基于裂纹精细数值模型的应力腐蚀裂纹重构

Reconstruction of Crack Profile Based on a Fine Numerical Model of Stress Corrosion Crack

真实裂纹的反演重构是无损检测理论的难点之一。由于反问题的不适定性,在应力腐蚀裂纹(SCC)的定量重构中常出现裂纹深度的过小评估。根据SCC电导率的测定结果,采用裂纹区电导率分区域赋值的思想,建立了SCC精细数值计算模型,有效改善了SCC深度的欠评估问题。裂纹重构过程中,利用基于粒子群算法(PSO)和共轭梯度法(CGM)的混合逆策略,分别寻求裂纹的形状参数和电导率分布。数值模拟和实际涡流检测信号的重构结果,验证了所提出的模型和方法对于应力腐蚀裂纹重构的有效性。

Sizing of cracks is one of the difficult points of the quantitative nondestructive testing. For a Stress Corrosion Crack（ SCC）, the reconstructed crack profile is often underestimated especially for the parameter of crack depth because of the ill description of the corresponding inverse problem. In this paper, a fine crack model, which consists of a group of crack zones of different conductivity value, is proposed for the numerical simulation of SCC signals based on the measured conductivity distribution of a SCC. The reconstruction precision can be effectively improved by utilizing the new crack model and a hybrid inversion scheme of the Particle Swarm Optimization（PSO） algorithm and the Conjugate Gradient（CG） method. Reconstruction results from simulated and the measured eddy current signals of an artificial SCC demonstrate that the proposed numerical model and the inverse analysis scheme are effective for the sizing of SCC.