A Novel Multiphysics Sensoring Method Based on Thermal and EC Techniques and Its Application for Crack Inspection

Crack inspection is a critical issue in quantitative nondestructive evaluation (NDE). The eddy current (EC) method is effective for surface discontinuities detection, but the spatial resolution of conventional EC method is constrained by the size of EC probe. The photoinductive (PI) imaging method is a NDE technique that combines EC and laser-based thermal imaging methods. It had been clearly demonstrated that PI method is a high-resolution technique from practical experiments. In this paper, the numerical multiphysics simulation of PI imaging have been performed with 2D transient using the finite element method (FEM) to characterize corner cracks at the edge of a Ti-6Al-4V bolt hole specimen. The FEM simulation results of 0.25-mm, 0.50-mm, and 0.75-mm rectangular notches are showed and discussed. The results show that the PI imaging has higher spatial resolution in the area of the defect in 2D models as compared with the conventional EC images. We demonstrate that the PI method is a novel sensoring method for characterizing the geometric shape of cracks.