Disclosed is an exemplary test apparatus having an autoclave head, a fretting mechanism connected on a first end to a first side of the autoclave head, a load train operably connected with a first end of the fretting mechanism, an autoclave adapter connected on a first side to a second side of the autoclave head, and a force balance assembly connected to a second side of the autoclave head and configured to equalize a pressure acting on the load train. Certain exemplary embodiments include an upper plate, a plurality of upper tie rods connected to a first side of the upper plate and a second side of the autoclave adapter, a lower plate, a plurality of lower tie rods connected to the first side of the autoclave head and a first side of the lower plate, and a pressure vessel sealingly connected to the first side of the autoclave head.