NGHIEN CCKU - TRAO OOl
LLFA CHON DIEU KlEN MAI CHO HOP KIM TITAN TI-6AL-4V
B A N GPHl/ONG PHAP TAGUCHI
SELECTION OF GRINDING CONDITIONS FOR TITANIUM ALLOY TI-6AL-4V BY USING TAGUCHI METHOD
ThS. Pham Vu Dung', GS.TS. Dao Van Hlfp' 'Tniong Bai hoc Kinh te Ky thuat Cong nghiep
^HQC vien Ky thuat Quan sir T 6 M T A T
Nhff CO cdc tinh chdt ca ly tuyet v&i, hap kim Titan Ti-6Al-4Vdutyc sti dung rang rai trong cong nghiep hang khong vH tru, dgc biet la trong che tgo cdc chi tiet cua dong ca turbine. Tuy nhien, day cung Id hap kim ci^c ky kho gia cong. Trong truong hap mat, viec xac dinh mot bo cdc dieu kien gia cong hap ly van con gap kho khan.
Trong nghien euu nay, phuangphdp Taguchi, mat cong cu co hieu lice vi toi uu hod thiit Jte theo chi tieu chdt luang, da duac img dimg de xdc dinh dieu kien mdi toi uu theo tieu chi dQ nham be mat nho nhat. Quy hoach thi^c nghiem dua tren mang true giao L9 v&i cdc bien vdo la vgn toe ctia dd, da hat ciia da vd kieu boi tran. So sdnh giua cdc kit qud tinh toan vd thuc nghiem cho thay chung kha phu hap vai nhau, cho phep khang dinh do tin cay ctia mo hinh.
Tir khod: Mdi; Taguchip; Do nham be mat; Mang trt^c giao, titan.
The titanium alloy Ti-6Al-4Vis used widely in aerospace industry, especially in manufacture ()f difference turbo-engine parts, because of its excellent mechanical and physical properties. However this alloy is extremely difficult to be machined In the case of grinding, it is still difficult to select a right combination of grinding conditions.
In this investigation, Taguchi method, a powerful tool to design optimization for quality i>
used to find optimum grinding conditions with respect to minimum surface roughness. Experiment!!
are designed with L9 orthogonal array with input variables as wheel speed, wheel grain size and coolant type. Comparisonsbetween model's output and experimental results show a good match, allowing to confirm the reliability of the model.
Keywords: Grinding; Taguchi; Surface Roughness; Orthogonal array; Titan.
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NGHIEN CUfU-TRAO D 6 |
1. DAT VAN DE R nho nhat.
Vcri nhieu tinh chat ca, ly, hoa quy bau:
Nhe x4p xi mot mia thep nhung dp hen ca hpc gan gap d6i, ke ca a iihi?t dp cao; Tra trong nhiSu moi trucmg hoa hpc nhu nuoc bien, axit, kiSm;
Than thiSn voi ca thS s6ng va khong hi ca fhk dao thai,.. .Cac hop kim Ti duac iing dyng rpng rai trong c6ng nghiep h^ng khong vu tru, hang hai, thyc phim, hoa hpc, y td,... Tuy nhien, do tinh deo, dai, din nhift kem, nhiet dung Ion,...
Cac hap kim Ti cho dSn nay van din dau nhom vat lieu kho gia cong. Hap kim Ti-6A1-4V la hpp kim 2 pha (a-p), chua co d6i thu canh tranh trong cac cum chi tiet nhe, bSn nhiet cua cac dpng ca turbine. De tai gia cong hpp kim nay da tra thanh diem nong tCr niia th6 ky qua va din nay van chua co dau hieu ha nhiet [1], [6], [9].
