NGHIEN CUU - TRAO 001 / XnC DINH DO TiN CQY TREN CO SO MON V^ CQC BIEN PHI^P NdNG CAO DO TIN CQY cun CHflY TRiN KHUdN EP GQCH CERAMICS CUQ NHfl MQY GflCH MIKADO THQI BiNH * NGUYEN DINH
Trang 1NGHIEN CUU - TRAO 001
/ XnC DINH DO TiN CQY TREN CO SO MON
V^ CQC BIEN PHI^P NdNG CAO DO TIN CQY cun CHflY TRiN KHUdN EP GQCH CERAMICS CUQ NHfl MQY GflCH MIKADO THQI BiNH
(*) NGUYEN DINH MAN
TOM T A T
Hien nay, Nha may gach Mikado Thai Binh
dang san xuat gach ceramics tren day chuyen t d
dong cua Italia va dang ap dung tieu chuan ISO
9001-2000 trong quan ly va kiem dinh chat lu'gng
san pham Trong day chuyen do, khudn ep la mgt
trong nhufng cum chi tiet rat quan trong, lam viec
trong mdi tru'dng an mdn, ap lUc cao, ma sat va mdn
manh Bg khudn ep bao gdm: Chay tren, Chay dudi
va 4 Vanh khudn, trong do, Chay tren la mot trong
nhdng chi tie't quan trong cua khudn, quyet djnh
chat lugng san pham gach cua nha may Nguyen
nhan hdng cua nd chu ye'u la do mdn Bai bao nay
gidi thieu ke't qua nghien cUu do tin cay tren ca sd
mdn cua Chay tren; cac bien phap nang cao do tin
cay, dong thdi xac dinh chu ky thay the cua nd theo
yeu cau ve do tin cay cua ngUdi sd dung
I M O D A U
Trong cac da}" chm'en san xuat hien dai dd tin
ca}-(DTC) cd }' nghia A d cimg quan trgng Neu mdt chi tiet
hoac thiet bi nao dd trong da}- chm'en cd DTC thap
ha}- xa} ra hong hdc thi se lam dinh tre ca da}" chu}-en
san xuat
Hien na}' o Viet Nam da cd -^'ai chuc nha
ma}-san xuat gach Ceramics, cac da}- chu}'en ma}-san xuat chu
}-eu nhap tir Italia, Tnmg Qudc Trong cac da}' chm'en
(*) TnioTig Cao dang Kuili te - Ki thuat Dai hoc Thai Nguyen
dd, khudn ep la mdt trong nhiing cum chi tiet rat quan trong, lam \iec trong mdi trudng an mdn, ap lire cao,
ma sat xa mdn manh
Bd khudn ep bao gdm Cha}- tren, Cha}- dudi va 4 Vanh khudn, trong dd Cha}- tren la chi tiet rat ha}' xay
ra hu hong, thudng xm'dn phai tha}' the, ga}' anh hudng xau den qua trinh san xuat Mdt trong nhirng ngu}-en nhan ga}- ra su hong la do be mat mep ngoai tai cac gde cua khudn bi mdn nhanh, lam giam tudi thg ciia Chay
So \ di nhirng khudn ep nhap ngoai, nhiing khudn san xuat trong nude hien na}- cd tudi thg va do tin cay tuong ddi thap ngm-en nhan hong chii yeu la do mdn Mdn khudn ep ndi chung chu }-eu la mdn do cao xudc
ket hgp xai mdn hoa hgc Hien na}', Nha ma}' gach
Mikado (Thai Brnh) dang san xuat loai gach nay tren da} chu}'en tu ddng cua Italia va dang ap dung tieu chuan ISO 9001 - 2000 trong quan ly va kiem dinh
chat lugng san pham Vi xax, DTC cua cac chi tiet va
cac thiet bi trong da} chu}'en cang trd nen quan trgng
