Accuracy of 3d thermo-tomography model for the evaluation of aerospace components

Slowly but surely, more and more automated thermography measurement is being applied in industry. Thermography provides a high sensitivity for most defects, high accuracy in locating defects and mostly used in reflection mode, which is important for complex and large aerospace components. Furthermore, due to focal plane array detector, a large area can be measured comparatively in much less time than ultrasound inspection. By measuring components (< 6 mm thickness) with thermography the load of water coupled ultrasonic machine can be relieved. Recently, for the first time FACC [2] has qualified thermography inspection method for CFRP components and has reduced the inspection time up to 50 %, although measurement is conducted manually. Already in 2012 [1], DLR Augsburg carried out the automated thermography measurement of an aircraft structure and published the results. Since then, both the automated measurement process and the evaluation process have been continuously improved. To reduce the evaluation process time by means of 3D visualisation model for a large number of 2D thermography images, 2 independent methods [3] are developed at DLR. A further development of the evaluation process for both methods occurred first by generating a 3D-thermo-tomography model [4] (Measurement results according to their thermal depth). The defect analysis with this generated model takes place directly in the CAD environment. Along with their development phase accuracy of system components for two methods were analysed [5] within the scope of those respective test series. Moreover, experiments were performed for complete evaluation (the absolute and relative system accuracy between two methods), and 3D thermography models were generated with both methods to analyse visualisation accuracy of 3D model in CAD environment. The results are discussed in this paper.