Journal of Science and Technology.-N. 166(2-2015) - Military University of Science and Technology___—
ANH HlTOfNG CUA THAM SO CONG NGHE DEN K i C H THU*6C DirCfNG DON TAO HINH BANG TIA LASER
Doan Tdt Khoa, H6 Viet Hdi*
Bai bao trinh bay viec xSy dirng mo hinh toan hpc vS dp rong, do cao dirong don \h tien hanh thirc nghiem tim ra quy luat Mi huang cua cac tham s6 cong nghe den kich thudrc dirong don. K^t qua cho thSy miic dp anh huong cua cac tham s6 cong nghe d^n kich thu6c duong don nhu: van t6c qu6t chum laser; c6ng suit laser; khoang each tuang d6i giiia vj tri hoi tu dong bot va vj tri vimg nong chay; luong dp bot. Tir do, c6 thi xac dinh tham so cong nghe tim ra bo tham s6 cong nghe hop ly lam co so dl tao hinh san phdm.
Tir khoa: Cong nghe Igo hinh bSng tia laser, vung nong chdy, duang dan, tham so cong nghe.
1. Dat van de
Cong nghe chi tao san phim sir dung phuang phap thieu kit true tidp b6t kim loai bing tia laser (Laser Direct Metal Forming - LDMF) la mgt trong nhiing cong nghe tao hinh san phim kim loai hien dai hien nay. Cong nghe nay bit dau phat triin tir nhiing nam 90 cua thi ky XIX, la su tich hgp cua cong nghe laser, cong nghe dieu khiln s6 (CNC), cong nghe may tinh, cong ngh§ vat lieu... sir dung ngu6n nang lugng laser thieu kit hot kim loai di chi tao san pham theo nguyen ly tao hinh timg lap vat lieu, (layer by layer). Cong nghe nay sau do dugc phat trien rat nhanh, iing dung rgng rai trong cac ITnh vuc hang khong vu tru, cong nghiep 6 to, tau thiiy, quan su va y hgc [1], Uu diem vugt troi cua cong nghe la tao hinh san pham ma kh6ng can quan tam den do ciing ciia kim loai, hgp kim hay gom sir; co do chinh xac cao ve hinh dang, kich thuac, tuy nhien do bong be mat khong cao, trong mgt so truang hgp can phai qua qua trinh hau xii ly gia cong ca. Ngoai ra, cong nghe nay ciing ton tai mgt so nhugic diem nliu dl hinh thanh vet mit trong ket cau vat the, gia thanh san pham cao, do do chi phii hgp cho viec che tao nhung chi tiet quan trgng ma cong ngh$ truyen thong kho che tao [2].
Trong qua trinh t^o hinh bing cong nghe LDMF, duang dan la dan vi ca ban di hinh thanh nen vat thi. Cac dac trung vi kich thuoc, hinh dang hinh hgc eiia duang don nay anh huong true tiep din chat lugng san phim. Do do, nghien ciiu quy luat anh huong ciia cac tham so cong nghe den cac dac trung vi kich thuac mat cat ngang duong don, tir do tim ra pham vi tham so cong nghe hgp ly, day la co so de n ^ g cao chit lugng san pham. Hien nay, co mgt so nghien ciiu nang cao do chinh xac san pham thong qua toi uu hoa tham s6 cong nghe [3-5], tuy nhien de tim dugc ph^im vi tham s6 cong nghe hgp ly, can tien hanh mgt so lugng lan cac thi nghiem. Cac tac gia lira chgn loai
• Hoc vien KTQS.
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Tgp chi Khoa hgc va Ky lhugt.-S6 166(2-2015) - Hoc vien KTQS
vat lieu la hgp kim chiu nhiet DZ125L lam dii tugng nghien ciru, day la loai vat lieu dugc ung dung rit nhiiu trong nganh hang khong vu tru va cac nganh cong nghiep trgng diim khac [6-7], xay dung mo hinh cong nghe ve kich thuoc theo mat cat ngang duong don, lam co so de lira chgn cac tham so cong nghe khi tao hinh. Sir dung mang true giao trong quy hoach thuc nghiem de tim ra quy luat anh huong cua cac tham so cong nghe den kich thuoc duong don, tir do xac dinh pham vi tham so cong nghe hgp ly de tao hinh duang don eo chieu rgng w ^ 0,5^0,55 mm; chieu cao h = 0,09-^0,11 mm.