De nang cao sire canh tranh, hien tai, Nha may dang su dung khudn ep san xuat trong nudc (Nhu khudn cua Cdng t}' Kim Thinh, Cdng t}- Lien doanh San xuat khudn ep FOSHAN, ) Cho den na}-, a Viet Nam van chua cd cdng trinh nao nghien cim ve DTC cua khudn
ep gach Ceramics dua tren ca sa mdn dugc cdng bo Vi
\'a}' \'iec nghien cim DTC tren co sd mdn cua Cha}' tren khudn ep gach Ceramics cd y nghia khdng nhd ve gia
tri khoa hgc xa thuc tien Cac ket qua cdng bd da giiip
cho nha ma}' xac dinh dugc chu ky tha}- the cua
Cha}-tren khudn ep gach Ceramics theo yeu cau xe DTC cua
ngudi su dung, ddng thdi nha che tao khudn hoan toan
cd the biet dugc chat Iugng khudn cua minh de cd bien phap de nang cao do tin ca} cua khudn
TAP CHI c a KHi VIET NAM V So 1+2 - Tliang 1+2 nam 2011
Trang 2NGHIEN CUU - TRAO DOI
n N O I D U N G VA PHU^OTVG P H A P N G H I E N
ctru
2.1 Do mon Chay tren tai cff sff san xuat
Chay tren cd hinh dang nhu hinh 1
Vi tri Chay tren, Chay dudi va Vanh d trang thai
ep nhu hinh 2
Qua khao sat thuc te mdt sd Iugng ldn Chay tren
khudn ep da hdng do mdn tai cac nha may san xuat
gach Ceramics, nhu Nha may gach men Mikado (Thai
Binh), Cdng ty Cd phan Prime (Thai Nguyen), Nha
may Gach dp lat Viet-Y (Thai Nguyen) thay rang,
Chay tren mdn nhieu nhat tai be mat thanh ben la tai vi
tri lan can cac gde cua Chay
Hinh 1: Hinli anli Chay tren
1: Tam dem tren, 2: Chay tren: 3: Chay dual,
4 Tam dem duai, 5 Vanh kliuon
Hinh 2: Vi tri Chay tren, Chay duoi va Vanh
6- trang ttiai ep
Cd the giai thich dieu nay nhu sau:
Mgt Id: Mac dii nguyen lieu dugc xe cap lieu rai
deu, nhung khi dp do luc dp ldn lam cho nguyen lieu
xd ve cac gde nhieu hon, hon niia, khi thirc hien hanh
trinh ep thi Chay tren la chi tiet chu}'en dgng nen
chiu lire ma sat Idn ddi vdi Vanh khudn va vat lieu
Chay tren phai chiu ma sat rat Idn do ngu} en lieu bi
ep trong cac khe hd giiia Chay va Vanh khudn Tai
cac gde, do nguyen lieu hi dp chat hon nen ma sat Idn
hon cac vi tri khae
Hai Id: Do td chuc vat lieu tai cac vi tri lan can cac
gde kem ben -viing hon cac vi tri khae, da}- la nguyen
nhan chinh lam cho khudn mdn nhieu tai cac xi tri lan
can cac gde
Ba Id: Do Cha}- tren dugc ep xudng vdi luc ep rat
Idn (1.800 tSn) nen khi thuc hien hanh trinh ep Chay tren cd the hi ep xd ve mdt phia hoac mgt gde nao dd do anh hudng cua do ciing viing he thdng va do chinh xac lap ghep cua cac ca cau may
Bdn Id: Do ranh thoat khi trong hanh trinh ep dugc
bo tri d cac gde Chay tren nen khi khi thoat ra mang theo nguyen lieu ep dudi dang bui chuyen ddng vdi tdc
do cao la mdt tac nhan dan den cac gde cua Chay bi mdn manh hon
Ndm Id: Do sai sd lap dat, Chay dugc lien ket vdi
