Simulation Method For Three-dimensional Stretch-bending Forming Of Car Door Sash

Variable curvature parts with less residual stress can be produced by stretch-bending technology which has quite a few advantages.Stretch-bending technology are broadly involved in vehicles,railway vehicles and aeronautics and astronautics because it’s characters that hollow inside,thin wall,high strength,long longitudinal length,big bending radius and very strict with the shape of stretch-bending parts.Car door sash is a variable curvature part that made by three-dimensional stretch-bending.It’s cross-section will deform severely and have a bad seal performance because unreasonable design.In order to predict the cross-section deformation in advance,shorten the product design cycle and cut the cost,first of all,non-linear constitutive relationship was considered.A method that simple experiment combined with finite element analysis was introduced to identify the parameter in the constitutive equation.And the hardening curve from parameter identification was compared with the hardening curve from numerical fitting.The car door sash’s three-dimensional stretch-bending and spring-back analysis model was established by means of the commercial code ABAQUS which apply dynamic explicit FEM and static implicit FEM.Furthermore,the element mesh,boundary conditions in model building process were discussed.Most importantly,the spring-back was considered before the cross-section deformation results were extracted.The stretch-bending experiments were conducted to check the analysis model of car door sash A.The stress and strain distribution in each step and thickness alteration in the direction of length and on the cross section were analyzed,the material flow regulation and forming mechanism were investigated.Aiming at the problem of choosing the best design from many schemes of car door sash,the cross-section deformations of six schemes car door sash were predicted by means of above three-dimensional stretch-bending analysis model.Weighted mean square error（WMSE）was introduced into the cross-section deformation evaluation system,and problem of choosing the best design from many schemes of car door sash was solved.The influence of four main manufacturing parameters(namely bending angleθ,height difference from start to the end of the profileΔ_H,spot size D_SP and spot interval I_SP)on stretch-bending cross-section deformation was investigated.Orthogonal test was designed.And the order of influence on stretch-bending cross-section deformation are bending angleθ,height difference from start to the end of the profileΔ_H,spot size D_SP and spot interval I_SP.Also,the relationships between size alteration in the cross-section and two main craft parameters were discussed.To sum up,the analysis model of car door sash’s three dimensions stretch-bending established in this paper can be used to the analysis of car door sash stretch-bending.