Phân tích bằng phương pháp phần tử hữu hạn (FEM) ảnh hưởng của trạng thái ứng suất đến quá trình biến dạng trong kỹ thuật ép đùn liên tục bằng ma sát qua kênh gấp khúc có tiết diện không đổi

NGHIEN Cflu - TRAO D6| PHAN TiCH BANG PHLCONG PHAP PHAN TLC H & U HAN (FEM) A N H HU-dNG CLIA TRANG THAI LfNG S U A T B i N QUA T R I N H BlfeN DANG TRONG KY THUAT EP DUN LIEN TUC BANG MA SAT QUA KENH GAP KHUC CO TI^T DIEN KHONG B | FINITE ELEMENT ANALYSIS OF STRESS EFFECT ON DEFORIVIATION IN CONTINUOUS FRICTIONAL ANGULAR EXTRUSION (CFAE) PROCESS Pham Quang', Nguyen Thi Hoang Canh', D i o Minh Ngirng', Nguyen Dang Khoa^ 'Vien Khoa hgc va Ky thuat Vat lieu, TrUdng Dai hoc Bach khoa Ha Ndi 'Khoa Cdng nghe Vat lieu, Trudng Dai hoc Bich khoa - Dai hgc Qudc gia Thinh phd Hd Chi Minh TOM TAT Dd sd diing phdn mem DEFORMTM 2D vdi thuat todn phdn td hdu han (Finite Element Method, FEM) de mo phong sd 2D qud trinh ep dim hen ttic bdng ma sdt kenh gdp khuc tiet dien khong doi (Continuous Frictional Angular Extrusion, CFAE) nham tao cdu true sieu cho vat lieu nhd hinh ;i hi Ti-Ni Phdn tich ket qud tinh todn dng sudt keo-nen theo chieu XvdY tdc dong len cdc phdn td di j qua goc kenh cho phep gidi thich cOchetrUOt vdxoay qua trinh bien dang deo ddn tdi cdu truchqt ^ gid tiidng bi keo ddi tdi 65% vd bi nen lai tdi 43% Qua cung ldm sdng to st^phdn bovd bi^n thien bien dang tren cdc phdn cua mdu ky thuat CFAE ABTRACT _ The DEFORMTM 2D commercial software package using finite element method (FEM) to simulate the continuous frictional angular pressing (CFAE) process was applied for bulk ultra-fine grained , (UFG) Nitinol alloy system (Ti-Ni) The sliding and rotation mechanisms of the plastic deformation leading to a 65% elongation and a 43% shrinkage of simulated grains were explained by analyzing calculated tensile and compression stresses acting on Nitinol workpiece in X and Y directions Thus the deformation distribution and evolution in CFAE-ed workpiece parts were also clarified Keywords: SPD, ECAP CFAE, FEM, UFG, Nitinol, Tini GlOl THIEU CHUNG true hinh thudng cd dang hat Idn, phan Idn l i bien hat djnh hudng gdc nhd, phuong , PhilOng phip bien dang deo m i n h Uet phip SPD cd can true dang hjt vdi bien hat (Severe Plastic Deformation, SPD) li qua trinh gdc Idn Cau true cua vat heu nhan duoc sau q u i e! t}o hinh kun loai vdi mdc bien dang Idn, i p ItJc trinh SPD cd dac diem nhU: i) kich thitdc tinh the dat Ien miu djng khdi d i n den thay doi cau true cua hat giam den cap dd nand; ii) mat lech tU S' vi md toin bd the tich cua mau d nhiet dd thap; iii) cac hat cd dinh hudng gdc Idn, nang thap vi lam nhd hat q u i trinh gia cdng lUOng v i tr?ng thii m i t cin bang cua bien hat cao Cac ky thuit bien dang manh nhu can v i keo cd [2] Cau triic dan den ting dang ki ben, thf lam hat d nhiet thap [ ], nhien cau deo, ehdng mii mdn v i tdc bien