piston bi lech so vdi Chay dudi va ldng khudn, khe hd ban dau giiia Chay va cac Vanh khudn khdng thdng nhat, khi lam viec tai nhiing vi tri cd khe hd nhd se mdn nhanh hon Mac du da}' chi la ngu}-en nhan chu quan nhung qua khao sat thuc te cd rat nhieu Chay tren hdng bdi nguyen nhan nay (nghia la trong bdn gde Chay se
cd mdt gde nao dd cd lugng mdn ldn nhat) 2.1.L Xac dinh vi tri do mon
Qua nghien cuu ket cau cua Chay tren va khao sat thuc te hien tugng mdn ciia nd d nhieu ca sd san xuat gach Ceramics nhu da trinh bay d tren, tac gia lua ehgn phuang an do mdn tai diem M nhu hinh 3: M each gde Chay 5mm va each mep dudi ciia Chay Imm
Hinh 3: Vi tri do mon ciia Chay tren
Hinh 4: Hinh anh vung mon nhieu nhSt tren bS
mat ben ciia Chay tren va vi tri do "M"
TAP CHi c a KHi VIET NAM <• So 1+2 - Thang 1+2 nam 2011
Trang 3NGHIEN CUU • TRAO OOI
2.1.2 So dd do xax can ehgn sd lugng Cha^ la it nhat nhung \'an dam
De do luana mon Cha^ tren tai M tn nhu da xac bao dugc do chmh xac mong mudn Vi sai lech chuan o
dmh chon so dd^do mon nhu hmh 5 ^^""^ biet nen sd lugng miu dugc ehgn theo cdng thuc
s a u [ l ] [6]:
2.1.3 Dung cu do
Ddng hd so: Nhtutovo Dd chinh xac: 0.01 mm
M
Hmh 5: So do do mon Chay rren
2.1.4 Do ga dung cu do
Mdt }'eu cau dat ra trong qua tnnh do la phai do
lugng mdn cua diem M theo thai gian Dieu do cd nghia
la trong tat ca cae lan do vi tri cua dau do phai ludn ludn
trimg \ dl diem M
De thuc hien dugc dieu do tac gia da xa}' dung so
dd ga dat nhu hmh 5 \'a che tao bd dd ga ddng hd so
nhu sau (hinh 6):
Cac mat dinh vi cua dd ga la A B \ a C Tuang
img cd cac mat dinh x\ cua Cha} tren lan lugt la A",
B v a C "
Trong do:
Mat -A -.V, khdng che 3 bac tu do;
Mat B - B', khdng che 2 bac tu do:
Van C - C" khdng che 1 bac tir do
Cac mat dinh vi V B"\a C'cua Cha} phang \ a
khdng mdn
De kep ehat dd ga khi do tac gia ehgn phuang an
kep chat bang lire tir Phuong an na}' dan gian, kep chat
chac chan, tiet kiem thoi gian xa de thao tac
2.1.5 So lu-ffng Chay khao sat
Sd lugng Cha} n dugc ehgn de khao sat phai hgp
Iv Neu Im' n cang ldn thi cdng x\ec khao sat, uac lugng
cang hieu qua cang dang tm ca} Xhimg n cang Ion tin
cang tdn kem cans mat nhieu thdi gian \ a cdng sue \'i
C
M
)
B'
\ M,
5
"1
_A'
- 1
t
Hinh 6: So do 2a dat do sa dung cu do
Hinh : Hinh chieu true do cua de do aa duna cu do
Hmh 8: Hmh anh he thona do aa va duna cu do
TAP Chf c a KHI VIET NAM V So 1-2-Thang 1-2 nam 2011
Trang 4NGHIEN cuu-TRAOOOI
(I) n > u -
.s78-Trong dd: • u - chi tieu tin cay img vdi xac suat tin
ca} cho trudc (3
• s- la mdt sd du be dugc ehgn trudc sao cho vdi
xac suat do tin cay (3 thoa man xac suit P| U - n| < e,
d day:
w U - trung binh ciia mau
w |i - ky vgng cua dai lugng ngau nhien
