复合材料表面缺陷的超声扩散场定位

传统超声检测多使用直达波进行检测,但在各向异性、非均匀的复杂结构检测中存在诸多限制。将超声波在此类多重散射介质中的传播近似为扩散过程,探索采用超声扩散场信号进行复合材料表面缺陷的检测定位。在此过程中形成的扩散场能对介质密集采样,对缺陷的出现高度敏感。针对铺层结构为0°/90°]₁₂的碳纤维增强环氧树脂基复合材料板,基于Locadiff方法建立表面缺陷定位的理论模型,开展缺陷出现前后波形的理论不相关性计算。结合实验求解扩散系数,开展检测信号的不相关性分析。最后利用反演计算的模型给出缺陷的定位结果。结果表明,当缺陷直径为10 mm时,定位误差为6.99%;当缺陷直径为5 mm时,定位误差为9.29%,可以实现复合材料表面缺陷的定位。 

Surface defect localization in composites with ultrasonic diffuse field

The direct wave part is often applied in traditional ultrasonic detection method.However,limitations are encountered during the inspection of anisotropic and non-homogeneous structures.In this work,the ultrasonic wave propagation in such multiple scattering media is treated as a diffusion process.The surface defect localization with the ultrasonic diffuse field is explored.The diffuse wave field is sensitive to the defect through dense sampling of the medium.Regarding to the carbon fiber reinforced epoxy plate with 0°/90°]₁₂ layer-up,a theoretical model is established based on the Locadiff method,from which the decorrelation analysis is realized with the defect sensitivity kernel.According to the measured waveforms before and after the defect appearance,both the diffusivity and decorrelation coefficients can be determined.The defect location can be achieved with an inversion algorithm finally.The results show that the minimum localization error is 6.99% for the defect of 10 mm in diameter while 9.29% for the defect of 5 mm in diameter.The diffuse wave is promising for the defect inspection in composites.