| Flexible roll forming (FRF) is a new process of forming method. Combined withmulti-point forming and roll forming, the basic principle is forming three-dimensionalcurves fast, continuously and efficiently by using flexible rolls, which are composed bythe uneven roll gap. The advantages are to reform the materials utilization rate, to widenthe forming range, to improve the forming effect. FRF can be easy to form thethree-dimensional curves parts, such as convex surface parts, saddle parts, disc parts andtwisted shape parts, etc. Studying the characteristics of FRF and developing the newequipment of FRF have a wider application space market and higher research anddevelopment value.In this paper, the finite element model of the flexible roll forming was established,and the model parameters are set for numerical simulation. The stress-straincharacteristics in the forming results have been analyzed. The influence of processparameters on the forming effect has been discussed. Some experiments have beencarried out to verify the plate forming conditions. Defects problem in the process offorming has been studied. Some ideas have been proposed to improve the formingexperiment.The main contents and conclusions are summarized as follows:(1) The principle and characteristics of FRFThe principle of FRF and forming equipment were described, and it shows thedifference between FRF and traditional rolling fundamental through the comparativeanalysis. The device and structural characteristics of FRF were introduced. Theadvantage is simple and easy to control, and fast and efficient to form. The shape controltheory was described, and using method of the sole tune-shaped process was proposed.As the theory basis of plate-shaped study, plate-shaped function, forming part thicknessand bidirectional primary curvature radius were deduced by using the geometricrelationship. (2) The establishment of the finite element model for FRFProceed from the elastic-plastic finite element solution, mechanical analysis wasperformed by using explicit dynamic finite element method for forming process. Thebasic theory of FRF numerical simulation was introduced, and finite element equationwas given. The finite element model of FRF was established, the related problems in theprocess of solving Model were processed. Experiment and numerical simulation wereperformed to form the convex curved part and the saddle part, and the simulated resultsand experimental results were consistent. It is proved the feasibility of FRF.(3) Numerical simulation for the process of FRFAccording to plastic deformation theory, it was explained the reason forthree-dimensional surface parts processing can be completed by F RF. The changes ofelastic-plastic curve were analyzed, and the minimum rolling thickness of the sheet wasdiscussed. The model of FRF was studied with mechanical analysis of stress and strainstate in theory, and longitudinal curvature calculation method was given by calculatingthe relationship of the rolling moment. Combined with the simulation result of FRF，stress and strain distribution characteristics were analyzed in the process of rollingforming parts. It illustrated the reasons for a two-way bending phenomenon and formingthe three-dimensional curves parts, and the correctness of the theoretical analysis andcalculation method was verified.(4) The stress and strain characteristics of FRFThe characteristics and process parameters of FRF were analysis in the numericalsimulation. According to the geometric characteristics of FRF, two-way bendingdeformation mechanism of the forming parts was analyzed, and process parametersaffecting the bending deformation were identified. According to the geometri calrelationship of the adjustment technology and two-way bending, the flexible roll contourwas calculated. Different process parameters were compared as the known conditions tocomplete the simulation experiments. The finite element numerical simulation ofConvex Curves parts and saddle parts were completed, and the results obtained wereanalyzed for stress and strain. Parameter conditions were different, and the results ofstress and strain distribution are also different. It can be able to analyze the c auses ofdifferent shapes sheet.(5) The shape analysis of FRFHere were some solutions to some important issues when forming experiment byusing the FRF experimental apparatus. Actual adjustment work was calculated detailed,and the inspection method was introduced for the flexible roller adjustment precision of experiment device. The processing method of three-dimensional optical scanner wasintroduced to measure the forming parts. Shape analysis was considered from theforming of transverse and longitudinal bidirectional. The regular was found out for thetransverse forming and the thickness changes, and radius of curvature change trend wascalculated and analyzed for the longitudinal forming. The shape analysis was carried outon the experimental results, which was compared with simulation and obtained similarconclusion. It verified the correctness and feasibility of FRF.(6) Numerical simulation of defects for FRFThe wrinkle defects and indentation defects were analyzed, which were oftenencountered in the process of FRF. The critical condition of wrinkling was summarizedthrough the analysis of forming a buckling deformation theory for wrinkle defects.Through the analysis of process parameters, the influences of the wrinkle on formingparts were interpreted for saddle parts as research subjects. The flexible rollerimprovement program of FRF was put forward to indentation defects, which is themethod of Local adjustment to the shape of flexible roller. Using weight factors tofine-tune flexible roll, indentation defects were able to suppress better for convex curvesparts as research subjects. The characteristics of the small deflection for FRF wereintroduced, and the criteria of surface fairing were used to verify the effect of formingparts. It is proved that the better quality of forming parts can be obtained by using thismethod. |
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