Numerical Simulation And Experimental Study Of Springbacks On The Multi-point Forming Of Sail Surfaces Under Force-displacement Separated Control

Multi-point forming (MPF) has been applied to many aspects of social productionfor the advantage that the forming surface is reconfigurable. Nowadays, a lot ofresearches about MPF of cylindrical surface, spherical surface and saddle surface havebeen done and the corresponding laws of forming have also been discovered. Byanalyzing the characteristics of these forming surfaces, them can be considered asspecial cases of the sail surface of double curvature. In term of the actual situation, thispaper will focus on the springback of sail surface which is more universal. The formingmethod of force-displacement separated control (MPF-FD) is adopted and ANSYS isemployed for the numerical simulation. The impacts on the springback of the sheetthickness, forming force, radius, and parameter a in two different curvature directionsare obtained.The results show that the springbacks on two directions influence each other. Thespringback on the bigger radius direction is on the leading role, and will influence thaton the smaller direction. On the direction of the bigger radius, the springback isdecreased with the increase of sheet thickness, forming force and decrease of the radius.On the direction of the smaller radius, the springback is decreased with the decrease ofthe sheet thickness and the increase of the forming force, while the radius has a smallimpact on springback. On these two directions, the springback is first increased, andthen decreased with the increase of the parameter a. The geometric compensationmethod is proposed to solve the problem of the springback. Based on numericalsimulation platform of MPF-FD, the optimal displacement values of punch elements areobtained by analyzing the forming quality of the sail surfaces. The optimal value andtheoretical value of the displacement of punch elements are fitted, and obtained factorsthat are related to the slope and intercept of the fitting straight-line.Compared MPF-FD and multi-point die forming, the result comfirms that MPF-FDis better than multi-point die forming. The experiment shows that the problem of dentsis well solved under MPF-FD by improving the shape of the head of punch elements,and the direction of improvement of the mold is pointed out.