4.2. Bending and residual stresses
The residual stresses are another concerned issue for evaluating
the quality of the leveled H-beam. However, the residual stresses
are unavoidable due to the complicated elastic–plastic deformation
in the leveling process. The bending and residual stresses in the
flange andweb direction can be obtained by using the presented procedure,
as shown in Figs. 18 and 19, respectively. The heavy solid
lines whose color match the color of rollers at the top of the figure
represent the bending stress while the fine lines represent the residual
stress under roller i. It can be seen that the bending stresses distribute
in ‘X’ shape. The main reason is because the outer layers are
forced into plastic deformation while the inner layers are still in
the elastic range. Also, the leveling process is a continuous bending
process. Therefore, the bending stresses of the H-beamby each roller
are related to its residual stresses in previous bending. It means that
the bending stresses are not independent. Meanwhile, it can be
found that the bending stress still increases even though the fibers
are forced into plastic deformation. This is because of the strainhardening
effect.