Research On Damage Imaging Technique For Plate-Type Structures By Using TR-MUSIC Algorithm

Because the Lamb wave-based damage imaging technique for plate-type strutures can supply direct-viewing information of the location and size of the damage,it has been one of the research focuses in the field of aeronautical structural health monitoring.This technique uses Lamb wave as the transmission medium of damage information,and combines advanced imaging algorithm to achieve the on-line monitoring of the structural damage and its expansion,which is significant to ensure the aircraft structural integrity,improve the safety of flight and reduce the cost of maintenance.Although the location of structural damage has been realized by the existing Lamb wave-based damage imaging technique,due to the diffracting limitation of Lamb wave,the image resolution is limited by the Rayleigh criterion,that is,when the distance between the two structural damage is less than a certain threshold(similar to the wavelength of Lamb wave,and the wavelength of the frequency band range used in the existing Lamb wave-based damage imaging technique is between 10 mm and 20 mm),the image methods can not distinguish the two objectives,which limits the further development of structural health monitoring based on Lamb wave.Therefore,improving of the resolution of Lamb wave-based damage imaging technique is of importance and practical significance to the forward development of structural health monitoring technology.This paper adopts a method combing finite edement simulation and experimental verification to research structural health monitoring technique based on Lamb wave and TR-MUSIC algorithm systematically.The main content includes:(a)Based on linear piezoelectric sensor array,the ability of TR-MUSIC algorithm to identify single and multiple damages and the super-resolution imaging capability of half-wavelength spacing damages in structures are studied.And the relationship between the eigenvalues of time reversal operator and damages is explored,a monitoring strategy based on eigenvalue function is proposed to solve the problem that the damage identification ability of TR-MUSIC is affected by boundary scattering signals.(b)Based on two-dimensional piezoelectric array,the virtual image problem in TR-MUSIC damage identification technique based on linear piezoelectric array is solved,and the omnidirectional health monitoring of plate srtructure is realized.On this basis,the TR-MUSIC algorithm is applied to the precise location of single and multiple damages in the aeronautical aluminum plate structure by measuring the structural Green's function.(c)Based on the ring piezoelectric array,the shape recognition ability of TR-MUSIC algorithm for structural damage is studied.The shape recognition of rectangular and umbrella damage is realized.A partition method based on eigenvalue energy function is proposed to solve the problem that the signal subspace and noise subspace boundaries are not obvious in the damage shape recognition of TR-MUSIC algorithm.