Study On Hole Crack Damage Guide Wave Detection Of CFRP Plate Based On Magnetostrictive Transducer

CFRP materials are gradually replacing steel in the aerospace and automotive sectors due to their high specific gravity and strength.In service the material is assembled in the form of a shell riveted or bolted to the substrate to ensure that the material is firmly connected to the substrate.However,the substrate is often subjected to high air pressure and unpredictable impacts in the service environment,resulting in unqualified loads on the connection holes.Due to the brittleness of this material,continuous loading will cause the edge of the joint hole to break and delaminate,if this is not detected and the material replaced in time then an accident will occur where the material is disconnected from the substrate.This is essential for the detection of cracks in CFRP plate holes.This paper proposes an ultrasonic guided wave detection method for hole cracks,taking advantage of the wide propagation range of guided waves and their sensitivity to defects.The design of a miniature magnetostrictive transducer for high frequency ultrasound guided wave damage detection,and is also a preliminary attempt to address the high attenuation coefficient of CFRP materials.Firstly,the mechanical properties of CFRP materials are analysed in depth,and the relationship between strain and propagation angle of orthotropic anisotropic CFRP materials is investigated.Combined with the mechanical properties,the dispersion equation of the material is derived,and the dispersion curves of CFRP plates in each direction are calculated with modelling simulations as a theoretical basis for the crack detection method.The material properties of Galfenol are detailed,and the magnetising strain properties of the material and the strain output are analysed.A cylindrical magnetostrictive transducer has been designed based on the magnetic field driving properties of the material and the detection environment.A mechanical model of the magnetic field distribution of the transducer and the operating strain output was investigated,a simulation model of the transducer was constructed,and the modal species and driving magnetic field distribution of the transducer during the detection process were calculated.The noise factors generated during ultrasonic inspection of CFRP plate damage were studied,and the noise generation mechanism was analysed.Using the sensitivity of ultrasonic guided wave modes to damage,the method is proposed to reduce noise to significant damage modes to achieve accurate damage detection.The method is based on the original wavelet decomposition with STFT clouds,and proposes a method to modulate the cloud colour gamut values according to the noise amplitude characteristics to achieve noise reduction.Finally,to verify the validity of the detection method,the Galfenol transducer was used as the high-energy excitation source for the ultrasonic guided wave,and the PZT-5 was used as the receiving end for the ultrasonic guided wave detection experiment for crack detection.The optimal excitation frequency of the transducer was investigated.Comparison of the signals with and without crack damage revealed that the damage modes were evident,and the extraction of damage amplitudes enabled quantification of damage.