Research On Fatigue Life And Optimization Of Die Structure Based On The Whole Process Of Forward Extrusion

As an advanced production technology widely used in industrial production, cold extrusion has the characters such as high precision, high efficiency, high quality, low consumption and so on.Because of hunge pressure in extrusion, the fatigue life of die is short, so the reasonable die structure is especially important. Therefore, research on the cold extrusion process and the optimization of the process parameters have the vital significance.According to the technological process of solid forward extrusion, the whole technological process including interference assemble of die, placing workpiece, extrusion, unloading, ejection is reproduced by the simulation. Based on the stress, strain and temperature distribution in the process of extrusion, a new technology project is used sectional die-sleeve to offer variable shrink range as well as the specific technology implementation method, and used the simulation as the numerical validation. Subsequently, according to the real process parameters of a Shanghai automotive fasteners company, the characters of different structures of long concave die were compared through the whole process flow simulation analysis, and the final die structure is determined. By writing python file of parameterized model, the key process parameters(the chamfering and interference quantity), and the process control parameters(friction coefficient) of double prestressed die structure in solid forward extrusion of bars were optimized by using the genetic algorithm II.Design of experiment(DOE), Optimal Latin hypercube sampling method is used to sample the sample space and constructed the response surface model on the basis of the sampling results, the complex and time consuming simulation program is replaced by the response surface model during optimization. This method can greatly save computation time.Finally, the result of the genetic algorithm II is compared with the optimization result to verify the feasibility of this method. This method provides the possibility for the actual engineering application.A new Optimal Latin hypercube sampling method was proposed and a series of improvement was carried on error analysis as well as optimization. Finally, the feasibility of this method was verified by the better solution.FE-SAFE–ISIGHT-ABAQUS optimization simulation platform is built in this paper. The fatigue life of Pareto solutions of genetic algorithm II is calculated on the basis of the platform to verify the correctness of the optimization results. Finally, how to increase the fatigue life of die has carried on the detailed analysis and discussion. The platform can be further applied in the optimization of the die structure and fatigue life analysis.