Definition of "FATT"

However, after 5% strain, all the Charpy values for grade A were still above 27J at +20°C, as required by the LR Rules and the mean crystallinities were all below 50% indicating that the FATTs for all the plates remained below ambient temperature.

2002, D. Francois, A. Pineau, From Charpy to Present Impact Testing, Elsevier Science, page 397