Light gauge channel steel is fabricated from a steel sheet by roll forming. Cut end deformation of the channel steel was investigated by experimentation and three-dimensional finite-element simulation. During roll-forming, concave, convex, and reverse bending deformations on a flange occur and cause bending lines to diverge from the point of contact between the top roll and the flange corner. The reverse bending deformation is caused by a bending moment and a twisting moment. These moments remain on the flange. When the channel steel is cut, the release of the bending moment results in opening at both the top end and the tail end. Then, the release of the twisting moment makes the flange close at the top end and open at the tail end. Deformations at the tail end open widely with the overlap of the two moments.
A square steel pipe is reshaped from a welded round pipe by roll forming. We investigated the effect of the roll diameter on the crosssectional size of the square steel pipe by experimentation and three-dimensional finite element (FE) simulation. When the diameters of the top and bottom roll pairs are larger than those of the pair of side rolls, the cross section width of the formed pipe is less than the height. To equilibrate them, we perform finish forming at the final stage. Furthermore, the width of corner part of the formed pipe is greater than its height. The difference between these two sizes of width and height of the corner part in the final product is greater than those at upstream stands and increases with the ratio of the diameter of top and bottom roll pairs to that of side roll pairs. Offset the smaller roll pairs upstream makes the pipe square. Such offset is effective for producing pipes with equal width and height at the corner.
Square steel pipes are reshaped from welded round pipes by roll-forming. Pipe end deformation after cutting of the square steel pipe was investigated by experimentation and by three-dimensional finite element simulation. Each direction of the residual stresses composed of longitudinal stress and longitudinal-peripheral shear stress becomes reverse with respect to the outer and inner surfaces. A large opening deformation arises at the back end of the product by the release of those residual stresses. The side part receives bending deformation in the surrounding area of the contact zone with a roll. The residual stresses comprising longitudinal stress and longitudinal-peripheral shear stress increase as a result of the reverse bending deformation downstream of the roll center position. The absolute value of residual stress decreases with decreased initial wall thickness.
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