2. Xay dung mo hinh toan hoc kich thuoc theo mat cat ngang duong don De xay dung quy luat anh huong cua cac tham so cong nghe den dac trung ve kich thuoc va hinh dang (do rgng, do cao) theo mat eat ngang eiia duang don dua vao dinh luat bao toan khoi lugng va quy luat phan bo nong do hat hot vat lieu trong khong gian.
Bot vat lieu dugc dong khi dua tir buong cap bot den dau phun, su phan bo nong dp dong bot trong khong gian do dac trung ve ket cau cua dau phun quyet dinh, cu the la goc nghieng ciia ranh cap hot, do r6ng ranh [8]. Dua vao ket cau cua dau phun thiet lap mo hinh vat ly va tim ra quy luat phan bo nong do cua bot vat lieu trong khong gian, xac dinh dugc cong thiic tinh chieu rgng, chieu cao ciia duong dan.
(•••) ::l (b) °"«'»' "™'"i" >."«
Hinh 1. Md hinh ddu phun vgt lieu: (a) Hinh dnh ddu phun; (b) Mo hinh ddu phun.
Dinh nghTa cac dai lugng tren hinh 1(b) nhu sau:
0 | la vi tri tam viing hpi tu cua chiim tia laser;
02 ia vj tri tam viing hpi tu cua dong hot;
03 la vi tri tam viing ket tinh cua dong hot vat Heu (vi tri tam viing nong chay).
Dat diem O3 lam goc tga do, khi vi tri hpi tu ciia dong bpt va vi tri ket tinh khong triing nhau (02#03) thi ggi khoang each giira hai diim nay la Zp, gia tri Zp phu thugc vao khoang each thuc ti giua hai diem O2 va O3. Niu diim kit tinh O3 nim phia tren diem hgi tu dong hot O2 thi gia tri Zp < 0. Niu diim kit tinh O3 nim phia duai diim hgi tu dong bot O2 thi gia tri Zp> 0.
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Journal of Science and Technology.-N. 166(2-2015) - Military University of Science and Technology
Tren hinh 1(b), cac viing 2 va vung 3 hat bot vat lieu phan b6 theo quy lu$t Gauss [9], phuong trinh phan b6 n6ng do bflt vat Hfu trong khong gian nhu sau:
m(x,y,z)= i—e^ "•=' J (1) 2M.
7tV^R\z)
iVlo hinh toan hoc do rpng duong don nhu sau:
J ..(i-,).(z)- r ^^^
Mo hinh toan hoc do cao ducmg don nhu sau:
^_JriM^^ (3) AR-\z)V,p
trong do,
vf - do rpng duong don (mm);
/? - do cao duong don (mm);
R{z) - khoang each tu diem ngoai cimg dong bot den tam dong bot tai mgt diem bat ky theo phuong Z each tam hgi tu dong hot mpt khoang Z (mm), gia tri cua R{z) phu thupc vao gia tri Zp;
Mp - lugng cap bot (kg/s);
P - cong suat nguon laser (W);
tt - he so hap thu nang lugng ciia vat lieu doi vai tia laser, a ^ 0,35;
rp - he so phan xa nang lugng ciia vat lieu, rp = 0,09;
d{z) - duong kinh vang laser 6 vi tri hgi tu chiim laser la Z (mm);
T,„ - nhiet do viing nong chay ("C);
To - nhiet do ban dau ^C);
>i - he s6 phu thugc vao he s6 truyin nhiet cua vat lieu;
Vs - toe dp quet dau laser (mm/s);
p - mat dp bot vat lieu (kg/m^);
Cp' nhiet dung rieng cua bot vat lieu (J/(kg.'^C));
rj - hieu suit sii dung vat lieu (77 = 0,2-^0,4).
Tir cong thiic (1) va (2) co thi thiy do rgng va do cao cua duong don la mgt ham so ciia cac tham so nhu cong suit laser, tic dp quet chiim laser, duong kinh ving hoi tu chiim tia laser, he so hap thu nang lugng ciia vat liSu voi tia laser, he s6 biic xa cua VEit 44
Tgp chi Khoa hgc vd Ky thugt -Sd 166(2-2015) - Hgc vi$n KTQS
lieu voi tia laser, nhiet do ban dau cua vimg nong chay va cac tham so nhiet vat ly ciia vat lieu.
