Research On Simulation Of Flexible Roll-forming Based On Non-linear Rotational And Kinematic Hardening Model

Flexible roll forming is a new kind technology of roll-forming. In this process, a group of removable gradually varied profile rollers are controlled by computer system, and by using configuration and control of various roll profile, component with complicated and variable section can be manufactured.The forming mechanism in flexible roll forming is more complicated than traditional roll forming.In the forming process, the edge of the sheet not only commutative deformation of tension and compression along longitudinal direction, but also cyclic loading-unloading along transverse direction, therefore, the Crossing and Bauschinger effects have obvious effect on flexible roll forming. According to the technology characteristics of cyclic loading-unloading during flexible roll forming, non-linear rotational and kinematic (RIK) hardening model was proposed to consider the Crossing and Bauschinger effects.Based on RIK hardening model and Barlat2000 yield criterion, the Flow Equation of the constitutive model was derived and FORTRAN language was employed to develop the secondary development for ABAQUS user subroutine VUMAT, and finite element program of RIK hardening model was achieved. Flexible roll forming process was simulated on ABAQUS/Explicit software platform, and effect of hardening model on stress and strain of flexible roll forming was studied, simultaneously a critical wrinkling stress analysis model and a sheet wrinkling criterion in flexible roll forming was established to reveal the influence of the material parameters and forming process parameters on wrinkling.For the material Docol Roll 1000 and DDQ steel, based on RIK hardening model, the stress and strain is more close to the theoretical and practical value than the isotropic hardening model. Because of the anisotropy axis of DDQ steel has a higher rotation rate than Docol Roll 1000, so the material RIK hardening model is more suitable for DDQ steel. In order to reduce or avoid the phenomenon of wrinkling instability in flexible roll forming, method such as reducing the flange widths, increasing the sheet thickness, or increasing the radius of the outer edge of convex can be employed. The critical wrinkling model presented can facilitate to determine whether the wrinkling occurs, the establishment of wrinkling limit diagrams can provide reference and information for the actual production of flexible roll forming.