De tai xac dinh che dp cat hop kim Ti da thu hiit dong dao cac nha nghien ciju [1L[5],[8],[9]. Dieu nay dl hieu, vi che dp cit
^ih huong true tiep va manh nhat den cac chi tieu kinh te, ky thu$t gia cong. Xac dinh che dp cat dl dam bao chi tieu kinh te, ky thuat la bai toan cong nghe tuang doi de giai. Xac dinh cac dieu kien gia cong ban dau (do ga, dung cu, dung dich tran nguoi,...) thuc chat la bai toan kho han vi co nhieu lua chpn vai cac thong so va tieu chi dinh tinh, khong ro rang n6n nguai ta thuong dya vao kinh nghiem. Phuong phap nay, CO thi chip nhan dugc vdi cac v|it lieu thong thuong, nhu cac hpp kim nen sat, dong, nhom nhxmg vai hpp kim Ti thi khac, do cac phan ung phtic tap va khac thuong cua chiing. Mpt so nha cong nghiep da bay to mong muon co cac cong cu lua chpn, dMih gia cac dieu kien gia cong ban diu mpt each dinh lugng hon, tin cay han [8].
Muc tieu cua nghiSn euu nay la tao ra cong cu dl xac djnh bp dilu ki^n mai (dp hat -G^, chat tran ngupi -Cool, van t6c cua da -v^, dam bao dp nham bl mat -R^ nho nhit. Thuc chat, day la bai toan toi uu hoa dieu kien mai theo tieu chi
Vi cac yeu to dau vao ciia bai toan co the dupe m6 ta duoi dang so (vs), dang ma (G^), dang lai (Cool) nen khong the giai no bing cac cong cu tinh toan so. Trong nhiing truong hpp do, cac phuong phap th6ng ke hay suy diin bang ngon ngii noi co uu thi han. De giai quyet VMI de nay, chiing toi da thur nghiem mpt so phuong phap, trong do co phuong phap Taguchi se dugc trinh bay sau day. Kit qua dugc kilm chiing bing each so sanh cac gia tri tinh vcri cac gia tri do cua Ra va to ra dang tin cay.
2. BINH HlTCflVG CHQN DIEU KIEN MAI 2.1. Khai lu$n vg hinh thanh be mat khi mai Tuy CO che tao phoi cua cac h^t mai dugc coi la tuang tu nhu cua cac rang dao phay, nhung do su dac biet ve v^t lieu, kich thuac, hinh dang va phan bo tren mat da cua cac hat mai ma anh huong cua cac yeu to cong n ^ e den hinh hgc be mat mai rat khac bi6t so vai phay. Theo tinh toan ly thuyet [7], dp cao nhip nho trung binh khi mai.
(1) Trong do, vw (m/s) - Van toe cua phoi, V (m/s) - Van toe cua da; L (mm) - Khoang each trung binh giua cac hat mai theo chu vi cua da;
d (mm) - Duong kinh ciia da. Vai gia tri thong dung cua cac dai lupng tren thi gia tri tinh (ly tuong) cua R^ nho den miic khong the tin n6i, chi bing 1/1000 gia tri tot nhat co the dat dugc tren fliuc tl. Mat khac, theo (1) thi chieu sau cit khong anh huong den dp nham be mat, nhung tren thuc te lai co. Vay, yeu to nao da gay nen su sai khac qua xa giua dp nham ly tucmg va thuc tl? Co rit nhieu yen to khong thi tinh toan dugc baag ly thuyet, vi du dd cao ciia vat lieu (ba via)"^
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NGHltN CUfU - TRAO OOl
bi re sang 2 ben "lu6ng cay", vat Ii?u phoi va hat mai bj dinh len bS mat ph5i. Chinh anh huong ciia c4c ySu t6 "khong tinh duoc" nay khiSn do nham thuc Idn gSp nhieu Ian do nhtoi ly tuong va kho du doan truac.
i & . i S ^ : £ g 5 i i B - ' ^
(c) (d) Hinh 1: Bi m^t mdi v&i cdc dieu kien khdc nhau
Hinh 1 la anh chup tii kinh hien vi dien tii (SEM) cua bl mat mai hpp kim Ti-6A1-4V voi van toe da va che dp tran nguoi khac nhau . Tit ca cac anh deu cho thay cac "lu6ng cay" do vat li^u phoi hi re sang 2 ben. Duoi cac lop ba via do, it hay nhieu, deu co cac manh phoi va hat mai hi vui lap. So sanh hinh (a) vai (b) cho thay, khi mai kho vdi ciing chi8u sSu cit, chit lupng bl m^t xau di khi tang tdc dp ciia da. So sanh hinh (a) voi (c) cho thay be mat mai kho co ve tot hon b6 mat mai co tuoi dimg dich nhii tuong (emulsion). Ngugc lai, so sanh hinh (b) voi (d) lai cho thay mai co tuoi diu khoang cho hinh anh be m^t t6t hon khi mai kho.
