NGHIEN Cl/U • TRAO OOI tfNG XU* CO HOC TAI MOT DIEM BAT KY CUA TAM KHI TAO HINH BANG SPIF Ths Nguyin Thanh Nam', TS NguySn Thidn Binh' Dodn Ihanh Phong', Nguyin T^n Hung', U Khdnh Diln^ 'Phdng thi nghiem Dieu khiln sd vd Ky thudt h$ thdng Trfldng Dai hpc Bach khoa TR Hd Chi Minh ^Bd mdn Thilt kl Mdy, Khoa Cd khi, Trfldng Dai hpc Bdeh khoa TR Hd Chi Minh T6M TAT Chuyen vi, bien dang va iing sudt ludn Id cdc yen to cdn bdn vd thiet yeu ly thuyet bien dang deo cdn dUdc khdo sdt trUdc tien de tii diing ldm cd sd tinh todn khd ndng bien dang cua vdt lieu qua tieu chudn chdy cua Von Mises hay Tresca Ddy cQng Id cd sd de tinh todn lUc, moment vd cdng sudt tao hinh tao hinh tdm bdng bien dang cue bo lien tuc (SPIF: Single Point Incremental Forming) Muc tieu cua bdi viet Id thiet lap cdng thiic tinh iing sudt tai mot diem bdt ky vung tao hinh cda tdm dUa tren cd sd ly thuyet cd hgc ddn thudn ket hdp vdi thUc nghiem Bdi bdo ciing giup xdc dinh dt/dcgidi han tao hinh SPIF phii hdp vdi gid tri thiic nghiem cua cdc nghien citu tnidc ddy Tii khoa: cong nghe bien dang cue bo lien tuc, ddn hoi deo, kim logi tdm, bien dgng cd hoc ABSTRACT Displacements, deformations and stresses are always basic and essential elements in theory of plasticity They need to be studied and calculated when researching the ability ofplastic deformation criteria of Von Mises and Tressca These above elements are used as the base of the problems of forces, moments and powers in forming sheet by SPIF (Single Point Incremental Forming) Hence the purpose of this paper is to calculate the formula of stresses at a random point in zone of deformation The paper defines also the limits of forming in SPIF that are suitable with the empirical results of recent researches Key words: single point incremental forming, elasto-plastic, sheet metal forming, mechanical deformation theory TAP CHf CO KHI V I £ T NAM • • • Sd 03 (Thdng nam a m ' ;!' I II , NGHIEN cufu - TRAO D(!)l BIEN DANG TUONG DOI VA Ul^G SUAT PHAP TAI DIEM M BAT KY TRONG VtJNG TIEP XUC 1.1 Theo phfldng chu vi p vudng gdc vdi bien dang dung cu tao hinh Tren hinh dilm M bat ky (gdc COM=(p) Theo phdn tich bien dang [ ] thi mdt tren ehu vi vdng trdn tdm H, bdn kinh r=HM, dilm bat ky M ban dau nam d tilt dien trung hda dfldi tde dung eua dung cu tao hinh vdng bi gifla tam phang se di ehuyin den M' cung bien dang thdnh vdng tdm H', bdn kinh r'=H'M' nam gifla mat cong tiet dien trung hda tam bi biln dang ddng thdi theo phfldng M vd Xet tam giac vudng MHO vd tam gide M' nam tren tia OM' hdp vdi true OZ eua dung vudng M'H'O: eu tao hinh gdc COM=9 He tpa dp OXYZ ddt tai Ban kinh ehfla bien dang: tdm O eua dung cu tao hinh, true Y vudng gdc vdi mat phang hinh ve, gpi t Id be ddy ban dau eua MH r= OH.tg(p = (— -H ^ - h).tg(p tam va t Id be day tam tai M' Chuyin vi eua M theo phfldng vudng gdc nhfl sd tren hinh Chu vi vdng (H,r=MH) hay chilu ddi ban dau theo phfldng p: ^ ^D r ,, D ^ D+r.-2/i Bdn kinh r'=M'H sau biln dang: D + t