Research On The Material Flow Law Of Magnesium Alloy Cylindrical Parts With Inner Ribs During Hot Power Spinning

Lightweight is an important direction for the development of products in the fields of aerospace,weaponry,and transportation.It not only puts forward requirements for lowering the product itself,but also requires higher and higher component performance and precision.The combination of lightweight materials such as magnesium alloys and lightweight structures such as thin walls and inner ribs is an important way to achieve lightweight components.Magnesium alloys exhibit poor ductility and show difficult to deform at room temperature.Therefor its plastic deformation is mainly carried out under heating.Magnesium alloys have high temperature sensitivity and are prone to various defects during the spinning forming process,which makes the forming quality more difficult to control.Furthermore,in addition to the axial and radial flow of the material,a large tangential flow occurs,which makes the flow of the material extremely complicated during the forming process.Therefore,investigation on the material flow behaviour of the hot power spinning forming of magnesium alloy cylindrical parts with inner ribs has important theoretical guidance and production practical significance,not only in controlling the occurrence of related defects but also in obtaining good quality cylindrical parts with inner ribs.In this paper,magnesium alloy cylindrical parts with inner ribs were used as the research object.Based on COMSOL software,an electromagnetic induction heating model of pronation blank was established,to reveal the influence of induction heating parameters on the temperature field distribution of blank,spinning experiments were further carried out to validate the reliability of the FE model.The results show that the temperature field of the pronation blank presents the overall characteristics of high outer surface temperature,low inner surface temperature,and large outer surface magnetic flux density;The maximum core temperature difference of the blank shows a gradually increasing trend with the increase of the current frequency,current intensity and the number of turns for the coil,but shows a gradually decreasing trend with the increase of the distance between the coil and the blank;Compared with the current intensity,the current frequency has a more significant influence on the temperature field distribution of the blank;The optimal combination of induction heating parameters is:I=135A,f=10k Hz,T=300?,d=2mm.Based on ABAQUS,a thermo-mechanical coupling model of the hot power spinning forming of magnesium alloy with inner ribs was established,to analyze the multi-physical field in the forming process.The material deformation characteristics and flow behaviour of ribs and walls were explored,and the influence of material flow on the forming process was studied.The results show that the heating effect caused by friction and deformation is stronger than the cooling effect caused by heat exchange.The wall deformation is greater than the ribs,and the material in the wall is both elongated in the axial and tangential directions,and compressed in the radial direction;The deformation law of the material in the outside of the rib is consistent with material in the wall,and the inner material stretches in the radial and axial directions,but compresses in the tangential direction;Material deformation presents characteristics such as periodicity,inhomogeneity and asymmetry;The filling of the inner ribs mainly relies on the inflow of the inner layer material of the blank in the radial direction.The tendency of the inner layer material to flow in the radial direction is gradually increased from the wall to the rib,and the trend of tangential flow is gradually slowed from the wall to the rib,and diversion occurs at both sides of the inner rib.The material flow is likely to cause defects such as inhomogeneity of inner ribs and sunken of ribs back.Based on the flow behviour of the material,the influence of the structural parameters of the inner ribs(the shape of the inner ribs,the number of inner ribs)and thinning ratio of wall thickness on the material filling was studied.The results show that the trapezoidal inner ribs are more conducive to the radial flow of materials to form inner ribs than rectangular inner ribs;The growth in the number of inner ribs shortens the distance for material flow to fill the rib groove,which is beneficial to the radial filling of the material to form the inner ribs;As the thinning ratio of wall thickness increases,the ratio of the average height of the ribs to the reduction decreases,which means increasing the inner ribs of the same height requires more filling material.Based on the orthogonal test of hot spinning,range analysis and gray correlation analysis method were used to reveal the influence of process parameters on the straightness,roundness,sunken ratio of ribs back,saturation of inner ribs and inhomogeneity of inner ribs.The optimal process parameter combination was obtained.The results indicate that the primary and secondary order of the comprehensive influence of various process parameters on the forming quality of spinning parts is:number of inner ribs>wall thickness>thinning ratio>forming temperature>feed rate,and the optimal combination of process parameters is:N=12,t₀=8mm,?_t=70%,f=0.4mm/r,T=350?.