CFRP层压板超声导波相控阵成像检测方法研究

Guided wave phased array inspection methods based on classical focusing laws may fail due to the anisotropic and inhomogeneous behavior of CFRP laminates. Therefore, it is urgent to develop an efficient and reliable theoretical modeling method to accurately predict the dispersion effect and skew effect of the guided waves in CFRP laminates, in order to develop guided wave phased array inspection method for composite materials. However, when the traditional matrix methods are used to solve the guided waves in anisotropic multilayer structures, the problems such as numerical instability, the poor convergence, and tracing wrong modes may occur. This project intends to integrate and improve the Legendre polynomial method and state vector method, in order to propose a new method based on the characteristic spectrum for solving the dispersion characteristics. The analytical model of the guided wave skew effect is established. The influence mechanism of the anisotropic parameters of laminates on dispersion characteristics and skew effects is analyzed. A new method of guided beam steering/focusing is proposed to characterize the guided wave focusing performance for various array configurations. The wavefield imaging techniques such as filter reconstruction imaging and spatial wavenumber imaging are developed.By extracting the local space-wavenumber spectrum of the guided wave phased array field information, the distribution and variation of the wavenumber components in space are excavated. The combination of the phased array imaging and wavefield imaging will be used to achieve a hierarchical evaluation of defect size, depth and shape. Finally, this project will provide technical support and solutions for non-destructive evaluation of composite materials.

CFRP层板具有显著的各向异性和非均匀性特征，基于经典聚焦法则的导波相控阵检测方法很有可能会失效。因此，迫切需要发展一种高效可靠的理论建模方法，精确预测CFRP层板的频散效应和偏斜效应，以开发适用于复合材料的导波相控阵检测方法。但传统矩阵方法在求解各向异性多层结构导波时，会出现数值不稳定、收敛困难，模态追踪错误等问题。本项目拟通过融合并改进勒让德级数展开法与状态矢量矩阵法，提出一种基于特征谱的频散特性求解新方法，建立导波偏斜效应的解析模型；分析各向异性参数对频散特性和偏斜效应的影响机制，提出导波波束偏转/聚焦的调控新方法，表征各种阵列配置的导波聚焦性能；发展滤波器重建成像和空间波数成像等波场成像技术，通过萃取导波相控阵波场信息的局部空间-波数谱，挖掘波数分量在空间上的分布与变化；融合相控阵成像分析和波场成像分析，精确地表征缺陷的位置、形状与大小，为复合材料的无损评价提供技术支持和解决方案。

项目立足于CFRP复合材料的无损表征和结构健康监测，在CFRP层压结构导波传播特性、CFRP层板超声导波波束偏转/聚焦、CFRP层压板典型缺陷检测与定位、CFRP层压板缺陷边缘信息表征等方面取得了重要进展，完成了项目预定目标。研究内容主要包括：（1）融合状态矢量法与勒让德多项式展开法，系统地构建了CFRP层板/管结构超声导波传播的解析模型，揭示了完全各向异性弹性方程中所隐藏的结构特性，给出了一般各向异性层板/管超声导波的求解方案，突破了传统矩阵法无法求解各向异性圆柱结构频散特性的难题，揭示了材料参数和层状结构参数对导波传播特性的影响规律，确立了适用于相控阵检测的导波模态优化选择规律；（2）建立了复合材料层压板导波能量偏斜角的解析模型，分析了各种阵列配置参数对CFRP层板导波聚焦波束的影响规律，创建了补偿相位延迟和空间相移的波束偏转/聚焦调控新路径，提出了一种考虑导波能量偏斜效应的相控阵检测新方法；（3）分别开展了基于波束偏转/聚焦的超声导波相控阵全角度扫查缺陷检测、基于时域/频域调控的超声导波相控阵缺陷检测和基于频率-波数分析的CFRP层压板缺陷边缘信息表征等成像技术方面工作的研究。利用上述技术实现了对CFRP层压板中的缺陷与损伤的可视化成像检测，为CFRP复合材料的无损检测与评价提供技术支撑和解决方案。