• S phuang sai man Nd dugc xac dinh bang each
la}- sa bd mdt mau cd sd lugng m > 30 de khao sat mdn,
thdi diem do mdn: sau khi ehay may 460 gid; phuang
sai mau s- dugc xac dinh theo cdng thirc:
(2)s^ = — ^ i ; ( u , - u ) 2
m - 1 i=i
Trong dd: w u_- Iugng mdn ciia mau thu thir i
w U - gia tri trung binh ciia Iugng mdn:
(3) U = (u,+ u,+ u,+ + u )/m
m - so lugng man khao sat sa bd: lay m = 32
Theo ket qua khao sat sa bd ta cd: U = 0,099mm,
s2=0,00I68mm-
De khao sat mdn cua Chay tren khudn ep gach
ceramics, chon xac suat do tin ca}- (3 = 0,95, tuong ung
cd u = 1,96 Chgn s = 0,0I2mm Ta cd:
n > 1,96^0,00168/0,012-= 44,6945
Chgn n = 45 nghia la sd lugng Cha}- tren dugc
chgn de do mdn la 45 chiec
2.1.6 Gioi han khao sat
Khao sat lugng mdn eua Chay tren trong dieu
kien lam viec thuc te: Luc ep P = 1800 tan; Sd lan ep:
Ulan/phut
San pham gach Ceramics cd kich thudc 250inm x
200mm x 7,5 mm Mdi Ian dp dugc 10 vien
Gia thiet rang cac Chay tren dugc che tao dam bao
} eu cau ky thuat nhu nhau va quy Iuat mdn cua chimg
la gidng nhau
2.1.7 Cac bu-ffc do
Buoc 1: Lam sach cae be mat dinh vi, be mat do
tren Chay va do ga
Buac 2: Ap dd ga Ien mat dinh xi cua Cha}' va kep
chat dd ga bang lire tir (d day chgn phuong an kep chat
do ga bang nam cham vinh cuu)
Buac 3: Lap ddng hd so len dd ga va tien hanh
dieu chinh ddng hd so (theo qu}- dinh ve hudng dan su-dung), sau dd, tien hanh kep chat ddng hd so vao dd ga that each chac chan
Buoc 4: Ghi sd lieu va xac dinh ket qua do tir cac
sd lieu trung gian
2.1.8 Xac dinh lu-ffng mon gidi han U , Qua do mdn ciia 150 Chay tren khudn ep da hi Nha may loai ra do mdn (tai diem do nhu da xac dinh
d muc 2.1.1), thay rang, lugng mdn cua cac Chay tren dao ddng trong khoang tir 0,26 + 0,32mm Do vay, cd the xac dinh dugc lugng mdn gidi han cua Chay tren la: U ^ = 0,26mm Dieu nay cd nghia, la khi lugng mdn tai vi tri do > 0,26 mm thi Chay tren
bi loai bd
2.1.9 Thffi diem khao sat Khi xac dinh do tin cay tren ca sd mdn, ve nguyen tac cang nhieu thdi diem do thi do tin cay cang dugc dam bao Tuy nhien eang nhieu thdi diem do thi cang tdn kem kinh te va mat nhieu thdi gian Can cir vao lugng mdn gidi han va thdi gian Iam viec ciia khudn theo khuyen cao cua nha san xuat Can cir vao thdi gian Iam viec thuc te eua Chay tai nha may (23 gid/ ngay), chgn phuong an do Iugng mdn tai 5 thdi diem: Tai thdi diem 0 gid va sau thdi gian lam viee 230 gid,
460 gid, 690 gid va 920 gid (khoang each giiia hai lan
do lien riep la khoang 10 ngay) Tai thdi diem 0 gid lugng mdn U = 0
2.1.10 Kit qua do mon Chay tren tai co sd sdn xudt
Sau khi xac dinh ket qua do tir cac so lieu trung gian va khir cac sai sd thd ta cd bang so lieu do nhu sau (bang I)