Khuon kho ciia bai bao khong cho phep
giai thich cac hien tupng tren. DiSu chung toi muon a day la minh hoa co che vo cung phuc tap ciia viec hinh thanh bl mat khi mai, dac hi|t voi hgp kim Ti. Vi vay, mac du da phan tich rat sSu anh hucmg ciia cac ylu tl d6ng, hinh hpc cua qua trinh cit din dp nham be mat, Malkm [7]
vln phai thua nhan rang cac tinh toan ly thuyet chi CO tac dung dinh hudrng dieu khien qua trinh, khong thi dua vao do dl tinh toan dinh lugng cac thong s6 cong nghe. Cac quan he thuc nghiem tuy khong thi hi6n ro ban chat vat ly cua qua trinh nhung lai cho phep danh gia dinh lupng anh hucmg cua cac ylu to cong nghe dSu vao din cac thong s6 diu ra. Cac quan hediyc nghi$m ca ban cua mai dupe trinh bay ttong [l]j [2]. Voi R^, CO quan he:
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NGHIEN CUTU - TRAO D6i
(2) Trong do, h^ - Chilu day phoi tuong duang, Rj va r la cac hlng s6.
2.2. Binh hircnig ch9n dieu kifn mai theo dq nham be mat
Trong qua trinh mai xay ra tuong tac giua da, phoi va moi truong. "Moi truong" true tiep bao quanh vung mai la chit tran nguoi. Voi phoi da biet, can chpn da, chat tran nguoi va chi dp mai.
Ve dd: Mpt loat cac c6ng trinh nghien ciiu da chi ra, trong so cac loai da mai thong thuong cho hpp kim Ti thi da vdi hat mai SiC, dp cung trung bmh la phu hgp [1], [9]. Dp hat co anh huong 2 mat den do nham be mat. Da min, mpt mat giam R^; Mat khac lai tang dinh bam kien R^ tang. Vi vay, yeu to ve da mai dang quan tam 6 day la dp hat.
Ve moi truong: Co th6 lua chpn trong so 3 chat tran nguoi thong thuong: Khong khi (mai kho), dung dich nhG tuang (emulsion) va dau khoang. Nhu da chi ra tren hmh 1, moi loai chit tran nguoi co co che tac dung rieng va phu hgp vai cau tnic da va ch6 dp mai cu the. Noi each khac, chat tran nguoi can dugc chgn cung vai dp hat va che dp mai.
Chpn che dp mai thugc lop bai toan khac, dugc thuc hi$n sau khi bp ba phoi-da-moi truong da dugc xac dinh. Tuy nhien, hgp kim Ti dac biet nhay cam vai toe do cat (ciia da). M6i loai da mai va chat tran nguoi phu hop voi toe do cit nhit dinh. Noi each khac, toe dp cat chi ph6i viec chgn da va chat tron nguoi, nen chiing can dugc chpn cung nhau.
Vdi lap lu|in nhu tren, co 3 yeu to hinh thanh dieu kien mai ban dau can duoc lua chpn
la dp h^t, chat tran nguoi va toe dp cat.
3. N G H I I : N c t r u THlTC NGHIEM CHON DIEU KIEN MAI
Trong nghien ciiu nay, toi ira hoa dieu kifn cat dugc Ihuc hien bang phuong p h ^ Taguchi.
Muc tieu ciia Taguchi la thiet ke mgt qua trinh san xuat on dinh, dam bao chat lugng san pham cao, gia thanh ha bang each phan tich anh huong ciia cac yen to den muc tieu toi uu, tir do chgn Igc, loai bo cac nhan to gay nhieu l o ^ . CJuy hoach th\rc nghiem ciia Taguchi dua tren mang true giao (Orthogonal Array - OA), dam bao so thi nghiem it, nhcf do giam t6i da thoi gian v^ chi phi thi nghiem. Ban dgc co the tim hieu chi tiet ve CO so ly thuyet va iing dung cua phuong phap nay trong cac tai lieu [3]-[6].
