Investigation on the Suitability of Laser-excited Thermography to Detect Cavities in Metallic Components

摘要

Active thermography has become a widely used technique in nondestructive material testing and numerous excitation sources are applied. One field of application is the testing of joints. Especially the detection of defects in welds is a challenging tasks as two-dimensional defects like cracks can occur as well as volumetric inner defects as cavities. Recently, the suitability of lasers as a contadless excitation source has been investigated and it was shown, that cracks can be detected. As the specimens are locally heated, a heat flow is initiated. Those heat flows can be used to detect crack-like defects that are perpendicular to the surface. However, the suitability of the laser-excited thermography to detect inner defects like voids and the influence of geometric as well as excitation parameters on the test result has not been fully investigated.