TAP CHi c a KHi VIET NAM V So 1+2 - Thang 1+2 nam 2011
Trang 5NGHIEN cuu • TRAO 001
22 Phutmg phap xac dinh DTC cua Chay tren theo
Iuong mon [3]
Bang 1: Ket qua do mdn cua Chay tren
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Sau khi da cd sd heu thdng ke \ e lugng mon cua
Cha}- tren tai 5 thdi diem, tien hanh xac dinh DTC cua no
theo tnnh tu 4 buoc sau da}':
Buac i- Tu}'en tmh hoa cac the hien mon
Buoc 2- Xac dinh thai gian hong do mon (tudi thg
mon) cua Cha}' tren
Buoc 3- Xac dinh ham mat do phan phdi tudi tho
mon f(t)
Buoc 4- Xac dinh DTC cua Cha}- tren:
Biet ham mat do phan phdi f(t) hoac dd thi cua nd
ta hoan toan xac dinh dugc DTC cua Cha}- tren tai 1
thai diem bat k}-1 :
t
(4) R(t,,)= J f ( t ) d t = l - Jf(t)dt
23 Ket qua DTC cua Chay tren theo lutmg mon
Can cu \-ao lugng mdn tai 5 thoi diem cua Chay tren (bang 1) su dung phan mem chm en dung de thuc hien 4 buac nhu da neu a muc 2.2 cho cac ket qua sau:
- Ham mat do phan phdi tudi thg mdn f(t)
va dd thi cua nd nhu hinh 9
- Ham DTC cua Cha}- tren R(t) xa dd thi cua no
nhu hinh 9
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Hinh 9: Ham mat do phan phoi tuoi tho mon
va do thi fit) Ham do tm ca}' va do thi ham RCt)
Tu ham do tin ca}':
R(t) = l- cD[(t-1159.1633)/60,5827] (5)
{O dciy: '!>[ ] la ham Laplace, t Id then gicm Idm viec cua Chay rren den luc hong do mon) cd the xac
dinh dugc DTC cua Cha} tren sau mdi thdi gian lam
\iec nhat dinh (bang 2)
Bana 2: Bana tra DTC theo thai aian cua Chay tren
Can cu \'ao ham tin ca} R(t) \'e dugc do thi do tm
cav theo thai 2ian cua Cha^ tren
t(gia)
975
989
997
1009
1025
1035
1046
R(t) 0.9988 0.9975
i 0.9962 0.9930 0.9865 0.9798 0.9681
t(gia)
1060
1076
1090
1096 HOC
1120
1130
R(t) 0.9478 0.9135 0.8715 0.850 0.834 0.740 0.684
1 ? 1 TAP Chi c a KHi VIET NAM **** So 1-2 - Thang 1-2 nam 2011
Trang 6NGHIEN cuu-TRAOOOI
Til bang 2, ngudi su dung hoan toan cd the xac
dinh dugc chu ky thay the ciia Chay tren theo yeu cau
DTC dat trudc, ciing nhu xac dinh dugc DTC cua Chay
tren theo thdi gian Iam viec ciia nd Vi du: Mudn xac
suat Iam viec tin cay cua Chay tren dat 99,88% thi chu
ky thay the ciia Chay la T = 975 gid Vdi chu ky thay
the nay se cd 0,12% Chay tren hi hdng do mdn trong
thdi gian ay
m M O T S O BIEN PHAP NANG CAO DTC
CUA CHAY TREN
Nang cao do tin cay cua Chay tren dang la van de
cap thiet vi nd anh hudng true tiep den nang suat, chat
lugng va siic canh tranh cua san pham
Tren ea sd phan tich thanh phan hda hgc cua vat
lieu lam Chay tren va vat lieu Iam gach ddng thdi tren
CO sd do tin cay cua Chay tren da xae dinh dugc khi
chung Iam viee d thuc te hien trudng tac gia da dua ra
