Study On Drawing Hole Technology Of Sheet Metal Forming

In order to answer the competition of energy shortage and environment pollution, light weight engineering will be the important direction of automotive industry in 21 century. Study and developed new techniques for improving the sheet metal forming property are the keys in realizing the automotive light weight. The practicality and effectual sheet metal forming technology should be satisfied with the qualifications as follows: 1) can be forming high strength aluminum alloy or dual phase steel; 2) labor productivity, production costs and mold working reliability must be identity or close agreement with the existent ripe sheet metal forming technique; 3) take full advantage of traditional production equipments; 4) might as well proceed processing at room temperature; 5) might adequately assurance the productive quality. Drawing hole forming technique is performed by processing some small and shallow blind holes in the flange surface where the flow resistance is extremely high, and depositing some lubricant in the blind hole, so the contacting area is decreased with the lubricate in the flange surface and the perfect sheet metal drawing ability is achieved. As a kind of simplicity and effectual measure in improving the properties of sheet meat forming and conform the above principles, it plays hopeful vital role in automobile light weight engineering. The main research contents and results embody as follows:According to the two typical drawing simulation of box part and cylindrical part, it is arrived a main method in improving sheet metal forming ability as follows: in the qualification of not initiating the wrinkle, brought more particle in fillet region into straight flange region, in the meantime cause the particle in the straight flange region run more distance towards the middle region which resistance is the minimal. A theoretical study of new technique is developed in sheet metal forming base on virtual power principle. The results indicate that decrease the equivalent stressσ, improve the lubricate state in contact surface, decrease the area, the normal contact stressσn and the equivalent strain velocityεin initial principal deformation region, adjust and optimize the particle cycle flow of work piece flange face will greatly increase the sheet metal draw ability in room temperature conditions. And drawing hole forming technology is araised based on the analysis above.The Kirchhoff hypotheses and Mindlin hypotheses in shell description is discussed and the measurement method and transition relation of strain, stress, strain rate and stress rate is expounded. The constitutive relation of finite deformation is discussed and constitutive equation matrices are founded based on Hill thickness anisotropy yield criteria. Based on updated Lagrange description, it is founded sheet dynamical analysis finite element formula, and stress amendment, single-point integration and hourglass control are discussed. Several key questions in simulation by DYNAFORM and LS-DYNA are expounded. At last drawing hole forming simulation of box part and cylinder part is proceeding and the results prove that the drawing hole forming technique could prominence increase sheet metal forming ability.Based on the discussion of elementary theory of artificial neural network and genetic algorithm, a sheet metal forming process parameters optimum design method is put forward by using finite element method, artificial neural network and genetic algorithm. Some technologies to solve the problems occurring in using are discussed. The method realized the nonlinear mapping relation and multiple objective syntheses optimization in sheet forming technology. Using the method, the technological parameters optimization of cylinder part and box part are realized, and the results proved that under the optimized hole density and blank holder force, the part could gotten preferable thickness distribution and lesser maximum deviation value than routine drawing.Experiments of drawing hole technique and routine drawing are performed, and the results indicated that in the cylinder part drawing the former could increase 45% drawing height than those of the routine drawing. In box part drawing hole forming it is also get more sound results. The experiment is the full proof verifying the viability of drawing hole technology. The drawing hole technique increases the lateral velocity in sheet transitional region, caused more particle in fillet region move to the straight flange region, thereby the resistance in fillet region is decreased and the forming limits is increased.In the platform of ANSYS software, parameterized finite element method is founded, and a direct chart for choosing the hole density is given out based on artificial neural network and genetic algorithm. The practicability of the chart and the validity of the compute model is verified by the simulation examples of panel part.