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-V NGHIEN ClJfU-TRAODCl ; '^ RESEARCH ON THE HYDROSTATIC FORMING TO PRODUCE COMPLEX SHEET PARTS IN CARS NGHIEN c u r CONG NGHE DAP THUY TINH DE TAO HINH CHI TIET PHLTC TAP TRONG XE OTO ^ , ^ Dinh Van DuyS Tran Anh Quan' NguVen Thi T h u \ Nguyen Dac TrungS Le Trung Kien^ ' Industrial Machinery and Instruments Holding (IMI Holding) ^Hanoi University of Science and Technology, Department of Metal forming ABSTRACT f/^^ in the automobile manifacturing industry, most of sheet parts in the body of cars are f' complex Moreover, the preciseland qualitv of their shape, geometry and durability have to be warranted during manufacturing Therefore, it is difficult to deform them by common methods, such as forming with solid punch and dia pr with rubber punch or with rubber die One of the most advance methods, which drew the'interest of researchers recently and was applied to produce the complex sheet parts, is the hydrostatic forming By using the high pressure of liquid, hydrostatic forming makes the part deform easier and increase the quality of its surface However, in Vietnam, this method is smlllnew, so it hceven't been applied widely yet The authors built the model for center pillar - a part to link two dqors in a car- and researched the influence of parameters of hydrostatic fprming on the quality of this part This paper shows the simulation result of this research with Dpnaforrn an^ setting empirical model Keywords: Hydrostatic forming, sheet metpl forming, ^T6MTAT \y hydo-forming I, Trong cdng nghiep sdn xudt oto, hdu f^et cdc chi tiit cua vo xe deu co dgng tdm phuc tgp vd cdn dugc ddm bdo ve hinh ddng, cMt lugng vd dp bin qud trinh che tgo Do do, viec tgo hinh chimg khd kho khdn doi v&i/dcpfiuang phdp thong thu&ng nhu sic dung chdy cimg, coi cung hay su dung cdc loai chdy hggac&i bang cao su Mpt nhicng phuang phdp tiin tien dang dugc quan tdm nghien cicu ya miugc su dung de che tgo chi tiet vo mong phuc tgp Id cong nghi dap thuy tinh V&i viec siefiunsap sudt chdt long cao, dap thuy tinh giup phoi de biin dgng vd tdng chdt lugng bi mat sdn phdm Tuy nhien, a Viet Nam, phuang phdp ndy cdn khd m&i vd chua dugc ung dung rpng rfii Nmm tdc gid dd xdy dung mo hinh cho chi tiit ndi cdnh cua to vd tiin hdnh nghien ciru dnhmmng cua cdc thong sd cong nghe dap thiiy tinh t&i chdt lugng cua sdn phdm Bdi bdo trinb^boy ket qud nghien cuu bdng mo phong sd v&i phdn mim Dynaform vd mo hinh hi thong thicc hmiim cong nghe ndy Tir khda: Dap thuy tinh, tgo hinh thuy luc, tgo hinh vdt lieu tdm i / ISSN 0866 - 7056 TAP CHi CO KHf VIET NAM, S6 1+2 nam 2015 www.cokhivietnam.vn l^ ^ NGHIEN cufu-TRAOD6| INTRODUCTION Today, in the developed countries in the world, hydroforming in general has been applied to the fabrication parts of cars because of its superiority Fig L: M-i' O^ Fig.l Industrial examples of tube and shell hydroforming- (a) - engine cradle, (b), (c) - Pontiac Solstice and parts made by hydroforming [3], (d) - exhaust system of Kawasaki [5] Compared with conventional press, hydraulic press technology has the preponderance in forming the thin shell detailed By this method, the quality of products is more advanced, the ability to form the intricate parts is also higher Therefore, it is usefiil in fabricating thin shells in general detail Fig.2 Comparison of exhaust systems produced by conventional methods (a) and by hydroforming (b) [5] [7] Depending on the shape of the product and the original embryo selection, we divided into different forming methods For tubular products, hydrostatic forming is the optimal choice to create the complex shape Fig la, Id For product sheets, we can use the method of hydrostatic forming or hydroforming to form the parts Hydrostatic forming, among many advanced methods applied to research and produce these parts, uses high pressure liquid to act directly on the sheet metal and presses the blank following the shape of die Meanwhile, the hydroforming also uses high pressure liquid which are created by combining the movement of machines, and presses the blank following the shape of punch ^ ISSN 0866 - 7056 TAP CHI CO KHi VIET NAM S6 +2 nam 2015 www.cokhivietnam.vn NGHIEN CUTU-TRAO Ddi In Vietnam, the study of this type of technology is still lunited, especially for hydrostatic stampmg from sheet metal Therefore, authors surveyed, research to bring this technology into car industrial applications in the domestic - a field still limited development '"' ^ T' X ""•••**"*• ^'iy ^„ •-"A^i-^^A Fig Diagram of the hydrostatic forming for sheet metal [7] [6] THEORETICAL FOUNDATIONS OF HYDROSTATIC FORMING While normal drawing uses both the solid punch and solid die, the hydrostatic formmg uses high pressure fluid to deform the part following die's shape It results in differences in sh-ess - strain behavior of these methods Stress state in normal forming usually divides into zones: flange, body and base of products, especially, in the body zone, it is only single stress state (Fig.4a) Meanwhile stress state in the hydrostatic forming is virtually flat stress state '"**