Explicit FEA of Stretch Bending of Aluminium Bumpers

Stretch bending is an important method for plastic forming of aluminium extrusions to some desired curvature. The industrial application of the process is, however, not always straightforward. Tolerance demands to the final product and production efficiency require proper control of possible difficulties such as cross sectional deformations and unloading springback. Traditionally, trial-and-error and in-house experience have provided information for necessary process adjustments. The developmentof numerical tools such as the Finite Element Method (FEM) offers new possibilities for attaining further and more generally applicable knowledge on the stretch bending process. However, numerical simulation of forming processes is a rather delicatetask involving large deformations, material non-linearities and contact challenges. Therefore, laboratory test data must be used to validate the numerical model. Sections of a generic bumper were thus studied in a stretch bending rig. The numerical simulations using LS-DYNA applied two different anisotropic yield criteria proposed by Hill in 1948 and Barlat in 1997. Considering sagging and springback as the main response parameters, satisfactory agreement was found between test results and numerical predictions from LS-DYNA, but the Barlat criterion predicts the local deformations of the cross section most accurately.