Research On Load Influence Compensation Method For Piezoelectric-guided Wave Structure Health Monitoring

Piezoelectric guided wave-based Structural Health Monitoring(SHM)technology can realize the monitoring of small damage and large area of the structure,and it has gradually become a research hotspot.However,real aerospace structures operate in time-varying environment,thus boundary conditions and other factors as the load will affect the reliability of monitoring.Aiming this problem,this paper studies the influence of the load on guided waves with both theoretical and experimental methods.And the compensation method is also studied to eliminate the influence of the load.The main innovations and efforts are as follows,(1)The influence mechanism of load on guided waves is studied,and guided waves propagation experiments on metal and composite structures under load are carried out.The amplitude and phase of guided wave signals is quantified under changing load conditions.And the least square method is also used to fit the experimental data.The results shows the amplitude and phase of the guided wave signals changes linearly with the load.(2)Based on the influence of the load on the guided wave signals,a load compensation method based on an Adaptive Linear Neuron(ADALINE)network is proposed.It realizes the load compensation of the signals under the load range of 0 ～ 100 MPa with the load interval of 20 MPa.The compensation accuracy is higher than-25 d B,and only a small amount of reference guided wave signals and network weights need to be stored.(3)Aiming at the influence of the load on the piezoelectric-guided wave SHM technology,the load compensation method based on the ADALINE network and the delay accumulation imaging method is combined.By carrying out the damage monitoring experiment under the influence of the load on the plate structure,the structural damage diagnosis under the influence of the load is realized.For experimental date failing to realize locating and imaging,load compensation method is applied.Then loacting and imaging is successfully performed with high accuracy.The results shows this method significantly improves the reliability of SHM techonology based guided waves.