Factors Causing Undesirable Deformations during the Bending of Extruded Sections

The authors have investigated the factors causing undesirable deformations of extruded sections subjected to a quasi-uniform bending moment. These deformations include flattening distortion, wrinkling and folding. In this report, the basic mechanism of the flattening distortion of the cross section is explained and effective methods for controlling the undesirable deformation are proposed. The flattening distortion appears as a primary deformation at the beginning of the bending operation and corresponds to the shape of the cross section and the degree of bending. It is clarified that the thickness of the wall, the shape of the cross section and the position of the neutral axis influence the configuration of the flattening distortion. As an example, the bend degree of the wrinkling limit is approximately fourfold when the thickness of the workpiece is doubled.