Fig. 13: Comparison crack
propagation process for two patched specimens under fatigue loading
monitored from the metallic and the patched side
Understanding the interaction between local patch detachment and crack
growth in the structure is one essential goal in the patch design
process. To find out, how these two effects influence one another can
lead to improved design methods. Therefore, additional investigations
using optical LT are made for the specimen that is monitored from the
patched side. A comparison of the thermal images gained from passive IrT
and phase images resulting from LT measurements are displayed in
Fig. 14.