Stretch-bending formation method of lower enclosing rib of rectangular hollow section gun turret

The invention relates to a stretch-bending formation method of a lower enclosing rib of a rectangular hollow section gun turret, belonging to the filed of section plastic processing. The method comprises the following steps of: putting an elastic core iron into a rectangular hollow section blank, plugging one end of the blank by a plug, filling cohesive sandy soil to the other end of the blank, and plugging the other end of the blank by a plug after tamping; putting the blank filled with the elastic core iron and the cohesive sandy soil and provided with two plugged ends into two chucks of a stretch bender, and clamping and fixing the blank by using a rigid clamp; tightly compressing the upper and lower surfaces of the blank by using a clamping device; starting the stretch bender to apply pre-tensioned force at two ends of the rectangular hollow section blank; maintaining the pre-tensioned force and bending the rectangular hollow section blank along a stretch bending profile model; after bending, adding tensi