Dua vao mo hinh toan hgc kich thuoc mat cat ngang duong don va mgt so thi nghiem so bg ban dau xac dinh pham vi tham s6 cong nghe di tao hinh duong don theo cac tham s6 cong nghe trong bang 1. Sau do, danh gia sy anh huong cua cac tham s6 cong nghe din cae chi tieu vi kich thuoc duang dan, tim ra pham vi tham s6 cong nghS hgp Iy.
Bdng I. Pham vi cdc tham so cdng nghe thi nghie Tham so
cong nghe Gia trj
Cong suat laser P/(W) 200 + 290
T6c dp quet Vy{mm/s)
6 + 1 2
Lirgng dp hot Mp/(g/phLit)
4,5 + 7,5
Khoang each Zp/(mm)
-2+ 1 3. Thi nghiem
3.1. Phirffng phdp thi nghiem
Thiet bi thi nghiem nhu tren hinh 2, bao g6m: ngu6n phat chvun tia laser Nd: YAG, so hieu JK1002SM, cong suit IKW; tieu cu 160 mm, duong kinh hoi tti chiim laser 0,5 mm; may cSp bot kim loai s6 hieu DSPF-2; dSu phun cSp bot; he th6ng diSu khi&i CNC 3 true; he th6ng cip khi tro Argon va mot s6 thiSt bi trg giup khac.
Htnh 2. Sa do vd thiet bi thi nghiem: (a) So dS nguyen ly: (b) Thiet bi thi nghiem.
Vat lieu thi nghiem: T t o nSn sir dung loai hop kim chiu nhiet DZ125L dang tSm, kich thuoc 150x100x8 (mm); vat heu tao hinh su dung hop kim chju nhiet DZ125L dang bot, thanh phan hoa hoc vat lieu hop kim chiu nhiet DZ125L nhu bang 2. Can cil vao so lieu tinh toan xac dinh cac tham s6 cong nghe so bo nhu bang 1,
Muc tieu la xem xet miic dp anh huong cua b6n tham s6 cong nghe nhu trong bang 1 dSn kich thuac mat cSt ngang duong tao hinh don (do rpng w, dp cao h), sau do tim ra pham vi tham s6 cong nghe hop ly dS tao hinh dupe duong dcm co kich thuoc:
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Journal of Science and Technology.-N.166(2-2015) - Military University of Science and Technology
chiau rpng w = 0,5-i-0,55 mm; chiSu cap h = 0,09+0,11 mm, khi tao hinh chi tiet hop kim chju nhiet DZ125L bing cong nghe LDMF vol cac duong don co kich thudc nhu tren se dam bao dupe dp chinh xac hinh dang, kich thuoc san pham [10].
Phuong phap: Can cir vao nlumg kSt qua nghien ciru ve cong nghS LDMF [11-12], cac ySu t6 anh hucmg toi cac chi tieu chdt luong tap hinh dpc lap voi nhau, xet 4 yeu to anh huong, m6i ySu t6 co b6n mirc, do do ik tai sii dung mang true giao Li6(4 ) trong quy hoach thuc nghiem dS danh gia mirc dp anh huong ctia cac yeu to c5ng nghe den kich thuac duong dcm, d6ng thoi can cir vao kk qua thi nghiem tim ra pham vi tham so cong nghe hpp ly dam bao chi tieu v8 kich thuoc duong don. Cac yeu to anh huong va cac mirc nhu trong bang 3.
Bang 2. Thanh phdn vgt lieu hap kim chiu nhiet DZ125L (%)
c
0,09 Cr 9,70
Co 9,64
Mo 2,18
W 7,14
Al 4,90
Ti 3,12
Ta 3,78
B 0,015
Ni Can bang Bdng 3. Bdng cdc yeu td dnh hic&ng va so mirc
Mirc
1 2 3 4
Yeu to anh huong Cong suat laser
P/(W) 200 230 260 290
Toe do quet V,/(mm/s)
6 8 10 12
Luong cap bot Mp/(g/phut)
4,5 5,5 6,5 7,5
Khoang each Zp/(mm)
-2 -1 0 1 Sir dung thiet bi LDMF tao hinh 16 mau duong dan nliu hinh 3. Sau do mang cac mlu cit thanh cac mau nho (bing may cit day tia Itia dien EDM) nhu hinh 4. Sau do mang cac mlu nay di mai, danh bong de soi tren kinh hiin vi dien tu SEM, kit qua nhu hinh 5. Sau do, dua tren ket qua thi nghiem tien hanh phan tich, danh gia su anh huang eiia cac tham so cong nghe den cac chi tieu tao hinh, xac dinh pham vi tham s6 cong nghe hgp ly, thi nghiem kiem chiing vai cac tham s6 cong nghe hgp ly.
