Research On Strip Deformation Behavior Of Multi-Roll Continus Straightening Processing

Roller straightening as an important process to correct defects after rolling is generally used to eliminate bending or twisting deformation caused by external force, temperature changes and stress evolution. The essence of the roller straightening on strip shape control is control of bending level and internal stress. Classic model assumes that the strip without initial stress and new residual stress will not be produced in straightening process, which has certain limitations to the precise analysis. This paper focuses on the stress evolution way in strip strengthening process, the residual stress and residual curvature are seen as the core to build a strengthening material continuous straightening model which is based on analytical method and numerical method, and different straightening strategies are deeply studied. The innovative conclusions obtained are as follows:(1) Stress evolution way and law in continuous elastic-plastic bending process are analyzed by using the basic principles of elastic-plastic mechanics. The results show that section stress evolution in continuous elastic-plastic bending process depends on deformation history, and the bending elastic-plastic analysis method considering stress transfer effect is more suitable for continuous straightening process. On this basis, the differences of bending properties between strengthening material and ideal elastic-plastic material are comparatively analyzed, and resilience ratio of the strengthening material is found greater, which is beneficial to maintain bending shape after straightening.(2) By using stress linear superposition principle, the stress distribution model in continuous straightening process is built and different straightening strategies are analyzed on this basis. The results show that compared to the small deformation straightening strategy, with the increase of bending frequency, the residual curvature fluctuates in a smaller range when the large deformation straightening strategy is adopted. Thus it is proved that the residual curvature control ability of the large deformation straightening strategy is better than the small deformation straightening strategy. Thus it is proved that the latter strategy is better than before(3) The large deformation straightening strategy due to the better residual curvature control ability is selected. The residual curvature quadratic convergence straightening program is proposed. Based on the improved composite trapezoidal integration, the bending deflection calculation method is established. Straightening process setting method which synchronously control section mechanical parameters and geometric imperfections is implemented.(4) The FEM model for continuous straightening process is established by ANSYS/LS-DYNA simulation software. Comparing the numerical results with the analytical results, longitudinal load and unload stress deviations along the section edge are respectively4.1%and9.31%. At the same time, the data of straightening force is collected by field test and moment ratio curve is calculated. The deviation is within13%compared to the analytic results. Accordingly the correctness of stress distribution model for continuous straightening is verified from both numerical simulation and field experiments.