Application Of Electromechanical Impedance And Ultrasonic Guided Waves Technologies In Defects Detection And Location Of Composite Materials

Structural health monitoring technology based on electro-mechanical impedance technology(EMI)has the advantages of high local sensitivity,no model analysis,and so on.It has unique advantages in the field of on-line monitoring of new material structures,such as composite structures for aircraft and spacecraft.Because of its high sensitivity,the electro-mechanical impedance technology is easy to be affected by the detection of environmental factors.In this dissertation,the influence of temperature on the structural health monitoring technology based on electro-mechanical impedance technology was studied.The experiments were carried out in aluminum beam and composite beam,and the effect of temperature on the electro-mechanical impedance technique was eliminated by combining the data fusion algorithm.Ultrasonic guided waves monitoring technology has the advantages of high detection efficiency,wide detection range and fast detection speed.It is particularly suitable for health monitoring of plate-like structures.In this dissertation,the characteristics of the local high sensitivity of electromechanical impedance technology combined with the characteristics of the wide detection range of ultrasonic guided waves technology.A new data fusion algorithm was developed for health monitoring of composite plate,and the identification of damage was achieved.The main research contents are as follows:(1)The design of temperature compensation algorithm based on electromechanical impedance technology.In order to eliminate the influence of temperature in structural health monitoring based on electro-mechanical impedance technology,the experimental aluminum beam and the composite beam were experimentally studied,and an effective quantitative temperature compensation algorithm is proposed.This compensation algorithm can compensate the temperature-dependent impedance signals by using the law of the reference signal with temperature.And the temperature compensation algorithm is applied to the damaged structure.(2)Electro-mechanical impedance technology and ultrasonic guided waves technology were used to study the damage location of composite plate.Based on the ultrasonic guided waves technology,the damage detection experiment used two kinds of excitation methods to collect the signals.These two kinds of excitation modes were the pulse-echo mode and the pitch-catch mode,and the pitch-catch mode was used to realize the damage location inside the sensor array,and the pulse-echo mode was used to realize the damage localization of the outer area of the sensor array.(3)Based on electro-mechanical impedance and ultrasonic guided waves synthesis technologies,a new imaging algorithm was designed to image the detection results of these two monitoring techniques respectively.And a new data fusion algorithm was proposed.This algorithm can improve the positioning accuracy of the defect by calculating the comprehensive damage index,and realize the location and imaging of the defect in the whole composite material plate.