mdt sd bien phap nham nang cao do tin cay ciia Chay
tren sau day:
1 Doi vdi vat lieu mep Chay
Vat lieu d mep Chay true tiep tiep xiic vdi vat
lieu ep, chiu su an mdn hda hgc va mai mdn do ma
sat Vi vay, tac gia de xuat sir diing vat lieu d mep
Chay bang que ban hgp kim DS4D theo tieu chuan
JIST ciia Nhat, cd thanh phan hda hgc nhu sau: C,=
0,4%, Mn = 0,548%, Ni = 0,276 %, Cr = 13.047%,
Fe = 85% nham tang do cung va kha nang chdng
mdn cua Chay tren
2 Ve ket cau cua Chay
Do ranh thoat khi trong hanh trinh ep duge thiet
ke d cac gde Chay nen khi khi thoat ra mang theo
ngu}-en lieu ep dudi dang bui chuyen ddng vdi tdc do
cao, ngugc vdi chieu chuyen ddng cua Chay la mdt
tac nhan dan den cac gde cua Cha}- tren bi mdn manh
hon Chinh vi vay, nha san xuat nen nghien ciru giai
phap thoat khi d vi tri khae ma khdng bd tri d phan gde
Cha}- nhu hien tai
3 Doi vdi vat lieu lam gach
- Nha san xuat can phai cd ke hoach du trii ngu}-en
lieu thd tu- trudc de dat set trang thach, cd du thdi
gian phong hda
- Trong cdng doan nghien bi can phai lira chgn tdc
dd quay phii hgp lugng bi du ldn de nguyen lieu dugc
nghien nhd nhat ma van dat nang suat
- Thiet bi sang Igc rung, Igc sat tir phai dugc kiem tra, bao dudng sita chiia thudng xm en dam bao }-eu cau ky thuat vi nd cd anh huong true tiep den do min cua nguyen lieu, ngu}-en lieu cang min thi tdc do mdn khudn cang giam, do tin ca} cua khudn cang tang
r v K E T L U A N
1 Can cir vao ham tin ca}- da dugc xac dinh, hoan toan xac dinh dugc DTC cua Cha}- tren tai mdt thdi diem tuy y Tren ca so ket qua DTC dugc xac dinh, nha che tao khudn hoan toan cd the biet dugc chat lugng hudn cua minh
2 Tuy theo yeu cau ve DTC cua ngudi sii- dung, dinh ra dugc chu k}- thay the cua Cha}- tren Chgn dung thdi diem thay the cd tac dung rat ldn trong viec dam yen cau ky thuat cua Id gach dugc san xuat, ddng thdi ngudi sir dung hoan toan chii ddng ve thdi gian thay the Chay tren va cd ke hoach chuan hi day du sd lugng chay dutrir
3 Mdt sd bien phap de nang cao do tin cay cua Chay tren cd the ap dung vao thuc te san xuat
Tai lieu tham khao:
[1] Bui Cdng Cudng, Bui Minh Tri (1997), Giao trinh xac suat va thong ke irng dung, NXB Giao thdng Van tai
Ha Noi
[2] Phan Van Khdi (2001) Ca sd danh gia do tin cay, NXB Khoa hpc va KJ diuat Ha Noi
[3] Nguyen Dinh Man (2005), Luan an tien si ki thuat [4] Birolini Alessandro (1999), Reliability Engineering Theory and Practice, Springer, Berlin
[5] Birolini Alessandro (2003) Reliabilit}- Engineering, Springer-Verlag, Berlin Heidelbeg
[6].DotyL.A.(1985,I989).Rehabiht}-to the Technologies, Industrial Press, New York
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