Ken:
One test that we ran consisted of bolting panels to a merry-go-round type of contraption, and bending the panels, letting them "twang" back into place as the whole thing rotated.
Bolts/flat washers/split ring lock washers/and the type of locking nut that is deformed were all used. Every one loosened up within 24 hrs, no matter how tight we torqued them. The solution?
Nuts with nylon in them as locking nuts. (Nyloc nuts) They were used a maximum of 2 times when replacing the panels. Replace a panel a 3rd time? Replace the nuts too. Never had another panel loosen up.
