Abstract: Modeling and numerical simulation of infrared thermal nondestructive testing (IR TNDT) for the thickness and its unevenness of thermal barrier coatings (TBC) are studied by the finite element method. The transient heat conduction of TBC structures is described by an axisymmetrical model in cylindrical coordinates, and the corresponding physical model and finite element model are constructed. The temperature field of the TBC structures stimulated by a heating pulse is analyzed by using the finite element analysis software ANSYS, and the relationship between the TNDT information parameters (such as the maximum differential temperature and maximum contrast) and thickness characteristic parameters (thickness difference and thickness) are explored. The results show that at a fixed coating thickness, the maximum temperature difference and maximum contrast are a nonlinear function of the thickness difference and they increase with the increase of thickness differences. At a fixed coating thickness difference, the maximum temperature difference and maximum contrast are a nonlinear function of the coating thickness, and they decrease when the coating thickness increases. The thickness difference and thickness of ceramic coatings can be evaluated inversely by the calculated relationship between the information parameters and the thickness characteristic parameters. These results provide theoretical support for the detection and characterization of the thickness and its unevenness of TBC by IR TNDT.

Key words: materials testing and analysis, nondestructive testing, simulation, thermal barrier coatings, thickness measurement, thermography