| Blade is the key component of wind power generation system.The rapid development of wind power generation technology puts forward more and more stern requirements for blade materials.CFRP which has the advantages of low density,high specific strength / specific modulus and good fatigue resistance,is regarded as ideal material for high-performance blades.However,the microstructure of CFRP is a complex multiphase system,which is prone to structural defects such as porosity and delamination in the process of material preparation,processing and use.These defects will obviously reduce the bearing capacity and service span of the material.Therefore,in order to improve the service life of wind turbine blades and avoid major significant disasters and accidents,rapid and efficient nondestructive testing must be implemented on the surface and interior of wind turbine blades.Ultrasonic guided wave has the advantages of long propagation distance,low attenuation and sensitivity to defects.Based on the basic theory of ultrasonic Lamb wave and with the help of ABAQUS finite element software,this paper simulates the interaction process between ultrasonic Lamb wave and several common defects in CFRP,and uses the reflected echo characteristics of Lamb wave and defects to realize the nondestructive testing of CFRP materials.The main research contents include:1.Propagation law of Lamb wave in solid.Based on the study of the basic theory and dispersion characteristics of Lamb wave,the dispersion equation of Lamb wave propagation in CFRP is deduced and numerically solved,and the dispersion curve is drawn,so as to determine the selection of Lamb wave excitation signal mode.2.Propagation characteristics of Lamb wave in CFRP of different defect characteristics.With the help of ABAQUS finite element software,the interaction process between Lamb wave and surface and internal groove defects,internal crack defects and layered defects is simulated,and the time domain and amplitude characteristics of reflected echo caused by the depth,width,radius and center position of defects are obtained.The results show that the specific situation of defect distribution can be judged by combining the stress displacement amplitude of defect echo and the time-domain characteristics of echo signal.3.Delamination defect location algorithm.In the form of multi-sensor array,the basic theories of rapid imaging algorithm,trajectory location algorithm and Bayesian location algorithm are studied,and the damage imaging images under the abscissa and ordinate coordinates of different damage centers are drawn.The results show that Bayesian location algorithm combines the advantages of rapid algorithm and trajectory location algorithm,and the location error is the lowest. |
