Research On Guided Wave Damage Monitoring Of Structures Under Time-Varying Conditions

In local structural damage detection,the guided wave signal because of its sensitivity to the structure change has been widely used in research,but in actual engineering,the change of time-varying conditions will affect the guided wave signal,such as frequency offset and the size of the amplitude change,which may lead to false alarms,reduce the reliability of the damage monitoring.Therefore,it is of great significance to study guided wave damage monitoring under time-varying conditions.In this paper,mechanical and electrical impedance technology is used to conduct damage discriminant analysis on structures under different temperature conditions,and the characteristic parameters of signals are extracted as the basis to judge the state of the structure.The temperature compensation based electromechanical impedance damage monitoring and automatic classification method can effectively reduce the influence of temperature environment change on damage monitoring.The research contents and experiments of this paper are as follows:(1)Several commonly used structural health monitoring methods are described,and the research on the influence of time-varying conditions on damage monitoring signals and their optimization schemes are introduced.The piezoelectric effect is analyzed and the theory of electrical impedance technology is studied.(2)This paper introduces several commonly used impedance measurement methods,analyzes their advantages and disadvantages,and selects suitable voltage and current method to collect impedance signal and admittance signal of the structure to be measured according to the experimental requirements.On this basis,the admittance signal is decomposed into real part signal and imaginary part signal according to the formula.Several commonly used signal characteristic parameters are introduced.(3)The effects of temperature environment change and damage on response signal and signal characteristic parameters are analyzed,and then the damage monitoring under the coupling condition of temperature change and damage is further analyzed.In order to effectively reduce the influence of temperature change on damage monitoring,a method of electromechanical impedance damage monitoring and automatic classification based on temperature compensation is proposed based on the idea of pattern recognition.(4)By combining the construction of the data processing software and hardware system,in the last,an experiment is conducted on composite material plate with within a wide range of temperature to collect baseline data set,in the condition of unknown test data,using the imaginary part of the test data signals matching the imaginary part of the baseline data and further to extract the corresponding real component signals,The cross-correlation function is used as a new damage characteristic parameter to monitor the damage,and the state of the structure in the test data can be well classified.The experimental results verify the feasibility and effectiveness of the proposed method for damage monitoring on composite panels under the condition of temperature variation,which can effectively reduce the false alarm caused by environmental temperature variation,and provide a new idea for solving the influence of time-varying conditions on structural health monitoring.