3.2. Ket qua thi nghiem
Ket qua thi nghiem tao hinh 16 mlu the hien tren hinh 3.
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Tgp chi Khoa hoc va Ky ihiidl.-SS 166(2-2015) - Hoc vidn KTQS
Hinh 4. Mdu dirge cat nhd Hinh 5 Hinh anh mau tren kinh hien vi dien tu SEM Ket qua do kich thuoc mat cat ngang ciia cac m l u the hien trong bang 4,
Bdng 4. Ket qud thi nghiem
So till nghiem
1 2 3 4 5 6 7 8 9 10 I I 12 13 14 15 16 R.,(li)
Y i u 16 anh hirang Cong suat laser
P/(W) 1 1 1 1 2 2 2 2 3 3 3 3 4 4 4 4 0,065
Toe d6 quel Vy(mm/s)
2 4 4 2 3 1 1 3 1 3 3 1 4 2 2 4 0,063 Muc do anh huong R,.(w) 1 0,068 1 0,012
Miic dQ anh huong
Luong c§p hot M/Cg/phiit)
3 1 3 1 1 3 1
J
4 2 4 2 2 4 2 4 0,023
Khoiing cdch Zp/(mm)
3 2 4 1 4 1 3 2 2 3 1 4 1 4 2 3 0,028
Ket qua thi nghiem Oo cao h/(mm) 0,08 0,065 0,07 0,085 0,068 0,13 0,14 0,1 0,14 0,16 0,13 0,13 0,06 0,09 0,075 0,09
Dp rong w/(mm) 0,54 0,48 0,51 0,46 0,55 0,53 0,53 0,51 0,52 0,52 0,55 0,59 0,55 0,57 0,56 0,58 P > V , > Z „ > M „
0,05 1 0,025 1 1 P > M „ > Z „ > V ,
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Journal of Science and Technology.-N. 166(2-2015) -Military University of Science and Technology
3.3. Thao luan
De danh gia miic dp anh huong ciia cac yeu to cong nghe d^n kich thuac ducmg don, ta sir dung phuang phap phan tich sai so Ion nhat Rm(i) (m la ygu to, i la chi tieu), yeu to CO sai lech R(i) cang cao thi mirc dp anh huang cua no den chi tieu cang lan va ngupc lai. Ket qua thi nghiem the hien trong bang 4.
3.3. J. Anh humig ciia tham so cong nghe den do cao dumig dan tao hinh Can cii vao ket qua thi nghiem nhu bang 4, mirc dp anh huang cua cac tham so cong nghe den dp cao duong don lan lupt la cong suat laser > toe dp quet > khoang each giua vi tri hpi tu dong bpt va vi tri vung nong chay > lupng cap bpt.
Hinh 6. Anh hicdng ciia cdc tham s6 cong nghe dSn do cao duang dan Anh huong ciia cong sujt laser din dp cao duong don tuong d6i phirc tap, thong qua ket qua thi nghiem cho thay cong suit laser phai duy tri a mpt phjm vi nhit dinh.
Neu cong suat laser qua nho se khong thS khiln cac hat bpt vat lieu trong vung nong chay bi nong chay hoan toan, anh huang din chit luang tao hinh; con nlu cong suit laser qua lan co the lam tang dp sau cua viing nong chay, site cang bl mjt nho hon trpng luc din din hien tuong kim loiii tran sang hai ben truoc khi kit tinh lam tang chilu rpng duang don. Do do, cong suit laser phai duac sir dung a mpt pham vi thich hop nhat dinh. Theo yeu cau do cao duang dan h co gia tri khoang 0,1 mm nen cong suit laser hctp ly nim trong khoang 220+230 (W).
Sir anh huong ciia toe dp quet din dp cao duang dan tuang dii dan gian. Khi tang toe dp quet, se dan den lam giam luong bpt vat lieu tham nhap vao viing npng chay trong mpt don v] thai gian, do do lam giam dp cao duong don, con nlu tic dp quet nho qua se lam tang lupng bpt trong vimg nong chay dan din tang dp cao duong dan. Theo yeu cau ve dp cao duang dcm thi tic do quet hap ly nim trpng khoang tir 8+10 (mm/s).