3.1. Quy hoach thac nghiem
Bai toan cd 3 yeu to dau vao (factor):
Toe dp cat (v^), dp hat (G^) va chat tron nguoi (Cool), moi yeu to co 3 miic (level) nhu trong bang 1:
v^=[10,20,30];
4 = [20, 35, 50];
Cool = [Dry, Emul, Oil].
Bang 1: So lieu ddu vdo
Level Factor
I 2 3
T j
10 20 30
Gs 20 35 50
Cool Dry Emul
Oil Tu so lieu tren, mang true giao co ciu tnic L9 dupe thiet lap nhu trong bang 2, tuong ling 9 thi nghiem. Bang co 2 phin. Phin biln dieu khien chiia dii heu dau vao, trong do cac miic dugc ma hoa bang so khong thii nguyen 1, 2,3. Vi d\i thi nghiem dni 2(1,2,2) dupe tiln hanh^
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N G H l i N CUfU - TRAO D O I voi v^=20m/s, do hat G_=35, tuoi dung dich emultion. Ph^n s6 lieu do chiia kgt qua 3 Ian do R_. Cot cu6i cung (S/N) thuoc buoc sau.
Bdng 2: Mang true giao L9
D6i vdi bai toan cue dai (larger better) thi (3) dugc viSt:
(s/N),=-mog\j^Y.^,
1 2 3 4 5 6 7 S 9
B i ^ d i ^ Uu&i
Vl
1 1 1 2 2 2 3 3 3
Gs 1 2 3 1 2 3 1 2 3
Cool 1 2 3 1 2 2 3 1
^ Do dd nham (Rg) l U 2,12^
IM
^1J9 2i)9 . 2 ^ 1 '#2j49 2 J » 2.51 2 J I
Rfi ,1^8.
i l j 8 5 1^1 2 J 2 2 J 9 2.50 7 ^ 2 2.49
^=2JS9 Ri3 2,11
.'^
0 22,11 2 3 8 2^1 2;61 2,51 ia2
S/N Ola) -6,32 -5,34 -5,14 -6,47 -7.53 - 7 ^ -8.32 -7,97 -8,65
3.2. PhSn tich sS li^u va tii mi hod dilu ki^n mai Anh hucmg eua moi yeu to den diu ra dupe danh gia bing ti s6 S/N, dugc ggi la "ty so tin - tap" (signal-to-noise ratio).
(S/N\=\{ilog X (dB)
Trong do:
1 "'
lT,(y... ~y,f liphJn "tap"
(7)
(3)
Phep phan tich tren dva vao phuong sai s cua phep do nen con dugc goi la phan tich phuong sai (ANalysis Of VAriance - ANOVA).
Cu thi voi bai toan dang x6t: i-1-^9, u-1-^3, N=3. Phan tich dugc tien hanh theo cac buoc sau:
Buoc 1: Theo (6), tfah cac gia tri (S/N)^ (vi cue ti6u R^), ghi k6t qua vao cgt cuoi cua bang 2.
Vi du:
(^/w;,=-iofogio(M£l±M?!±^;.2,ii
Buoc 2: Tmh gia tri trung binh S/N cua cac yeu to theo timg miic, vi d\i:
-5,34-7.58-7,97^^^^^
(4)
(5)
Ket qua duoc ghi vao 9 6 tuang iing cua bang 3.
Buoc 3: Trong bang 3, Ian lugt:
- Tinh gia tri trung binh (Mean) cua moi yeu to. Vi du voi v co:
Vai: i - S6 thii tu thi nghiem, u - S6 thii tu Ian do, Nj - So Ian do. Miic nao co so S/N Ion (tm I6n, t^p nhd) dii gSn muc tieu toi uu han. Phuong an tdi uu tuong img vdi tong (S/N) Ian nhat.
Doi vai bai toan cue tilu (smaller better) thi (3) dugc vilt thanh:
(s/Nx=-mog(Yj^)
(6)m=(-5,6-7,34-8,31)/3=-7,08.
- Tinh gia tri Max cua moi yeu to. Vi dy
max(-5.60;7,34;8,31)=-5,60.
