Research On Damage Identification Method Of Deformed Structure

The aircraft working environment is bad,the engine working condition is complex,the structure is in the high load for a long time and the different working condition environment is very easy to cause the breakdown or the damage,any minor structural damage may directly affect the flight safety of the aircraft.If the damage of the structure can be effectively identified before the accident occurs,the accident can be prevented to the maximum extent,the maintenance cost of the structure can be reduced,and the working life of the structure can be prolonged.Therefore,it is necessary to study the method of structural damage identification.With the development of new smart materials and other technologies,the deformable wing and vector engine which can change the shape are paid more and more attention.The dynamic characteristics also change with time,and the change of these parameters will bring more challenges to structural damage identification.Based on the idea that modal parameters will change after damage,the dynamic characteristics of deformed structures are time-varying.In this paper,the time-varying modal parameter identification method is HHT(Hilbert-Huang Transform),which combines empirical mode decomposition(EMD)with Hilbert transform,then an intelligent algorithm which combines EMD algorithm with three improved particle swarm optimization(PSO)algorithms is proposed.That is standard particle swarm optimization(PSO)genetic particle swarm optimization(GAPSO)and widely studied particle swarm optimization(CLPSO),which are used to identify modal parameters of time-varying systems.In addition,the damage identification and location method based on modal mode curvature difference is also studied.In this paper,a time-varying three-degree-of-freedom system with linear frequency gradient and a frequency mutation are established in MATLAB software,the modal frequency identification methods are programmed to be applied to their modal frequency identification.With reference to the vector engine structure of F-22 aircraft,the vector nozzle deformation structure experiment is designed,and the modal parameters before and after structural damage are obtained by modeling and introducing ANSYS finite element software into SOLIDWORKS software for simulation and analysis.Then,the harmonic response data obtained from ANSYS are imported into MATLAB software,modal frequencies before and after damage are obtained by using the method in this paper.The experiment of the built-in excitation vibration of loudspeaker with the vector nozzle deformation structure designed is carried out,and the experimental results of this method are verified.Through numerical simulation,finite element simulation and structural experiments,the results show that the various time-varying modal parameter identification methods proposed in this paper can better identify the damage of deformed structures.Widely studied particle swarm optimization(CLPSO)and genetic particle swarm optimization(GAPSO) are more effective.