Square and rectangular cold-worked tubes are highly economical elements of the structures ensuring highly favorable relations between bearing ability and corresponding structure weight under such loads as twisting, buckling and lateral bending. Shaped tubes are widely used in a variety of fields such as civil and industrial engineering, fabrication of diverse metal structures, bridge spans, frames and racks, in motor-car industry, in building carriages, cranes, buses, agricultural machinery, parabolic-reflector aerials, bearing structures of gymnasiums, etc. All this predetermine high requirements to the dimensional accuracy of the finished shaped tubes and their reliability in operation. The reliability is determined by metal quality and the stressed and strained condition of the finished section resulted from cold shaping of the starting round tubes. It should be mentioned that the stressed and strained condition of the starting tube during its cold shaping is extremely irregularly distributed across the perimeter of the shaped tube, i.e. tangential stresses and strains are highest in the interior corners of the shaped tube section and considerably lower in its flanges.
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