Research On Simulation Of Roll Forming Based On Mixed Hardening Model

Roll forming is a kind of plastic forming process in which a steel strip is bended by several sets of rolls gradually into the desired shape. The products are cold roll forming steels with various sections. Compared with hot-rolled section steels, they have significant advantages in energy and material saving, good surface quality of product, high dimensional accuracy, high relative stiffness and strength. Roll forming technology has been increasingly applied in the fields of building, transportation, machinery, electric appliance etc.Roll forming is a complex deformation process, which involves large displacement, finite strain and the problems of contact and friction between strip and rolls. This process exhibits obvious geometry, physical and boundary nonlinearity. So it is difficult to understand the forming rules. The edge of strip undergoes not only alternating deformation of tension and compression along longitudinal direction, but also cyclic loading-unloading along cross direction in roll forming process. Bauschinger effect has obvious effect on roll forming process.This thesis develop a finite element model of strip roll forming process and simulate the whole process of roll forming of ?°U?±section and ERW pipes. Based on J2 plastic theory and radial return stress update algorithm, an isotropic hardening coefficient was employed in elastic-plastic constitutive relation and a mixed hardening model combined with isotropic hardening and kinematic hardening was developed. The effect of hardening model on roll forming simulation was studied.In this thesis, based on the development technique of VUMAT, Fortran language was employed to develop a module for the mix hardening model on ABAQUS/Explicit software platform. The VUMAT subroutine shows correctness and accuracy through cyclic bending-unbending benchmark test.To study the effect of material hardening model on the forming process,...