Research On Numerical Simulation And Wrinkling Defects Of Continuous Roll Forming

Three dimensional curved surfaces with its flexible, reliable quality and have a wide range of applications in the automotive manufacturing, aerospace, shipbuilding, architectural design, art design and other fields. The traditional 3D curved surface forming method is mainly based on the mold forming, the forming precision is high and the consistency is good, while the efficiency of this method is lower, and the cost is higher. Some new three-dimensional curved surface forming process which suitable for small batch, single piece and short period of production in many fields of modern society has been put forward. In order to meet the market demand, continuous roll forming process is put forward.Uneven roll gap formed in continuous roll forming process using a pair of flexible roll, the sheet pass the roll gap under the rotation of the bending roll. The sheet produces lateral bending under the transverse bending roll. The non-uniform gap made uneven thinning in the transverse direction of sheets and the sheets produce longitudinal bending. The shape of different 3D curved surface parts can be realized by adjusting the shape of the roll gap, the cost is low, the efficiency is high, and the forming method is flexible. In the continuous rolling forming process, the control of the roll gap is the key to forming, and different selections of forming parameters has a great influence on the forming results, unreasonable parameters make the forming process difficult, even cause quality defects. In this paper the roll gap control method is described, the forming error is analyzed. The influence on the forming results of sheet thickness and velocity of roll and some other parameters in the forming process are numerically simulated and analyzed, which provide a basis for the experiment. This paper focuses on the wrinkling defect by numerical simulation and experimental, provide the basis for the optimization of continuous roll forming process.The main research contents and conclusions of this paper are as follows:(1) Established the modeling of numerical simulation of the continuous roll forming process, the quality of forming parts is analyzed. Through the analysis of shape of the parts, the quality of the parts is good in the horizontal and vertical direction. The forming error of saddle and convex parts is analyzed. In the saddle parts, the forming effect in the middle region is better, and the radius of curvature is smaller. The quality in the longitudinal direction of the formed part is changed from the middle to both sides. In different position, the forming quality is good. The smoothness of curve is better in the middle position in the transverse direction. From the start stage to middle of forming parts, the quality is good, better than that in the end position(2) The influence of some parameters on the convex surface parts is analyzed. The effect of thickness is analysis. The results show that increasing the thickness of the sheet, transverse and longitudinal curvature radius increases with the same thickness reduction rate. The bending degree reduced and the stress and strain also decreased. Under the condition of the same maximum thinning rate, with the increase of thickness, the curvature radius increases, the bending degree decreases, the transverse curvature radius increases, and the variation degree is not as obvious as the longitudinal direction. In the numerical simulation of different rolling speed conditions, the results show that increasing the rolling speed, the forming stress increases, equivalent plastic strain reduction. A large roll speed increases the longitudinal curvature and reduces the transverse curvature, and not good to the full deformation of the sheet material, and the forming quality is bad.(3) The wrinkling phenomenon in the continuous roll forming process is analyzed. Numerical simulation of some parameters of wrinkling are carried out. The wrinkling region is described, wrinkling is easy to occur in the edge area of the saddle parts, and easy to occur in the middle area of the convex curved surface parts. In the case of different maximum compression ratio, with the increase of the maximum compression ratio, the wrinkling in the edge region of the saddle parts and in the middle region of the convex curved surface is aggravated. Through the analyzed of effects of sheet thickness on the wrinkling shows that increasing the sheet thickness can effectively inhibit wrinkling. In the case of saddle parts, wrinkling phenomenon under the different radius of rollers are studied, a bigger radius of roller have certain inhibition on wrinkling.(4) Do experiments of continuous roll forming and compared the simulation results with the experiments results. The effects of continuous rolling forming speed on convex curved surface parts is carried out, small rolling speed can increases the ratio of transverse curvature of longitudinal curvature, easier to shape an obvious two-way curvature 3D surfaces. Wrinkling of forming parts under different compression ratios are studied by experiments of the convex surfaces and saddle parts. The middle position of the convex curved surface and the edge position of the saddle parts are easy to produce wrinkling at a higher compression ratio. Wrinkling degree is more serious in the experiment than that in the numerical simulation, but the wrinkling height increases with the increase of the compression ratio in both conditions, which verifies the prediction of wrinkling in the numerical simulation. Under the same conditions, the results show that the increase of the thickness of the sheet has a certain inhibiting effect on the wrinkling.