Research On The Springback Of Anticlastic Double-curved Part Forming

Springback of sheet metal forming causes part size and shape changes after releasingelastic energy. Springback is an inevitable physical phenomenon in sheet metal formingprocess, which seriously effects the size and shape accuracy of stamping parts. For the pastmany years, people have been done their best to research the rules of springback to predictand control itself. With the development of industries, Sheet metal forming is no longeremployed in the manufacturing of simple two dimension shaped parts, but parts withcomplicated three-dimension surface, also high strength steel which is wildly used results inmore obvious springback. As a kind of typical three-dimension sheet stamping surface, doublecurvature surfaces are involved in field of automobile and aerospace, and springbackresearches of double curvature parts are almost concentrated in the situation of synclasticcurvature，rather than anticlastic curvature.Therefore, experiments, computer-aided detectiontechnology (CAT), as well as finite element simulation were adapted conjunctively to explorethe anticlastic curvature parts. The preliminary rules of springback of this kind part wereobtained, so as to improve the forming quality and production efficiency of stamping parts. The main contents are as follows:1. Springback experiments of anticlastic double-curved part forming were designed andcarried out, Grating of non-contact measurement technology was employed to obtain thecoordinate data of parts surface, and the rules of springback in two main vector direction ofthe anticlastic double-curved part was achieved.2. The relationship between springback with the curvatures of the part were explored, acharacterization method of springback through measuring the local curvature was described.This method can be better reflect the physical nature of springback, it will avoid springbackevaluation mistake caused by parts matching error when using displacement as a target, andbe more conducive to springback compensation calculation of die surface. Gaussian and meancurvature changes of the plate reflect the role of membrane force and bending moment,experiment results show that membrane force has a very important impact on the process ofanticlastic double-curved part springback.3. Finite element model of forming and springback of anticlastic double-curved part was established in ABAQUS, and the influence from constitutive model in springback calculationwas analyzed, which was combined with the experiments. Results show that yield criteriamakes an important difference on the calculation of the parts springback, and anisotropicyield criteria can be better describe the deformation behavior of the sheet metal than isotropicyield criteria.4. Based on the experiments and numerical simulation, the effects of unilateral curvatureand bilateral curvature ratio of the experimental dies on the springback of anticlasticdouble-curved part were analyzed. Results show that springback and membrane force in thedirection of the small radius of curvature which is led by membrane force, are reduced withthe radius of curvature increases, while springback in the large radius direction which is ledby bending moment is increased with the radius of curvature increases. Moreover, when theratio with double curvature is increased, springback in the smaller radius of curvaturedirection get smaller, but larger in the larger radius of curvature direction. The effect ofcurvature on springback from the work has good theoretical significance of the anticlasticdouble-curved parts springback compensation in engineering production.