Numerical Simulation Of Multi-steps Forming And Sectional Multi-point Forming For Sphere

Multi-point forming (MPF) is the technology which forms three-dimensionalsurface part by the envelope surface of punches, this technology bases onnumerical information of part, driving by three-dimensional CAD model of part. InMPF, the solid die is replaced by flexible MPF die composed by a series of discreteelement (or punches). In conventional stamp forming, the part is formed by thesolid die surface, in MPF, the part is forming by the envelope surface of punches.The height of every punch is controlled by the computer, the forming surface isconstructed through adjusting the displacement of element according to the shapeof part, so that MPF can realize the fast and flexible forming. MPF is a flexiblemanufacturing technology for three-dimensional sheet metal forming, used in manykinds of 3-D surface part. At present, the MPF press can process a mass ofcomplicated shape and smooth-faced parts. The technology has been applied tomanufacture streamline head of the high speed train, outer board of ship andtitanium alloy cranial prosthesis.In practice, the deforming of part exceeds the maximum of the material in onestep forming, the part can't be formed in one step forming, the matter can beresolved with the multi-steps forming. In conventional forming, the multi-stepsforming need several dies, so that the cost of manufacture is increased, the periodof manufacture is prolonged. As a flexible technology, the MPF construct theforming surface quickly according to the shape of part, consequently realize themulti-steps forming in less cost and shorter period.The essential of multi-steps forming is that the large deforming is divided intoseveral small deforming, the part is formed in several steps. With multi-stepsforming, the small deforming is accumulated to the large deforming. Thedeforming path can be changed through designing the forming surface in every step,the sheet metal is formed in the mo te path, so that the defects can berestrained or even eliminated, the pacity of the sheet metal is alsoadvanced.the smf every part ofworkMulti-steps of multi-point forming and sectional multi-point forming belongerical simulation.Theof material, element type, boundary condition, the transfer ofinformation about deformation of part in different step, the disposal of dieinterinance in advancing theform e forming quality of part.Mult ad been simulated with the finite elementnum(1)The cushion is the effective method to restrain the dimples in multi-pointhion is, themore evident restraining effect is, and the forming capability of sheet metal isa will be affected when thethickness of cushion is too big. If the precision is affected with the thickness ofshion, the shape of forming surface should be modified.(2)The smaller increment is , the better forming capability is. With the smallcrement, the deforming is well-proportioned. the sheet metal is harded ande yield limit is heightened after every step forming, the forming capability ofthe whole sheet metal is enhanced.(3)The thickness of sheet metal is important factor for the sheet metal choosingthe deforming path. If adopting the same material to forming the same part,with the sheet metal thickness increasing, the forming steps decreasing and theincrement in every forming step increasing. The reason is that the ability ofsheet metal resisting instability is advanced when the thickness increasing.(4)Different material has different forming capability, requiring differentst appropriaforming caSectional forming starts a new way for the large-scale sheet metal formed inall equipment. The tonnage of equipment is dwindled with this technology,saving the cost of developing new equipment. Because the workpiece isn'tseparated, the property of sheet metal is guaranteed. There are strict requirementson the equipment in sectional forming, owing to the different shape opiece, the equipment must be flexible. Multi-point forming is so flexible that itsuit to sectional forming。The research on sectional multi-point forming isimportant to exert potential of multi-point forming equipment.to multiple-steps forming, the forming is more complex than one-step forming, theresearch on multiple-steps forming adopts the finite element numkey of the simulation on multiple-steps forming includes the techniques suchas the yield ruleference.Multi-steps of multi-point forming has predoming capability of sheet metal and improving thi-steps of multi-point forming herical simulation, the results gained are:forming. In multi-steps of multi-point forming, the thicker the cuslso advanced. It notices that the forming precisioncuinthdeforming path. The material has better forming capability with smaller ratio ofyield strength to tensile strength. When ming the same shape of part, thesheet metal with smaller ratio o ngth to tensile strength has fewerforming steps and bigger increment in every forming step.Sectional multi-point forming is a flexible technology, it has evidentquipment can formlarge-scale sheet metal when adopting sectional multi-point forming. This forminging, it is simulated with finite element numericalsimulation. The main problem in sectional forming is local complex plastic formingclusions gained are:(1)Sectional for ming, it is difficult job tois common phenomenon that only exists inforf yield strepredominance in processing large-scale sheet metal. Small ebelongs to multiple-steps formof the transition area. The conming belongs to multiple-steps forsimulate sectional forming, because it is the numerical simulation processincluding sheet metal forming simulation, springback simulation andmultiple-steps forming simulation. In this paper, finite elementsoftware—ABAQUS is introduced to simulated the sectional multi-pointforming. The numerical simulation is help to explore the rule of the sectionalmulti-point forming.(2)The key of sectional multi-point forming is harmonizing designing thetransition area. The forming surface of transition area is designed byNURBS(Non-uniform Rational B-surface ) through software CATIA, the wavesurface defect is restrained with the harmonizing designing the forming surfaceof transition area, the forming quality has been advanced.(3)The local complex plastic formingsectional forming, there are factors effect the local complex plastic formingsuch as the thickness of sheet metal, the material of sheet metal, etc. Thetransition area of thin sheet metal is smoother than that of thick sheet metal,and the transfer of the force is more well-proportioned;when the material hassmall yield strength, the transition area is long, when the yield strength ofmaterial is big, the transition area is short.