Distortion of U-channel sections in plastic bending

When a thin-walled U-chnnnel section is plastically bent, considerable in-p lane distortion occurs. The initially flat base of the U is deformed into a circular are. The sides remain perpendicular to the base so that an angle between the sides develops. In this paper, an analytical expression for the amount of distortion is de,il ed based on energy minimization. The express ion is purely geometrical indicating that distortion should not depend on m aterial properties. The theory is compared with four-point bending experime nts of thin-walled channels, with good agreement found.