复合管材内部缺陷的光声多模态导波成像理论及检测方法研究

Accurate detection of internal defects in composite pipes is an important issue which needs to be addressed by industrial and national military institutions and other agencies. It is also one of the research hot points in science and technology fields. But at present, it still remains at the stage of judging the existence, length or depth of the defects. In recent years, laser-generated guided wave tomography is a newly developed non-contact tomography method, which is the future research direction for non-destructive testing. In this proposal, the laser-generated multi-mode guided wave is studied for accurate tomography of internal defects in composite pipes. Firstly, the propagating model of the laser-generated multi-mode guided wave in composite pipes with internal defects is built up in theory, so as to study the propagating mechanism and sensitivity relationship of the interaction of laser-generated guided wave with defects, which forms the basis for efficient defects parametric inversion and image reconstruction. The recognition, separation and extraction of laser-generated multi-mode guided wave signals are researched in technique and methodology point. Efficient inversion algorithm and multi-mode guided wave tomography fusion algorithm will be developed to achieve high-resolution imaging. Finally, the theoretical analysis is verified with experiments in order to establish a more comprehensive non-destructive detection method of laser-generated guided wave tomography for composite pipes with internal defects, which is an exploratory research work for pipes detection.

复合管材内部缺陷的精准检测是工业及国防等重要机构需要解决的重大问题，也是科技界的研究热点之一，但目前对其内部缺陷的检测还停留在判定缺陷是否存在和初步判定缺陷长度和深度的阶段。光声导波成像是近年来发展起来的一种非接触式新型成像无损检测方法，也是未来无损检测的一个重要研究方向。本项目针对复合管材内部缺陷的精准成像检测，以激光激发的多模态超声导波为研究对象，首先从理论上建立含有内部缺陷的复合管材光声导波传播模型，研究光声导波与内部缺陷相互作用时的传播机理，分析光声导波与缺陷的灵敏度关系，形成有效的缺陷参数反演和图像重建的基础；然后在技术和方法上研究光声导波信号的高精度识别、分离和提取，以及发展有效的反演算法和多模态导波成像融合算法实现光声多模态导波高分辨率成像；最后从实验上验证理论分析的正确性，从而建立一套较完整的复合管材内部缺陷光声多模态导波成像无损检测方法，为管材新型探伤技术做探索性研究。

材料缺陷的精准检测是工业及国防等重要机构需要解决的重大问题。光声导波成像是近年来发展起来的一种非接触式新型成像无损检测方法，也是未来无损检测的一个重要研究方向。.本项目的主要研究内容有：.1）以含有缺陷（圆形盲孔缺陷和结构腐蚀）的材料为研究对象，通过数值模拟建立了光声导波传播模型，研究了导波与缺陷相互作用时的传播机理。 .2）针对多模态导波，研究了从混叠的多模态导波中实现模态识别和分离的方法。提出了迭代自适应多模态导波分离方法，可在无先验知识的情况下对单通道所获得的多模态导波信号实现精确分离。.3）针对在成像过程中出现的脉冲噪声干扰，研究了对脉冲噪声鲁棒的超声导波成像方法。提出了脉冲噪声鲁棒超声导波成像方法，有效解决了在实际应用中脉冲噪声导致成像出现伪影从而产生损伤虚警的问题，实现了在复杂电磁环境下的鲁棒成像。而且该成像方法布置换能器灵活，数量少，成像速度快，可广泛应用于大面积材料的超声导波无损成像检测。.4）针对在成像过程中出现的环境温度变化，研究了对环境温度变化鲁棒的超声导波成像方法。提出了环境温度变化鲁棒的超声导波成像方法，并利用弹性网络回归算法提高了成像分辨率，使得材料厚度的估计相比于传统方法更接近于实际值。.5）根据上述成像理论及方法，设计了相应的硬件平台，实现了对材料腐蚀缺陷检测的超声导波鲁棒成像系统。.上述研究内容建立了一套较完整的鲁棒超声导波缺陷成像无损检测理论和方法，为材料新型探伤技术做了探索性研究。