dang deo TAP CHl CO KHl VIET NAM • Sd (Thing nam 2012) ^ ^ NGHIEN C I J U - T R A D | Mdt eic phfldng phap SPD thdng dung nhat la ky thuat Ip kinh gap khue tiet di?n khdng ddi (Equal Channel Angular Pressing, ECAP) 13] Ky thuat niy dUa vio nguyen ly biln dang trUpt nhieu lan dan ldi kich thUdc hat khdi kim loai giam Qua trinh ep lap di lap lai nhieu lan gay bien dang deo Idn eua mau lim inh hUdng ldi die dicm eau true vi md cua vit li^u Khi dd cau true vi md eua mau hinh thanb cie hat dang hUdng vdi kich thfldc dfldi micrdmet Trong qui trinh ECAP, mau dflpe quay 90 o hoac 180 o theo Ip trinh ep A, B hay C gifla mdi lan Ip Cau true dii hinh thinh lan ep trflde dd se tao thinh cie hat ed kich tbflde nhd hpn de tao thinh eic hat sieu Qua trinh ehe tao tfldng ddi ddn gian va hi|u qui vdi nhieu loai vat li?u nhU kim loai, hpp kim hda bin phin tan, lien kim [4] va compozit nl'n kim loai [8] uous Frictional Angular Extrusion CFAE) [17] li ddi tflpng md phdng edng ngh? cdng trinh niy (hinh 1) Ky thuat CFAE la sfl ket hpp cua ECAP vdi qui trinh ep dun lien tuc vat li|u bang cich sfl dpng ma sil eua true cin qua Iflc ep len be mat mau Mdt vii nam trd lai day, Trfldng Dai hpc Bich khoa H i Ndi da nghien cflu ky thuat ECAP de che tao vat lieu (Ti vi Al) cd cau true silu chfldng trinh hpp tic nghiln cflu qudc te gifla TTNC Vat lieu hpc vdi Vien KIMS eua Hin Qudc (Korea Institute of Materials Science) vi d i cd nhflng ket qua cdng bd trin eic tap chi khoa hpc ehuyen nginh [11] Tuy nhien, ky thuat ECAP van edn ban che quy md phdng thi nghiem do: i) sfl dung nhilu thao tie thu cdng qui trinh van hanh cung nhfl vile di ehuyen phdi gifla mdi lin ep; ii) chieu dii phdi tfldng ddi ngan n i n chi flng dung cho cac chi tiet ed kich thfldc gidi han; iii) phan dau va cudi mau thfldng cd cau true khdng ddng nhat, xuat hien vet nflt rdng, phai cit bd lim ling phi mpt Iflpng Idn vit li|u Nhflng van de niy dan tdi gii thinh eua vat li?u sieu mjn che tao bang phfldng phip ECAP cao, khdng hieu qua Ke tfl gifla the ky 20, phfldng phap mo phdng sd tren cd sd thuat loan phin tfl hflu ban (Finite Element Method, FEM) la mdt nhflng each tiep can nghiln cflu dflpc i p dyng tren nhieu ITnh vUe khoa hpc vi cdng nghe Phfldng phip niy ed the md phdng tUPng ddi chinh xac cac q u i trinh vat ly xiy vat rin Cich tiep can niy d i dan tdi nhieu ket qui nghien cflu vi phit trien phUdng phap bien dang deo minh lilt tai nhieu phdng thi nghi|m tren the gidi, giiip cie n h i khoa hpc phin tich, d i n h gii mdt each tfldng minh qua trinh cd-nhi?t xay loan bp the tich cua khdi vit li|u cung nhfl qui trinh cdng nghi SPD De khae phue cic ban che tren, ky thuat ep liln tue tren be mat (Continuous Confined Strip Shearing, C2S2) 114] dang dflpc eic n h i khoa hpc tren the gidi tap trung nghiln cflu vi phat tril'n de cd the d i p flng dflpc quy md sin xuat Idn Ky thuat