Study On Optimization Of Loading Curves Of Variable Blank-holder Force In Metal Sheet Deep Drawing

With the rapid development of automobile industry and the transformation upgrading of traditional manufacturing, sheet metal stamping products were highly valued by their own unique features. The blank-holder force(BHF) control technology is a simple and effective technique which can effectively improve the sheet metal deep drawing quality and formability. Experimental results show that take advantage of variable blank-holder force (VBHF) can reduce or even avoid the instability phenomenon such as wrinkling and forming effectively, improve the stability of sheet metal’s forming. The advantage of VBHF is more obvious, especially for some products stamping in higher surface quality, larger dimensions, complex structure. However, today the research of VBHF still stays on the experience summary and numerical simulation, the specific influence mechanism is not clear, related research results are differ in thousands of ways, sometimes are contradictory. So, applied the research of the VBHF control technology and artificial intelligence technology in complex stampings forming has obvious practical significance to shorten product development cycles, rapid response to market, improve product quality and precision.In this paper, based on the relevant research projects, combined with the finite element simulation technology and artificial intelligence technology which application in the field of sheet metal deep drawing, take the asymmetry square box as the research model, according to the plastic forming theory and sheet metal stamping principle, analyzed the technological characteristics, common failure forms and evaluation standard drawing of the square box stamping; Established a theoretical mathematical model for square box forming BHF, analysis the stress and strain of the flange portion and the side wall portions, deduced the pressure wrinkling and rupture’s solution formula, calculated and determined the safety limits of VBHF loading in stamping and the safety drawing area for square box stamping.Secondly, make the use of professional CAE simulation software DYNAFORM simulated the deep drawing of square box, studied and analyzed the square box deep drawing performance under several typical variable blank holder force such as constant model, linear increment model, linear regressive model, ∨ mode and ∧ mode, based on the anisotropy theoretical of Hill, references related research, on the basis of the practical production requirements, researched and analyzed the effect of the VBHF in sheet metal’s limit drawing ratio(LDR).Then, written a simulation program by using the MATLAB software, established the RBF network intelligent forecasting model for VBHF loading in square box deep forming process. In view of the fact that the equilibrium and dispersion characteristics of the sampling data in the practical production, with the method of orthogonal test, obtained the studying sample data related to predict required by simulating of DYNAFORM software, training of the RBF neural network prediction model. Test the performance of intelligent network model by V VBHF simulation results and the network predicted results.Finally, comprehensive analyzed the results of network prediction and simulation results, polynomial fitting the neural network prediction results which forming better, got the optimal VRBF load curve for square box deep drawing. And the load curve is non-linear changes, more in line with the objective reality of sheet metal stamping.