Modeling and simulation of thermal NDT of three-layered structures by finite element method

Modeling and computer simulation of thermal nondestructive testing (TNDT) of three-layered structures are studied based on the finite element method (FEM). The TNDT mathematical model of three-layered structures is constructed in cylindrical coordinates, and the application of FEM to solving transient heat conduction problems in the cylindrical geometry is discussed. The evolutions of TNDT informative parameters versus defect size and depth are simulated by using the FEM analysis software ANSYS. The basic relationships between defect parameters, such as radius and depth, and chosen informative parameters, such as maximum differential temperature and maximum running contrast, are thoroughly explored to obtain some simple regression expressions. It is shown that, at a fixed defect depth, maximum differential temperature is directly proportional to defect radius, and maximum running contrast is linear to defect radius. However, if defect radius is fixed, both informative parameters become non-linear functions of defect depth. It is believed that obtained results may help engineers in developing a TNDT strategy for aviation bonded aluminum panels.