Study On Plastic Forming Rules Of Magnesium Alloy Square Box

Magnesium alloys with the characteristics of light weight, high strength, nottoo expensive, favorable environmental and recycling are increasingly becomingthe ideal materials for modern industrial products. They have been applied widelyfor light structural and functional parts, especially in the automotive, aerospace andelectronic industries. And because of lower density, better collision safetyproperty and electromagnetic interference shielding capability, magnesium alloysare available for producing some structural parts such as the coverings of mobiletelephones, notebook computers and portable Mini-Disks (MD). Presently, Most ofmagnesium alloys parts are processed by die casting. But die casting products haveholes and bubbles. So the mechanical properties of die casing parts often do notmeet the strength requirements of force-supported parts. And this process is notideal in making thin-walled Mg structures because of excessive amount of wastematerials. Although sheet metal forming processes (such as thermal drawingprocess) are developed to make thin-walled parts with good mechanical propertyand surface quality to avoid the defects above, because of its hexagonalclosed-packed (HCP) crystal structure, in which only the basal plane can move, themagnesium alloy shows low ductility at room temperature. Presently, some studiesfound that formability of magnesium alloys can be effectively improved byenhancing forming temperature, and deformation behavior of thermal magnesiumalloys was studied in the present study. But the systemic study about sheet metalthermal drawing process is few.In magnesium alloys sheet thermal drawing process, square box workpiecehas some few representative and difficulty. The finite element simulations of squarebox drawing of AZ31B sheet at various forming temperatures are performed in thispaper to investigate the effects of the process parameters on the formability ofsquare box drawing. Drawing equipment is designed according to the simulationresults. These provide available theory basis and technique approach for furtherstudy.This dissertation research content includes:1.Theory and key technology of numerical simulation of magnesium alloyssheet thermal drawing process are systematically summarized. Thethermal-elastic-plastic constitutive model in magnesium alloys sheet metal thermaldrawing process is established, and the heat transfer of thermal-mechanicalcoupling is calculated. The general finite element formulation for non-linearthermal-mechanical coupling is provided based on the virtual rate principle. Inaddition, the static implicit algorithm is discussed.2.The noticeable problems such as geometry model, meshing, material model,contact, friction and boundary conditions are brought forward, which are relating tomagnesium alloys sheet thermal drawing process.3. The author uses MSC.Marc software to simulate the magnesium alloyssheet thermal drawing process. The rules of change of stress and temperature fieldduring forming are analyzed to forecast the disfigurement of the square box. Thesimulation results show that the locations at which stress is strongest during theinitial stage of deformation are corners of punch and die, which are maindeformation areas. The flange areas also become main deformation areas duringfurther deformation.4. The finite element analysis is performed to investigate the effects of theprocess parameters on the forming of square box drawing including formingtemperature, punch temperature, blinder force, friction coefficient and drawingvelocity to elicit the affecting rules of different parameters on the square boxquality .The author ascertains the best process parameters to improve formability ofsquare box drawing:(1) In the simulation, the formability of magnesium alloys square boxenhances as rise of temperature. The magnesium alloy shows an excellent...