- Tinh hieu (Max-m) cho timg yeu to. Vi du vdi V:
Max-m=(-5,60+7,08)=l ,48.
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NGHIEN C U T U - T R A O D C I
- Tinh muc dp anh huong cua timg yeu Cac gia tri S/N cua cac miic va phuang to. Vi du vdri v^ co % anh hucmg = 100.1,48/ an t6i uu trong bang 3 co thi duoc bilu dien true (1,48+0,1240,56)^68,66%. quan nhu hinh 2.
Theo hang cuoi, ta thay v anh hucmg nhilu nhit din R^, tiip theo la chat trcm nguoi (Cool). Dp hat ciia da anh huong it nhit.
Buac 4: Xac dmh phuong an t6i uu. Ro rang phuang an toi uu se la tap hgp cac miic co ti so S/N Ian nhat (dat max). Nhin vao bang 3 ta thiy do la phuang an V1G2C3 (tuong iing cac 6 to mau), nghia la v^=10, G^=35, diu khoang. Gia tri S/N tuong ling cua no bing:
(S/N)^,=m+(Max^-m)+(MaXf^-m)+(Max^-m)
= Max^ +Max^+Maxc^ -2m ( 8 )
= -5.60-6,96-6.53 + 2x7,08 = ^ . 9 2
Cuoi cung, tinh ngugc theo (6), nhan dugc gia tri toi uu (min) eua R :
R/min)=10-(-^-*^''>-l ,76pm. (9) Bdng 3: Bang ANOVA
I 2 3 MeanbO
Mix (Msx^-nd
%BAittKita S/N mm
V,
-7J4 -831 -7J08 -5.60 1.48 68.66
jbkih iliBO cSc miic Gs - 7 ^ -7,25 -7^8 -€.96 0,12 5 J 3
Cool -7,52 -7^1 -7,08 -6L53 0.56 25.81
Vbaas^aa^s
vaacz
-734 233 phiinrtit in frfi Im
VK2C3
^.az 1,76
Hinh 2: Bieu dien S/N cua cdcyeu to 4. DANH GIA VA THAO LUAN KET QUA
Tu bang ANOVA (bang 3) c6 tiie tinh gia tri R^ (cot R^(t) trong bang 4) cho tit ca cac phuong an co the (27 phuang an), trong do cac hang to mau co danh so tuang iing vdi cac thi nghiem trong bang 2. Sai so tuang doi (SS%) giua gia tri tinh R^(t) vdi gia tri do RJd) kha nho, cho phep khang dinh mo hinh nghien ciiu la dang tin cay va co gia tri ling dung thuc tien. Ket qua tinh toan cung the hien gia tri R^=l,76|jm diing la nho nhat.
Bdng 4: Bdng ket qud ma rpng
Xhinglawn
^ H 10
;c 'C :-c 10 10 20 20
G a 3 5 5 0
30 3 5 2 0 50 2 0
-'^
Q>ol
1 1 1 1
2.
2 2
^ ^
1.98 2 J M 2 , 4 3 2 , 4 9 1.^0 i _ e i
2 . 3 5 2 . 3 3
R a ( ^ ^^y Tti 1 ¥1 afriam
^
G . mifmmWmA'm i :^t J l ^ ^1 T s i i m 4 '1
3 0 3 0 1 0
2 0 30 3 0
3 5 5 0 3 5
50
50 2 2 3
2 ^ 6 2 , 3 * 1,7«
•
3 2 , 2 2
2 . 4 9 ••a^afel
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NGHIEN CUTU - TRAO D6\
Tu do thi trong hinh 2 co thi nit ra mpt s6 kit luan, CO tac dung dinh huong cho nghien ciiu va ling dung cong ngh6 mai hgp kun Ti nhu sau:
v i n thuong lam. Mat khac, phuong phap Tagu-« i chi khong phai co im diem tuyet doi. Chiing toi hy vpng con co nhieu co hpi de trao d6i ve cac chii d l tucmg tii.*>
Ngay nhan bai: 12/6/2015 Ngay phan bi$n: 17/7/2015 - Khac vdi hSu het cdc hgp kim "de gia
cong", hpp kim Ti rit nhay cam vdi toe dp cat.
