Modeling and Simulation for Crack Detection in Aluminum Components Using Tone Burst Eddy Current Thermography

Tone Burst Eddy current Thermography (TBET) is a new hybrid, non-contacting, nondestructive evaluation method with a wide range of applications including aircraft. Aircraft can have structural cracks or other defects which can lead to failure. The safe life of structural members can be evaluated by determining the size and orientation of critical cracks. For understanding cracks, fundamental knowledge about the induced current density distribution in the component under test is required. Further, this information enables us to find the amount of heat produced at those locations and how it diffuses to the surface. This paper describes simulation work done for crack detection in aluminum samples. 3D simulation results have been achieved by using COMSOL multi-physics with AC/DC module and general heat transfer. Various parameters considered in this study are i) induction coil dimension, ii) plate dimension and iii) time of excitation for a particular crack. A comparison of results obtained by varying the above mentioned parameters is done. Numerical simulations are carried out in a plate with a part crack also. At crack edges, induced current is seen concentrated thus indicating a localized high heating in those areas relative to other regions. TBET method was found well suited for the detection of service induced cracks, usually caused by either fatigue or stress corrosion, with a high degree of sensitivity. .