Vi tri hpi tu cua dong bpt so voi vi tri viing nong chay co anh huong lan din dp cap duong don Hinh 1(a) thi hien vi tri hpi tu cua dong bpt va xac djnh he tpa dp OXZ.
Khi vi tri hoi tu dong vat lieu triing vai vi tri viing nong chay (Z = 0) thi dp cap duang don CO gia tri Ion nhat, khi vi tri hpi tu cang xa vi tri vimg nong chay (ca vl hai phia) thi 48
Tgp chi Khoa hgc vd Ky thiidL-Sd 166(2-2015) - Hoc vien KTQS
do cao duong dan giam din. Theo yeu ciu ve do cao duong don, Zp hgp Iy nam trong khoang -2 - -1 mm hoac 0,5 -^ 1 mm.
Doi voi tham s6 luong elp bot, khi tang luong cap bot thi lugng bot vat lieu tham nhap vao vimg nong chay cung tang len, do do lam tang dp cao duong don. Tuy nhien, trong mpt pham vi nang lugng laser nhat dinh thi so luang bot vat lieu bj nong chay cung chi la mpt so lugng hiiu han nhat dinh (do mgt don vi nang luang laser chi co the lam nong chay mgt so lugng nhat djnh bpt vat lieu), do do, trong dieu kien cong suat laser va toe do quet nhat dinh, chi eo the lam nong chay mot so luong nhat dinh hot vat lieu, neu lugng cap hot qua Ion co the lam cho eac hat hot vat lieu trong vimg nong chay khong bi nong chay hoan toan, anh huong den chat lugng tao hinh. Do do, nhat dinh phai khong che chinh xac luong cap bot. Ket qua thuc nghiem cho thay khi tang lugng cap hot thi dp cao duang don co xu huong tang len. Can cir vao yeu cau dp cao duong don thi luang cap hot hgp ly nam trong khoang 5,5 - 6,5 (g/phiit)
3.3.2. Anh hitmig ciia tham so cong nghe den dp rong diimig dcm
Can cir vao ket qua thi nghiem nhu bang 4, mirc dp anh huang ciia cac tham so cong nghe den do rong duong don lan lugt la cong suat laser > lugng cap bot > khoang each giiia vi tri hpi tu dong bpt va vi tri vimg nong chay > toe do quet,
05S -1 I 0 3 6 •
200 230^260 290
Coag smal laser 5 a 10 12
Toe do qmet ng cap bot Kkoaag cick 7^
Hinh 7 Anh hu&ng cua cdc tham so cong nghe den do rong duang dcm Khi tang cong suat laser thi dp rgng duong dan tang len, con khi tang toe dp quet thi dp rpng duong don co xu huong giam xxiong, Su anh huang ciia luong cap hot den dp rgng duang don tuang doi nho, khi cong suat laser dat den gia tri dit Ion, neu tang luang cap bot thi do rgng duong don co xu huong tang len. Do la do khi tang cong suat laser va giam toe dp quet thi mat do nang lugng trong viing nong chay tang len, tir mo hinh cong nghe ve dp rgng duong don thay rang the tich vimg nong chay ciing tang len, do do do rpng duang dan tang len.
Khi tang khoang each hpi tu dong bpt so voi vi tri nong chay thi dp rong duong dan CO xu huang giam xuong, khi vi tri hgi tu dong bgt tning voi vi tri vimg nong chay thi nong dp hot vat lieu la lan nhat, do do dp rgng duong don la Ion nhit Khi thay doi
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Journal of Science and Technology.-N. 166(2-2015) - Military University of Science and Technology
vi tri tuang quan giira vimg hpi tu dong bgt va viing nong chay thi chi co the lam thay doi lugng bpt trong vung nong chay, ma su thay doi ciia lugng bgt trong viing nong chay khong lam thay doi qua nhieu den do rgng duang don, do do trong ciing mgt dieu kien cac tham s6 cong nghe khac thi su anh huong ciia vj tri tuong quan giita hai vimg nay den dp rgng ducmg dan la khong dang ke.
Can cir vao chi tieu ve do rgng duang dcm thi pham vi tham so cong nghe hgp ly nhu sau: P - 2 0 0 ^ 260 W; V ^ - 8 H- 12 mm/s; Mp= 4,5 H- 6,5 g/phiit; Zp= -2 ^ -1 mm.
