Bob Cranz is correct, this would work for cracks in the rod, even when
it was attached at both ends. When rod fails, where does it fail, I'd
bet at the ends where TDR would be harder.
Given identical types of ends and repeatedly stressed, any engineer
would expect that solid rod would fail before cable type. A crack in a
single strand of wire cannot propogate anywhere except in that strand.
A crack in solid can go all the way through and probably will because
the crack itself becomes a stress concentrator.