Real-time approach for thermal non destructive testing

The work presented in this paper has the goal to derive equations that permit experimental design of active non-destructive infrared testing. The approach consists of the predetermination of the required frequency for the input thermal signal given the size of a variety of possible defects in materials and the time when steady state response can be recorded. Infrared testing is known for the ability to give thermal images that are influenced by inner defects. For this reason, in the proposed approach the model used for the experimental design of non-destructive infrared active testing of materials is reduced from full three-dimensional (3D) to one-dimensional (1D). It is considered that, in some specific conditions, relevant results can be obtained before reflected thermal waves from more remote boundaries arrive back to the point under investigation. The analysis starts with the formulation and solution of the direct problem for three-dimensional (3D) heat conduction problem, followed by detailed development for the one-dimensional (1D) problem and ends with simulation results that illustrate the usefulness of the pre-determination of the frequency of the input thermal signal needed for the investigation of possible defects in materials.