Thermographic Testing
A non-destructive method for detecting internal flaws or inhomogeneities through the analysis of surface heat flow distributions using infrared cameras.
Thermography is basically a thermal image. The camera shows you the temperature distribution on the surface, and from that you can infer problems in the material or the weld. Watch for uneven heating or cooling; that often indicates defects like cracks or lack of penetration. It's important to set the camera correctly and pay attention to the emissivity of the material, otherwise you'll measure garbage. And remember: the image only shows surface temperature; what's underneath you have to infer from the temperature profile. Run the part in a calm area, without the sun or a draft Brass with it, then you'll get usable results.