Thermographic Image Analysis of Fatigue Crack Propagation in a High-Alloyed Steel under usage of discrete fourier transformation and rigid body motion compensation

AbstractTo optimize the evaluation of thermographic measurements a lock-in algorithm with motion compensation was developed. Analysis showed that motion of the specimen could be compensated and therefore deformation of stress and temperature fields could be eliminated. Based on the compensated pictures a better identification of the crack tip is possible in both, the E-Mode as well as the D-Mode. Also the resolution for stress measurements especially in regions with high emissive gradients is enhanced. The values of the E- and D-Amplitude evaluation are strongly influenced by the motion compensation. Therefore this correction is essential for quantitative measurements