D I dat chit lugng be mat cao, cin dung toe dp thip. Dilu nay da dupe khang dinh bai nhieu
cong trinh nghien ciiu nhu da dan trong [1]. Xai li?u tham khao:
Ngoai ra, co t h i giai thich ngan gpn rang, hgp kim Ti din nhiet rit kem nen nhiet dp vung cat cao. Nhiet dp cao "cpng hucmg" vdi tinh deo, dai, d l dinh bam von co, khien chat lupng be mat xau di khi tang toe dp cat.
- Kich thudc ciia hat mai anh huong it nhung phiic tap d i n dp nham be mat. Noi chung, nen tranh da rit min (din din tang nhiet dp, tang dinh bam) hoac qua tho (tang chieu cao ba via).
Do hat trung binh la thich hpp, nhung cu the la bao nhieu con tuy theo che dp cat va che dp trcm nguoi cu the.
- Vai hgp kim Ti, dung dich tron nguoi la ch^ de ly thii nhung kha phiic tap. Diing dung dich de tai nhiet, giam nhiet dp chi tiet khong phai huong uu tien, vi neu van de nguon nhiet dp cao thi lam nguoi nhanh chi lam tang iing suat du, tang mit te vi be mat gia cong. Dung dau thich hgp (diu khoang dp nhot thip, d i u thuc vat CO kha nang tham thau va tao mang tot) se lam giam ma sat, giam nhiet tir nguln. Tinh chit hoa hoe cua dung dich ciing dang quan tam.
Trong bai bdo nay, chiing toi da dua ra m6t mo hinh toi uu hoa dieu kien mai theo tieu chi dp nham b l mat nho nhit. Mong mudn ciia cac tac gia la giai toa bdt cho cac nha san xuit nhiing ban khoan, kho quylt djnh khi diing trade nhieu lua ehpn dilu ki8n cong nghe ban diu cho qua hinh gia cong. D I giai quylt triet d l v i n d l kinh te, ky thuat eua qua trinh, vln cin giai cac bai toan tdi uu nhu dai da s6 cac nha cong nghe
[1]. Hiep Dao Van (1989); Optimalizace oper- ace rovinneho brouseni sUtiny VT6. Kandidatska disertadni prace, VAAZ Bmo.
[2]. Dao Van Hi?p, Pham Vii Diing (2013); Giam sat mon ciia di mai c6 iing dung mang no ron nhan t^io;
Ky ylu Hpi nghi toan qu6c lin thii 2 ve dilu khiSn (VCCA-2013).
[3]. Fraley, S., Com, M., Terrien, B., Zalewski, J.
(2015). Design of Experiments via Taguchi Methods:
Orthogonal Arrays. Retrieved from https://controls.
engin.umich.edu/wiki/index.php.
[4]. Kulekci, M. (2013). Analysis of Process Parameters for a Surface-Grinding Process Based on the Taguchi Method. Materials and Technology 47(1)105,105-109.
[5]. Kumar, N., Tripathi, H., Gandotra, S. (2015).
Optimization of Cylindrical Grinding Process Pa- rameters on C40E Steel Using Taguchi Technique.
Joumal of Engineering Research and Applications, 100-104.
[6]. Kumar, S., Batish, A., Smgh, R., Singh, T (2014).
A Hybrid Taguchi-Artificial Neural Network Approach to Predict Surface Roughness During Electric Discharge Machining of Titanium Alloys. Joumal of Mechanical Science and Technology, 2831-2844.
[7]. Malkin, S. (1989). Grindmg Technology Theory and Applications of Machining with Abravives. Ellis Horwood Limited.
[8]. Pal, D., Bangar, A., Sharma,R., Yadav, A. (2012), Optimization of Grinding Parameters for Minimum Surface Roughness by Taguchi Parametric Optimiza- tion Technique. International Joumal of Mechanical and Industrial Engineering (IJMIE), No. 2231-6477, 74-78.
[9]. Xipeng, X., Yiqing, Y., Hui, H. (2003). Mechanisms of Abrasive Wear in the Grinding of Titanium (TC4) and Nickel (K417) Alloys. Wear 255,1421-1426.
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