Calculation of kinematic schemes taking into account tension during stretch-forming of thin-walled structures

One of the methods for producing single and double curvature skin parts is the stretch-forming process. Modern stretching presses have numerical control. To set the control program of the stretching press, it is necessary to construct an involute of the clamping jaws motion. As is known, for a tight fit of the workpiece on the punch during stretch-forming, it is necessary to set the tension. The distribution of tensile forces in the workpiece on the punch, taking into account friction, is uneven and can lead to unequal springback for different parts of the workpiece. The article presents a method for calculating the involute or trajectory of the T-600 press control elements motion of during sheet stretch-forming by simulating the workpiece deformation process in a CAE system. Tension is taken into account when simulating the sheet stretch-forming process. An analysis of the workpiece adjoining area dependence to the punch depending on the magnitude of the tension force is presented. It is proposed to take into account tension in combinations of boundary conditions when modeling the process of the workpiece deformation for calculating the trajectories of the press control elements movement for various stretch-forming schemes. The found trajectories are compared with the trajectories calculated geometrically. The proposed method for calculating deformation trajectories allows taking into account geometric and physical nonlinearity, correctly determining the level of deformations, stresses and choosing the optimal option.
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