Study On Damage Detection And Health Monitoring Of Wooden Structure Based On Piezoceramic Transducer Enabled Active Sensing

In recent years,piezoelectric-based sensors and techniques have made significant advances in structural health monitoring and damage assessment of various metal and concrete structures.With the deepening of research,active monitoring technology based on piezoelectric ceramic sensors has been widely used in structural damage detection and health monitoring in civil engineering.Timber is a resource-rich and renewable material that is widely used as a building material in many countries.However,piezoelectric-based sensors and methods lack research on damage detection and health monitoring of timber and wooden structure.Based on the active monitoring technology of piezoelectric ceramic sensors,the damage detection and health monitoring of timber and wooden structures are studied in this paper.The main research contents are as follows:(1)Based on the active monitoring method of piezoelectric ceramic,the feasibility of non-destructive real-time and quantitative monitoring of moisture content in timber was studied.Moisture content monitoring was carried out by placing a pair of lead zirconate titanate(PZT)patches on the surface of timber.The piezoelectric ceramic patch acts as a driver to generate the designed directional stress wave signal,while the other piezoelectric ceramic patch acts as a sensor to receive the transmited stress wave signal.The moisture content of timber specimens gradually increased from 0% to 60%,and the increment was 10%.The material properties of timber vary correspondingly with different moisture content,which results in measurable differences in energy attenuation rates of stress waves of different specimens.The results show that there is a parabolic relationship between the energy signals received and moisture content by timber specimens.The feasibility and reliability of the method for monitoring moisture content of timber are discussed.(2)Based on the active monitoring method of piezoelectric ceramic,the feasibility study of timber damage detection on the surface of wooden structure is carried out,and the typical damage modes such as surface cracks and holes in wooden structure are studied.In the active monitoring method,a piezoelectric ceramic sensor acts as a driver to generate stress waves propagating along the surface of the wooden structure,while other piezoelectric ceramic sensors are act as receivers to detect the transmitted stress waves.Defects such as cracks or holes cause the attenuation of stress wave propagation.This method is used to detect the structural defects based on wavelet packet damage index(RMSD),which verifies the feasibility of real-time damage detection for timber.(3)The mechanical-electrical multi-physical field coupling model of piezoelectric ceramics and timber was established by finite element analysis software ABAQUS.The numerical simulation of the excitation and reception stress waves of PZT patches mounted on the surface of wooden structure beams,and studies the stress wave in the medium.The propagation process of stress waves in the medium and the mechanism of wooden structure damage identification based on active monitoring method of piezoelectric ceramics were studied,in which the multi-anisotropy of wooden structure was considered.The effects of damage modes are considered by the combination of implicit analysis and explicit analysis for the contact relationship between piezoelectric ceramics and wooden structures.(4)Comparing the calculated results of the finite element multi-physical field coupling model of piezoelectric ceramics and wooden structures under different damage states with the results of wooden structure damage monitoring tests,the experimental data verify the accuracy of the finite element model,and verify the accuracy.The validity and reliability of the established finite element model for the simulation of wooden structure health monitoring and damage assessment based on piezoelectric ceramics.In summary,it is feasible to apply the active monitoring technology based on piezoelectric ceramic to the damage detection and health monitoring of wooden structures.Based on this method,the health status and damage degree of the timber and wooden structures can be effectively monitored.