Influence Of Forming Zone On The Forming Result Of Three-dimensional Surface Part In Flexible Rolling

Three-dimensional surface parts are widely used in aviation,automobile,ship and other industries.Traditional die forming has the advantages of high precision and short production cycle.It is the preferred process for manufacturing large quantities of 3D surface parts with same specification.However,as the longer manufacturing cycle and higher production cost of die,it is difficult for traditional die forming to meet the demand of 3D surface parts with diversification and small batch.Flexible rolling is a novel forming process for 3D surface parts,which combines traditional rolling process with multi-point concept to realize flexible continuous surface forming.Based on the characteristics of this process,it can quickly and effectively meet the market's requirements for 3D surface parts with diversification and small batch.Due to the advantages of simple structure of forming equipment,low cost and smooth surface of forming parts,the process has a good prospect of application and development.At present,the flexible rolling technology is still in the developing stage,many problems need to be solved.In this paper,the influence of sheet forming zone on forming results of 3D surface part was studied by using the circular arc as roll gap contour,and the solutions to the problem of forming small curvature surface part were proposedThe main contents and conclusions in this paper are as follows:(1)The principle of flexible rolling and the forming process of 3D surface have been discussed;And the roll gap distributions of convex surface part and saddle surface part have been analyzed;In the forming process,the mechanical of sheet contact deformation area has been analyzed;The longitudinal bending deformation caused by uneven longitudinal elongation distribution of sheet metal has been studied;the roll gap functions of convex surface part and saddle surface part have been derived.(2)According to the process of flexible rolling,the corresponding finite element model has been established,and the boundary conditions and other related modeling parameters involved in this process have been determined.In this paper,a scheme for rapid configuration of roll gap distribution is presented,the forming process of convex surface part and saddle surface part have been simulated and the forming results are analyzed.(3)In the finite element analysis,the influence of the sheet forming zone on the forming results of 3D surface part has been studied,and the results showed that the quality of 3D surface part obtained by using circular arc as the contour of roll gap was better.With the increase of the longitudinal forming length,the stable area length of forming surface part increases obviously.With the increase of transverse forming length,the plastic deformation of forming surface part increases,the stable area length decreases,the thickness thinning precision decreases,the sheet thinning decreases,and the equivalent bending deformation increases.When the rolling reduction is constant,with the increase of sheet thickness,the plastic deformation decreases,the thickness thinning precision decreases,the sheet thinning decreases,and the equivalent bending deformation decreases.When the sheet thickness remains unchanged,with the increase of rolling reduction,the plastic deformation increases and the thickness thinning precision decreases,the sheet thickness decreases,and the equivalent bending deformation decreases.(4)The forming defects of small curvature surface part have been studied,and the flexible rolling asynchronous forming process is proposed by analyzing the mechanism of defects.The experimental results show that the asynchronous forming process can effectively improve the uniformity of forming surface part and increase the effective forming area length.By properly adjusting the friction between the upper,lower rolls and the sheet metal,the longitudinal deformation of forming surface part can be controlled and the forming error can be corrected.(5)For the problem of limited longitudinal deformation of small curvature surface part caused by machining hardening,the incremental multi-step forming process has been proposed,and the forming principle was analyzed.In the numerical simulation,the influence of incremental multi-step forming process on the forming results of convex surface part and saddle surface part is verified.The experiment shows that the forming defects can be avoided and the longitudinal bending deformation can be maximized by reasonably designing the deformation amount of each forming step.Making a reasonable number of forming times can improve the forming efficiency and reduce the forming period.(6)The experimental equipment and forming process of flexible rolling are described in detail.The measuring tool and operation procedure have been introduced,and the forming surface parts have been measured.By the error analysis of shape,thickness and longitudinal deformation of forming parts,the feasibility of numerical simulation in guiding experiment is verified.