3.3.3. Pham vi tham so cong nghe hap ly
Tir ket qua thuc nghiem thu dugc, qua phan tich va ket hgp voi chi tieu dat ra la do cao duang don khoang 0,09 -^ 0,11 mm, dp rpng duong dan khoang 0,5 - 0,55 mm, ta xac dinh dugc pham vi tham so cong nghe thoa man yeu cau tren nhu bang 5.
Bdng 5. Tham sd cong nghe hop ly Tham so
cong nghe Gia trj
Cong suit laser P/(W) 220-^ 230
Toe dp quet V,/(iiim/s)
8 - 10
LuQ'iig cap bot M/(g/phut)
5,5 - 6,5
Khoang each Zp/(min)
- 2 - - 1 Can cii vao bang ket qua tht nghiem (Bang 4) ta thiy vol bp tham s6 o thi nghiem so 8 cho ket qua tuong d i i tit. Tiln hanh thi nghiem kilm chimg, tao hinh ba m l u voi cimg mpt bp tham s l cong nghe (P = 230W; Vs = 10 mm/s; Mp = 6,5 g/phut; Zp = -1 mm), sau do tien hanh do kiem tra cac gia tri chieu cao, chilu rpng theo mat cit ngang duong don. Ket qua thi nghiem t h i hien tren hinh 8.
Hinh 8. Cdc mdu tao hinh trong dieu kien tham so cong ngh? hop ly:
(a) Ba dirong dan; (b) Mat cdt ngang mdu ]; (c) Mat cat ngang mdu 2; (d) Mat cdt ngang mdu 1 Ket qua do chieu rpng va chilu cao cac mau t h i hien trpng bang 6.
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Tgp chi Khoa hgc vd Ky ihugl.-Sd 166(2-2015) - Hgc vien KTQS
Bdng 6. Ket qud do kich ihir&c mat cdt ngang cdc mdu
IMau 1 2 3 Sai so A (%)
Ket qua do Dp cao h/(nim) 0,102 0,102 0,106 3,7%
Do rpng w/(mm) 0,526 0,538 0,541 2,4%
Tir ket qua do dugc cho thay sai so kich thuac mat cat ngang duang dan khi tao hinh trong ciing mgt dieu kien tham so cong nghe hpp ly d8u tuong d6i nho, sai s6 nay CO the chap nhan dugc (nho hon 5%). Do do, co th^ kSt luan: Pham vi tham s6 cong nghe nhu trong bang 5 co the tao hinh dugc cac duong don co kich thuoc 6n_dinh, dat yeu cau de ra, Pham vi tham so nay dugc diing lam co so cho qua trinh tao hinh chi ti6t thanh mong, chi tiet dang kh6i.
4. Ket luan
Thong qua xay dung mo hinh toan hgc kich thuoc duang don va su dung mang true giao trong quy hoach thuc nghiem da xac djnh dugc miic do anh huofng eiia cac tham so cong nghe den kich thuac duang dan trong cong nghe LDMF nhu sau:
1) Muc do anh huang cita tham so cong nghe den dp cao duong dan nhu sau:
cong suat laser > toe dp quet > khoang each giira vi tri hgi tu dong bgt va vi tri vimg nong chay > lugng cap bgt.
2) Miic do anh huong ciia cac tham so cong nghe d^n dp rpng duong don ISn lugt la cong suat laser > lugng cap bpt > khoang each giira vi tri hpi tu dong bpt va vi tri viing nong chay > toe dp quet.
3) Xac dinli dugc pham vi tham so cong nghe hgp ly tao hinh duang don nhu trong bang 5. Pham vi tham so cong nghe nay lam co so cho qua trinh tao hinh cac chi tiSt khac.
Tai lieu tham khao
1. Chua C. K., Leong K. F., LIM C. S. Rapid prototyping principle and applications. World Scientific, Singapore, 2003.
2. Y. P. Katlniria. Some aspects of laser surface cladding in the turbine industry. Surface and Coatings Technology, 2000 (132), pp. 262-269.
3. Wu X., Mei J. Near net shape manufacturing of components using direct laser fabrication technology. Journal of Materials Processing Technology, 2003, 135 (3), pp. 266-270.
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Journal of Science and Technology -N.166(2-2015) - Military University of Science and Technology
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Ngay nhgn bdi: 11 ihdng 8 nam 2014 Ngay nhgn ban sira lan cuoi: 26 thang 12 nam 2014
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