Experimental Study On Surface Flexible Rolling

Flexible rolling is a new continuous flexible forming technology for curved surface sheet parts. relied onthe characteristics of rolls’ bending shape and width of the roll gap can be flexible controlled, enables two-way bending of sheet parts, combined with traditional vertical plate rolling technology, can achievecontinuous and efficient forming of three-dimensional surface parts. Compared to other curved surfaceforming methods, flexible rolling method has an advantages with lower cost, wider range of shaping, betterforming continuity etc. Through adapting rolls’ bending shape and roll gap distribution, flexible rollingmethod can process different curved surface parts, meets the individual needs of surface sheet parts marketbetter. Thus, expanding the theory and experiment study about the flexible rolling, summarizing the forminglaw in flexible rolling experiment, have a great value in engineering research. The main contents andconclusions of this paper are as follows:1) Comparative analyze the rolls’ characteristics of traditional cold-rolled sheet metal forming and flexiblerolling, discuss the shapes of two typical roll gaps, analyze the forming results of which with metal plasticforming principle, obtain the reason of flexible rolling parts’ two-way bending which is the work rolls’transverse bending and the longitudinal residual compressive stress caused by uneven plate thinning.Investigate the geometric principles of flexible rolling process, point out the feasibility of the target curvedsurface parts derived the roll gaps’shape reversely, and compare the contact states of rolls and sheet metal intraditional plate rolling and flexible rolling, obtain the friction conditions and the distribution of contact forcein flexible rolling process. According to the centerline distribution function and the width function of theflexible rolling gap, derive the roll shape function of upper and lower rollers by polar coordinate conversionmethod, combined with the finite element method verify the effectiveness of roll shape function in numericalsimulation.2) Point out the key mechanical structures of the flexible rolling equipment according to its functions,and propose the experiment operation program. Summarize the mechanical clearance’ impact on adjustingshape mechanism’s precision, proposed an operation method to compensate the mechanical clearance, andanaslyze the vibration of working rolls, propose adjusting the working rolls’curvature justifiable to control the vibration. Meanwhile, simplify the roll-shape function and calculate the simpler roll-shape function whichis more convenient for experiment operation.3) Analyze the surface characteristics of convex part and saddle part formed by flexible rolling, obtainhorizontal and vertical cut lines of forming parts at different locations with reverse engineering methods andcomputer modeling software, verify the good uniformities of every five cut lines by fitting method, thenverify the feasibility of flexible rolling. As for the winkle defect, the error of adjusting will directly lead towrinkles on forming parts from the conclusion of experiment, propose a thickness control method to eliminatethe winkles and verified valid in the forming experiment.4) Experiment designed to study the effects of the forming speeds and the plate thickness values on flexiblerolling process, analyze the horizontal and vertical curvature trends when changing the process parameters.According to the experimental results, forming speeds has some influence on the curvature of the formingparts. Through the analysis of forming effects, summarize the range of best suitable forming speeds. In theplate thickness experiment, results shows that the thickness increasing causes inhibitory effect on thetranverse bending and longitudinal bending, related to the large deformation resistance according to theanalysis. Besides, there is a phenomenon in the forming experiment that plate thickness has some effect onflexible rolling parts’ winkles, combine the wrinkles forming theory in plastic deformation, the thicker thesheet, the greater the critical stress values of the instability which causes winkles, thus verify the accuracy ofthe experimental results.