Study On Defect Control In Tube Stretch-bending

Stretch-bending process is widely used in automotive and aerospace fields because of its small springback.Stretch-bending process plays an important role in China’s basic industry.However,accurate prediction of stretch-bending springback and section distortion has become an important problem in academic research and practical production.At present,with the promotion of national key research projects in the ’ 14 th five-year plan’ and the vigorous development of aerospace,automobile and other high-tech fields,higher requirements are further put forward for the products formed by stretch-bending of pipe type materials.Only by further studying the stretch-bending springback theory of pipe type materials can we meet the new challenges.In this paper,the classical kinematic hardening material model is taken as the constitutive relation,and the rectangular tube profile is taken as the research object.Based on the plane section assumption and the unidirectional stress assumption,the theoretical analytical model of the rectangular tube bending with polyurethane elastic material added inside is established.The mechanical models of ’ no reverse plastic compression deformation in the inner layer of rectangular tube ’ and ’ plastic compression deformation in the inner layer of rectangular tube ’ are established.Based on the strain superposition principle and the internal force load balance relationship,the expressions of the curvature radius and the total bending moment of the strain neutral layer of the two deformation types are derived,and the corresponding determination conditions of the two deformation types are obtained.The curvature radius of the geometric center layer of the rectangular tube after springback can be obtained by combining the plane stretch-bending springback equation.The analytical method of stretch-bending of rectangular tube profile was established.The finite element model of rectangular tube filled with polyurethane was established by Abaqus finite element simulation software.The influence of different tension and bending radius on springback,section distortion and wall thickness thinning rate of rectangular tube was analyzed.The law shows that when the bending radius is the same,the springback rate of rectangular tube decreases with the increase of tension,but the section distortion degree and wall thickness thinning rate of rectangular tube increase.With the decrease of bending radius under the same tension,the bending springback rate of rectangular tube decreases,and the section distortion degree and wall thickness thinning rate of rectangular tube increase.When the bending radius is too small,the thickness thinning rate of rectangular tube wall is too large,which affects the forming quality of rectangular tube.Taking 6005A(T5)rectangular tube profile as the object,the experiment is carried out on the rotating arm stretch-bending experimental machine.It is verified that the influence of the change of experimental conditions on the stretch-bending springback rate,section distortion and wall thickness thinning rate of rectangular tube is consistent with the finite element simulation;Comparing the experimental and theoretical analysis results,the accuracy of springback analysis prediction is given,which proves that the theoretical analysis of rectangular tube stretch-bending has a certain application prospect.