Davenport Iowa aluminum plate mechanical stress relief

Boeing/Alcoa aircraft wing plate, up to 50 ft long and 4 in. thick, mechanically stress-relieved by a multi-million-pound hydraulic stretcher that elongates the plate three percent in plastic deformation.

Every aircraft wing on every Boeing or anyone else's jet, when they make the aluminum plate in Davenport, Iowa — it could be four-inch, six-inch thick plate, and they quench it and heat treat it to get high strength — they have terrible residual stresses in that. And if you made that wing out of that material with those residual stresses, it would fatigue within hundreds of hours of operation. So they obviously don't do that. How do they stress relieve it? I've been to the room — it wasn't in operation, but they take that whole plate, that could be 50 feet long and four inches thick, and they have this three-million or ten-million pound machine, great hydraulic jaws, and they grab it and they stretch it three percent. They plastically deform it, and that relieves the residual stresses. So many of your aluminum alloys are stress relieved by adding mechanical stretching plasticity.