Research On One-Step Inverse Finite Element Method In Tube Bending

Metallic bended-tubes are widely used in aerospace,automotive,rail transportation and other fields because of the characteristics of high strength and light weight.With the rapid development of manufacturing industry,people put forward higher requirements on the performance of bended-tubes.The finite element numerical simulation method can accurately predict the bending performance of the tube,which could assist to improve the forming process,save time and economic costs.However,the incremental finite element method requires complete mold information,complicated operation and needs a long time to solve,so it has poor applicability in the initial design of the tube system.This paper presents an one-step inverse forming finite element method for tube bending based on the total strain theory.In this method,the straight tube blank is used as the initia l configuration,the known bended-tube is used as the final configuration,the forming process is considered as proportional loading.Establish ing the equilibr ium equation based on the virtual work principle,and solved it in a large step to predict the thickness and strain distribution of the tube.Considering the bending effect,the DKT12 shell element is used to divide meshes.The element stiffness matrix and the nodal internal force are derived.Based on the nodal displacement obtained by the one-step inverse forming method,the springback of the bended-tube is simulated using an implicit algorithm.The initial solution predictive technology of one-step inverse forming of tube bending is well studied.First,a regular mesh generation algor ithm is developed to automatically establishes a mesh model based on the key geometric information of the bended-tube.Then using a conformal parameterization method to solve initial tube blank node position;Finally,the grid smoothing algor ithm based on linear elastic reverse deformation is used to adjust the node position to obtain a high-precision initial solution.The one-step inverse forming program for tube bending is independently developed based on the above theory,and one-step inverse forming simulation are performed on a space bended-tube and a spiral tube.Compared with experimental values and simulation results of LS-DYNA and ABAQUS/Explicit,the high accuracy and efficiency of the program are verified,it also shows that the one-step inverse forming method of tube bending has engineering application value.