| Springback in profiles bending constraints forming accuracy, production efficiency, processing costs, and even influences the design profile processing equipment. It is a difficult and hot metal plastic working. springback is widespread in molding profiles. In recent years, with advances in technology, springback control has played a great development. But more research on the process of control the rebound, and rebound theory research is in seldom. If you do not fully understand the process of ship profiles rebound problem, needing to repeatedly fill curving profiles or correction. This will lead to increase production costs and production cycles. Around the profile bending springback problem, the main contents and conclusions of this paper are as follows:(1)Based on elastoplastic theory, from two aspects of bending stress and rebound stress, The paper has analyzed and elaborated springback mechanism, and has deduced ship profiles bending springback prediction formula. Taking the T profile as an example, thought Stress and strain curves of Q235 steel measured by experiments, with numerical software MATLAB, The paper has studied the moment variation with the increase of the curvature in the different axial tension force. Result shows: the axial tension will increase the bending curvature of the profile under the same bending moment. At the same time, the axial tension can also reduce the amount of rebound, and then writing the MATLAB program to solve the deflection curve of typical boundary conditions of ship sections of large deflection bending. The research results have certain theoretical significance and practical value.(2)The paper has built the finite element model of a shipyard frame bender to simulate the profiles forming process, analyzed the stress distribution after loading and the residual stress distribution after unloading rebound. In addition, this paper has also studied the influence of forming parameters on the rebound, such as concentrated load, loading time, mould clamping force, mechanical properties and geometrical size of profile. Result shows:concentrated load can reduce the rebound, the load time has little effect on the springback, the clamping force of the die can reduce the resilience, the springback of high strength steel is greater than that of low strength steel, the springback of the Profile with big the height/width ratio is greater than that of the small one. Research results for the factory that is also based on the experience of workers in the control of springback have a guiding significance.(3)The finite element analysis results have shown that relationship of the bending curvature and springback curvature is linear, then linear fitting on the bending curvature springback curvature, regressing the multiple sets of data on the coefficients of the linear fitting which obtained from finite element analysis, getting the T profiles, L profiles(angle) of springback prediction formula.(4) The paper has compared the values of the finite element calculation, the theoretical and experimental. Comparison results show that both the finite element calculation and the theoretical calculation predicting the springback are correct.In addition, the results of the finite element calculation and test are more consistent, but the theoretical value is larger, and the theoretical value is higher than the experimental value.(5) Gradually approaching bending is one of the main methods of springback Control in the profile bending automatic processing. The prediction of the forming and springback of the first step is obtained by the theoretical formula, As the theoretical formula can only predict the rebound trend, there is a big error in the prediction of springback value, and the accuracy is much less than the finite element simulation. Therefore. The author proposes to predict the first step forming and springback by using simulation values. On this basis, then approaching bend, it can reduce the number of approximation, even up to forming once. |
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