and low cost,it has attracted much attention in the field of civil engineering structural health monitoring.At present,the reliability and safety of various concrete structures have been put forward higher requirements,so long-term testing of the structure is required.This paper is part of the research content funded by the natural science foundation of hunan province(2019JJ40313).Based on the research hotspot of structural health monitoring of piezoelectric smart materials,theoretical analysis and experimental research in the following four aspects are mainly conducted:(1)This paper briefly discusses the content and significance of the existing structural health monitoring system.With the development of science and technology,in order to meet the needs of structural health monitoring,intelligent materials have appeared.Because piezoelectric ceramic sensor has the advantages of high sensitivity,low price and fast response,as well as the dual functions of sensing and driving,this paper takes it as the main research direction.(2)In order to improve the compressive resistance and durability of the piezoelectric ceramic material and greatly reduce its sensitivity to temperature and humidity,a kind of piezoelectric ceramic sensor wrapped by cement mortar is made in this paper,which is called"intelligent aggregate".According to the strength,size,material and field distribution,the manufacture process is described.In this paper,a mechanical model of embedded thick vibration piezoelectric ceramics is established by combining "intelligent aggregate" with the main body.(3)During the curing period of concrete,this paper carried out early strength monitoring.Firstly,the physical model of early intensity monitoring based on energy fluctuation method is established to provide theoretical basis for the subsequent research.Then MATLAB tool for the intensity-signal energy curve fitting,get the relevant equation.Finally,according to the test data and the actual situation,the fitting equation between the early strength change and the signal energy is determined,so as to monitor or predict the early strength change of concrete.(4)A piezoelectric ceramic structure health monitoring system based on NI-USB-6363 portable collector was established.An embedded piezoelectric ceramic sensor was used to monitor the crack formation process of reinforced concrete specimens under concentrated load.The central frequency signal of stress wave excited by piezoelectric ceramic sensor is extracted by continuous wavelet transform and the damage index is determined according to the principle of energy fluctuation method.It is concluded that the piezoelectric ceramic sensor can well reflect the propagation law of the internal stress wave in concrete,and it can be applied to the monitoring of concrete crack damage during the service period.