niy li sU ket hpp cua ECAP vdi qua trinh day ep lien tuc bang cic phUPng phap khic Trong do, ky thuat ep dun lien tuc bang ma sit (Contin- TAP CHI C O KHI VIET NAM Hinh - Sdsddd ky thudt Continuous Frictional Angular Extrusion (CFAE) Trdng cdng trinh da bfldc dau thiet lip md hinh cdng n g h | 2D q u i trinh ep dun lien tuc bing ma sit kenh gap khuc tiet dien khdng ddi (CFAE) Da flng dung phan mem DEFORM™ 2D [20] tren ca sd thuat toin phan tiS hflu ban (FEM) de md phdng qua trinh cdng nghe 2D CFAE Cae phan flng suit (theo phfldng X vi Y) tic dpng len mau qua gdc kinh ECAP dflpc p h i n tich Anh hfldng cua cic phan flng suit q u i trinh keo-nen cac phin to h^it gia tfldng da dflpc md hinh hda Nhd viy da lim sing td sfl phan bd cung nhfl bien thiln bi^n dang tren tflng phan v i tai cac diem da l\ia chon Sd (Thing nam 2012) NGHIEN cflu - TRAO 06l cua mau nham giai thich cP ehe lim nhd hat qua trinh CFAE M O H I N H H O A V A M O P H O N G SO QUA TRINH CFAE True can v i khudn dflpe Ifla ehpn vdi md hinh vit lieu tuyet doi cflng Khudn trin v i khudn dfldi tao thinh kinh vio v i kenh eua ky thuat ECAP vdi khe hd khdng ddi la 10 mm, cd gdc kenh chinh cD = 120" v i gde Iflpn Y = 0" True cin cd ban kinh R = 70 mm ddng vai trd ep tao ap Iflc day mau vio kinh ECAP Hinh l i md hinh ddng hpc cho ky thuat CFAE bai toin md phdng 2D dflpc thiet ke tren chfldng trinh DEFORM'" 2D Mau li md Hinh trinh cua true ein gdm hai giai hinh vat lieu bien dang deo ed dang thanh, kich doan: thfldc (255 X 10) mm dflpc chia Ifldi vudng vdi 2000 phan tfl - Giai doan 1: giai doan tinh tien de ep mau vdi tdc dp v = mm/s Hinh li md hinh hinh hpc cho ky thuat - Giai doan 2: giai doan xoay de day mau CFAE bai toan md phdng hai chieu (2D) dupc thiet ke trin chflpng trinh DEFORM'" vdi tdc dp V = 0,10472 rad/s (1 vdng/phut) Mau li dai vdi md hinh vit lieu bien dang Trong nghiln cflu niy, vat lieu dflde Ifla deo CO kich thfldc (10 x 255) mm va dfldc chia chon l i hpp kim Nitinol (51% Ti - 49%Ni) ed ludi vuong vdi 2000 phan tfl dang vdi mddun din hoi l i 83 GPa, he sd Poatxdng l i 0,33; ma sit gifla true cin vdi mau li 1, gifla mau vdi khudn l i 0,05 (gan nhfl ly tfldng) v i dflpe ep tai nhiet d6 25''C Dfldng cong flng suat-bien dang eua m i u trin dd thi eua hinh Cae thdng sd cua vat lieu dflpc trieh d i n sach "Smithells Metals Reference" 121] KET QUA VA THAO L U A N 3.1 Phan bo flng suat Hinh la ket q u i phan bd cua flng suat Hinh 2: Md hinh cdng nghe CFAE; 1- true cdn, 2- khudn tren, 3- khudn dUdi, 4- phdi ep kich thUdc phflpng X (a) va phfldng Y (b) tai dilm tren mau d gde kinh 120° nham giai thich qua (255x10) mm trinh biln dang khdng dn dinh v i thay doi hinh ding, kich thfldc cua cie md hinh phin to bii toin md phdng Thanh phan Ung suat theo phfldng Y l i keo ddn v i xap xi bang gidi han chay cua vat Heu Day ehinh li phan tao nen flng suit tiep