Multi-objective Optimization Of Structural Parameters For Rotary Extrusion Of High Ribs In The Inner Ring Of Magnesium Alloy Cylindrical Parts

With the development of science and technology,the requirements of weapons and equipment,aerospace,aircraft,satellite and other industries for the manufacture of spare parts are also increasing day by day.The lightweight of high-end equipment with high-quality production requirements has gradually become the mainstream of the development of the times.Straight-walled cylindrical parts with inner ring ribs,as a common shell parts,are widely used in the field of high-end equipment.The development of this kind of parts needs to meet the requirements of light weight and high performance.As a kind of high-quality light alloy,magnesium alloy has attracted much attention from scholars engaged in metal performance research and engineers in the metal forming industry.however,the traditional manufacture of magnesium alloy ribbed straight tube wall parts has some disadvantages,such as high scrap rate,low production efficiency,low economic effect,low service life and so on.aiming at the problems of low rib strength and too much processing waste in the manufacture of ribbed cylindrical parts,Later,a new rotary extrusion process was proposed to manufacture this kind of cylindrical parts with inner ring ribs.The rotary extrusion process has remarkable advantages such as reducing the forming load,improving the formability and improving the properties of the inner ring ribs.At present,the rotary extrusion process is still in the stage of development because of its special die loading mode.The movement state of the three-way linkage die leads to a complex metal flow trend on the blank cylinder wall,so the inner ring ribs of the cylindrical parts formed by the rotary extrusion process are also subject to many restrictions.For example,the radial height of the formed inner ring rib is insufficient;The shear force caused by the interaction between the die and the rotating cylinder blank makesthe damage value too large,and the local stress concentration leads to defects such as rib cracking.There is no doubt that the immature rotary extrusion process has great development potential and economic benefits,so it is worthy of in-depth study.A new type of split punch with deep inner groove and double working belt is put forward on the basis of the existing rotary extrusion process and the basic principle of metal plastic forming.The structure of the new split punch is simplified,and the stress state on the working belt of the split punch in rotary extrusion is analyzed,and the complex stress state on the working belt is divided into radial,tangential and axial analysis.It lays a foundation for the strength check of the split punch of similar structures.Based on the analysis of the law of metal flow in the process of rotating extrusion inner ring rib,the transfer process of metal from the inner wall of cylindrical blank to the inner groove of split punch is described.the possible convection folding phenomenon of metal in the inner groove of split punch is solved by adding stagnant zone on the metal accumulation groove of split punch.According to the law of metal flow,the split punch structure parameters which have the most significant effect on the inner ring rib forming of cylindrical parts are selected from many factors affecting the forming of inner ring ribs of cylindrical parts.The central compound experiment method is selected to design the experiment in line with the actual operation,and a total of 30 groups of experiments with four factors,five levels and three optimization objectives are designed for computer simulation,so as to obtain the influence of different combinations of punch structure parameters on the optimization goal.The rapid modeling is carried out by using the powerful drawing format recognition ability of UG software,and the transformed 3D modeling is imported into DEFORM-3D software for simulation on the premise of considering the uneven deformation of the inner ring ribs in the cylindrical parts.The post-processing results are analyzed and the effective data of the three optimization objectives in the simulation results are extracted for integration.Using Design-Expert software to select appropriate regression model to analyze the integrated data in the simulation results,establish reliable mathematical model and response surface model,qualitatively analyze the contour map and response surface map describing the relationship between optimization variables andoptimization objectives,and further explain the influence of optimization parameters on optimization objectives.Finally,multi-objective optimization is carried out to obtain the best combination of structural parameters with comprehensive forming effect.A new type of split punch with the best combination of structural parameters is applied to the trial production of stiffened cylindrical parts,and the cylindrical extruded parts with qualified dimensions and properties are produced,which can be used as a reference for the production and optimization of similar ribbed cylindrical parts with rotary extrusion process.