In the 1980s I had a job detecting cracks a metal forgings. We can do X ray analysis of forgings! The cracks in the forging funnelled the X rays in a line, and this exposed the cracks as a white line!
We also applies high power ultrasound. This also displayed crack so as white lines, though we had no idea why! On my PH D in 2001 I thought up the idea of molecular nuclear fusion. This turns molecular hydrogen into helium and molecular fragments. We have water this is helium and oxygen gases, with gamma wave radiation! This exposes photographic film!
If we apply the ultrasound through a transfer medium, which is or oil or water, any crack in the forging will act as a stress concentrator! The bulk ultrasound is chosen to be below the level required to serve molecular nuclear fusion in the transfer media.
As a crack in the forging we will get molecular nuclear fusion! With gamma wave emission. Which will expose light excluded photographic film. So we get an exposed line along the line of the crack.
Every person alive today announce their life to ultrasound setting of molecular nuclear fusion. Green crops in light use ultraviolet light to set off molecular nuclear fusion, which we call photosynthesis! It turns water into helium and oxygen gases, plus gamma wave radiation: go figure.
A beating animal hearts also does molecular nuclear fusion. Which is why we breathe out helium and free radical oxygen, while emitting gamma wave radiation-A sure sign that nuclear processes are occurring.