tdi ban d l vat lieu cd the biln dang deo Kinh 3: Dd thi dng sudt - bien dang cda hdp kim Nitinol Hdp kim Nitinol cd cau true da tinh the gdm nhieu hat tinh the da canh, mdi hat diu cd mdt dinh hfldng rilng Dfldi tie dung cua Iflc ep dun tfl phia true ein, khdng phii tat ca eac hat deu cd the tham gia q u i trinh trfldt ma chi cd h a t ' ^ TAP CHf C O KHf VIET NAM V Sd (Thing nam 2012) NGHIEN CUfU TRAOD(!)l n i o CO mat trflpt vi phflpng trflpt thuan Ipi nhit (thfldng la mat trflpt vi phfldng trflpt tao vdi iflc mpt gde 45" th&o dd flng suit tilp Idn nhat) mdi cd the trflpt dflpc Dudi tic dpng cua Ung suit klo khdng diu cae phan id bj xoay di mdt gdc nhit dinh theo phfldng Y Su dinh hUdng khdc cua cae mat trflpt, phflpng trflpt so vdi phfldng tii eUa eae hat can ke dan den sU tic ddng tUdng hd gifla cdc hat O mpt phan trin be mil eua hat, Ung suit tde dpng tang len da hd trp thim cho sfl hinh thinh va ehuyen ddng cua lech Mat khic, flng lUe dd cd the tao thinh mpt ngau Iflc, lim quay hat Kit q u i li dinh hudng cua mil vi phfldng trflpt thay ddi ed Ipi cho qua trinh bien dang deo toin md phdng can xac djnh ti le keo-nen tren cac phin td hinh trdn nham thiy dd0c hinh thai bien dang di qua gdc kinh, tfl cd thi phin tich dflpc cd che lim nhd hat eCia vat lilu ky ihuilCFAE TU kit q u i md phdng, mau dflpc ep qua gde kinh cic phan td hinh trdn hi bien d^g, keo dii thinh cic hinh clip v i da xoay di mpt goc nhit dinh (hinh 5) Khi di qua gdc kinh 150", vung (1), cic phin td hinh trdn ban dau dflpc k^o dai vi xoay di mpt gdc, kit q u i cho thay cie phan td bi keo dii 21 %, nen 15% Tiep tue qua gdc kenh 120", vung (2), p h i n td biln dang manh hdn va bi keo dii tie dpng eua Ung suit theo phUdngY thinh eac hinh elip ddng true Nhu da trinh biy d trin, tai gdc kinh 120°, sU ehuyen hudng dot ngdt, thinh phan ilng suit theo phuong Y tic dpng lam cic mat tinh the bj xd lech, kit q u i li cac hat tinh the bi keo dii (bien dang) theo phUdng trUdt tdi 65% Tren hinh 4a Ung suat theo phfldng X bao gom ca hai thinh phin keo (= 100 MPa) v i nen (= 600 MPa) Thinh phan flng suit kid khdng dang ke dan id! eic p h i n td bi nen lai theo phfldng X Nhfl viy di qua kenh 120", phin td bi keo dai tdi 65%vibi nen lai tdi 43% (b| \Jng suit Iheo phaong Hinh - Phan hd vd hien thien dng sudt qua diem tai gdc kenh theo phUdng X (a) vd phUdng Y (b) Ngoii sfl quay eua hat dan den vile hinh to chUe textua, phfldng mang cua kim loai cd xu hudng song song vdi de tao eac hat ddng true Kha nang biln dang deo tang lin lam vit lieu tang dp deo sU khae biet theo phfldng mang eua hat giim ,\\ Wi ^ % /^^ VliV«r Hinh - Tile keo-nen theo cdc chieu mdu di qua cdc gdc kenh sau mgt lan ep 3.2 Cd che biln dang CFAE De lam rd them tic dpng eua cac thinh phan flng suat keo-nen ddi vdi cd ehe bien dang cung nhfl sfl thay ddi cau true v i kich thfldc hat qua trinh