"Ignoramus8008" wrote in message

OK, seriously: I can deflect this plate enough to become straight,
temporarily. As soon as I remove the deflecting force (forklift or
jack with chain), the plate returns back to original position.
The "ridge" goes along the longer dimension
i

You need to deflect it past straight until it yields. If you have a
way to measure the distance moved and the bending force, like the oil
pressure in a jack, you'll see and maybe feel the force stop
increasing when you reach the yield point of the metal.

I straightened some scrap channel iron by chaining the crooked piece
to two others in the center of the curve and jacking one end apart a
measured distance, increasing the distance by small increments until
the single piece was straight by eye after releasing the force. This
needs to be done carefully with everything safety-chained together as
~2000 lbs of force stored a lot of crossbow spring power in the steel.

Perhaps you could shim up one edge of the plate and drive the truck or
forklift to a mark near the center, slowly increasing either the
shimmed height or the distance you drive the vehicle as long as it's
more than heavy enough. If the plate hits the floor under the wheels
you control how far you bend it by the shim height, without having to
fine-tune the weight of the vehicle.

jsw