Inverse analysis is a promising tool for quantitative evaluation offering informative model-based prediction and providing accurate reconstruction results without preinspections for characterization criteria. For the traditional defect inverse reconstruction, a large number of parameters are required to reconstruct a complex defect, and the corresponding forward modeling simulation is very time-consuming. Such issues result in ill-posed and complex inverse reconstruction results, which further reduce its practical applicability. In this article, we propose and experimentally validate an inversion technique for the reconstruction of complexly shaped delamination defects in a multilayered metallic structure using signals derived from infrared thermography (IRT) testing. First, we employ a novel defect parameterization strategy based on Fourier series fitting to represent the profile of a complicated delamination defect with relatively few coefficients. Second, the multimedium element modeling method is applied to enhance a finite element method (FEM) fast forward simulator, in order to solve the mismatching mesh issue for mesh updating during inversion. Third, a deterministic inverse algorithm based on a penalty conjugate gradient algorithm is employed to realize a robust and efficient inverse analysis. By reconstructing delamination profiles with both numerically simulated IRT signals and those obtained through laser IRT experiments, the validity, efficiency, and robustness of the proposed inversion method are demonstrated for delamination defects in a double-layered plate. Based on this strategy, not only is the feasibility of the proposed method in IRT nondestructive testing is validated, but the practical applicability of inversion reconstruction analysis is significantly improved.

中文翻译：

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多层结构分层缺陷定量红外热成像评价反演技术


逆分析是一种很有前景的定量评估工具，可提供基于模型的信息丰富的预测，并提供准确的重建结果，而无需预先检查表征标准。传统的缺陷逆重建需要大量的参数来重建复杂的缺陷，并且相应的正向建模仿真非常耗时。这些问题导致逆重构结果不适定且复杂，进一步降低了其实际适用性。在本文中，我们提出并通过实验验证了一种反演技术，该技术可利用红外热成像 (IRT) 测试产生的信号来重建多层金属结构中形状复杂的分层缺陷。首先，我们采用基于傅里叶级数拟合的新型缺陷参数化策略来表示具有相对较少系数的复杂分层缺陷的轮廓。其次，应用多媒体元建模方法增强有限元法（FEM）快速正演模拟器，以解决反演过程中网格更新的不匹配问题。第三，采用基于罚共轭梯度算法的确定性逆算法来实现稳健且高效的逆分析。通过使用数值模拟 IRT 信号和激光 IRT 实验获得的信号重建分层轮廓，证明了所提出的反演方法对于双层板分层缺陷的有效性、效率和鲁棒性。 基于该策略，不仅验证了该方法在IRT无损检测中的可行性，而且显着提高了反演重建分析的实际适用性。