CFAE, cic hat ban dau eua vat li|u dflpc gia thiet li cae p h i n td hinh trdn Trong bai TAP CHf C O KHi VIET NAM V Qua trinh bien dang l i m eac hat thay doi hinh dang, kich thfldc va p h i vd cau triic ban dau nen td chflc hat nhan dflpe thudng co to chiJc sdi sau bien d^ng manh (nhfl trdng ky thu^t ECAP) Qua trinh ep khdi vat lieu nhilu lanvcli eae 10 trinh khic nhau, vdi mflc bidn dang rSt Idn Sd (Thing nam 2012) NGHIEN Cflu - TRAO D O I se lam cho to ehUe sdi n i y de xay cd ehe song tinh, gop phan lim tang sd lUpng hat, nghia la giam kieh thUdc hat ban dau Day ehinh l i ed sd ciaa eP ehe tao eic hat cd eau true silu ky thuat ECAP 3.3 Phin bd va bien thiln bien dang Hinh 6(a,b) l i kit q u i md phdng bil'n dang eua mau tai thdi dil'm eudi eung eua mdt lan ep vdi toe dp quay cua true ein khdng ddi v = 0,10472 (rad/s) TU kit qua nhan thay cd ba vung mau di qua lim tang bien d^ng: vi biSn dang (= 0,13) true cin ep Ien miu Ket q u i hien thi mau dd tuong dng phan bd bien dang Idn nhat cho thiy ket qua md phdng hoin toin phii hop vdi ket q u i tinh toan Til ket qua md phdng nhin thiy bien dang tai phan phia tren cua mau Idn hon phan phia diy mau, sU sai khic niy ngoii yeu td ma sit gid miu va thinh khudn thi cung cd i n h hudng cua gdc kenh va gdc luon Y [231 Effective SIrain, imWmm Strain inmitant Vung 1: vung true cin Ip xudng m i u de tao ma sit gay bien dang d i n hdi Vung II: vung gdc kenh thfl nhi't vdi O = 150° Vung III: vung gdc kenh thfl hai vdi O = 120" Kit qui md phdng cdn cho thay mau bat dau bien dang tai vung thfl nhat (1), tang thim biln dang qua vung gdc kinh 150" (II) vi tiep tue bien dang manh di qua gde kenh Hinh - Phdn bd vd bien thien bien dang cua mdu 120o (III) Bien dang eua mau dat dflpc sau sau mpt lan ep CFAE di qua goc kenh niy l i tdng hpp bien dang cua e i ba vung trin Gia tri bien dang dat cao nhat l i = Kit qua md phdng edn cho thay bien dang 1,13 (113%) (tren hinh 6a bieu thi bang vung miu cua mau dat dUde tUdng ddi ddng deu dpc theo do), kit qua niy hoin toin phu thudc vio die tinh chilu dii cua miu, bien dang cd gia tri tfl 0,8 den hinh hpe eua khuon chpn ban dau 1,15 trU phan phia dau cua miu Do vung dau mau ed chfla mat tfl vi khdng di qua ba vung Biln dang tinh dflpc bang each thay eac bien dang da n l u trin, nin biln dang dat dflde gia tri gdc kenh va gdc Iflpn v i sd lan Ip N = vio khdng ddng deu va dat gii tri thap nhat = 0,15 phfldng trinh dac trflng cua ky thuit ECAP [3]: Hinh 6b la thi bil'u dien qua trinh bien c,=^[2cot(t-^)-Vcos,c{t-^)] (3) thien bien dang cua mau Nitinol khio sat tai diem doe theo chilu dii cua mau Nhfl da bilt, cd ba giai doan (1,11 vi III) lim tang bien dang eua Cng vdi gdc kenh ® = 150°, gdc lUdn Y = mau, dieu niy dfldc the hiln ro tren dd thi vdi ba Oo se tinh duoc ket qua bien dang e V 0,3 (30%) mflc flng vdi ba giai doan qua trinh CFAE Vdi gdc kenh