NGHIEN cuu-TRAO001
Nghien cuii If ha nang img dung polymer concrete trong thi^t Ici vo
hop true chinh may CNC
(*) NGO MINH TUAN (**)TS BUI QUY Lire
1. Dat van de
Mdt trong nhiing yeu td anh hudng den dp chinh xac may la tinh dan hdi va dp cirng viing cua ket cau may. Mdt trong nhirng giai phap nang cao dp chinh xae may la viec lira chpn va irng dung vat lieu che tao cum may hgp ly. Bai bao de cap tdi kha nang nghien cuu va ling dung mdt loai vat lieu mdi thay the cac vat lieu truyen thdng, nham nang cao dac tinh tinh hgc va ddng lire hgc cua cau tnic may cdng cu. Mot trong nhiing cum ket cau quan trgng cd anh hudng tdi ldn tdi dp chinh xac dugc chung tdi dua vao thir nghiem dd la hop true chinh may cdng cu.
So sanh eac vat lieu khac nhau trong bang 1, cd the thay rang, lgi the chinh cua PC khi so sanh vdi gang due la he sd can dao ddng ldn ban 10 lan, cd the cai thien dac tinh dpng lire hpc eua may.
TOMTAT
Nhieu vat lieu composite cao cap da 6ugc sd dung rong rai de cai thien tinh chat khac nhau nhii: tinh giam chan, giam trong liiong, nang cao do ben, tuoi tho va tmh cdng nghe ket cau.
Polymer concrete (PC) la mot trong nhiifng vat lieu dang dUdc nghien ciiu, iing dung vao cdng nghiep san xuat may cdng cu. Bai bao nay trinh bay phuang phap xay diJng md hlnh, phan tich va so sanh dac t m h tTnh hpc, dong liic hoc cua ket cau vd hop cum true chinh, diiOc che tao tCf cac vat lieu khac nhau. Tii do, danh gia tinh Uu viet ciia vat lieu PC khi sCr dung lam vat lieu trong ket cau may cdng cu. Ket qua nghien ciiu suf ddng gdp quan trpng trong viec nghien ciiu kha nang iing dung PC trong thiet ke may cdng cu.
Bang 1: cac dac diem thong thudng ciia mot so vat lieu
Dac diem Do ben nen Do ben uon Modul dan hoi He so truyen nhiet He so dan nd dai Ty trong
He so chong rung
Dvi MPa MPa Gpa W/mK
10-«/K Kg/m3
%
Thep
250-1200 400-1600 210 45-50
12 7850 0,2
Gang due 600-1000 150-400 80-120 45-50
10 7150 0,3
Cement concrete 40-100
>3 20-40 2
10-14 1900-2800 1,5
PC 40-170 25-80 30-80 1,3-2 4-20 2100-2600
2-3
(*) Dai hpc Ky thuat Cong nghiep Thai Nguyen
(**) Dai hpc Bach khoa Ha Npi :•>::'.J . y t n j
J TAP CHI c a KHI VIET NAM V So 3-Thang 3 nam2011
NGHIEN cuu-TRAO001
2. Mo Hmh Kk C§u Va Mo Hmh Tinh Toan Vo Hop Cum True Chinh May Phay Cue Vmc65
a, Mo hinh k i t cSu
Muc dich ciia nghien ciiu la danh gia kha nang sir dung vat lieu PC thay eho cac vat lieu truyen thdng dimg trong san xuat may cdng cu. Trong nghien cim, chung tdi lira chpn ket cau cum true chinh tieu bieu dugc sir dung ddi vdi nliieu may, ddi hdi cd dp chdng rung ddng va dp chinh xac cao, dd la hop cum true chinh may phay CNC 3 true sir dung truyen dan dai rang.
De danh gia dugc kha nang img dung PC cho vd hop true chmh may phay CNC, chung tdi di vao nghien cim cac dac tinh tinlr hpe va dac tinh ddng lire hpe cua vd hop lam bang hai loai vat lieu (PC va gang) trong bai trudng hgp (Trudng hgp 1: Tinh theo che do cat thir; Trudng hgp 2: Tang lire cat len 150%). Vi muc dich so sanh kha nang img dung hai loai vat lieu, do dd, chi sir dung cimg mdt ket cau va chi thay ddi vat lieu. Md hinh 3D dugc xay dung trong phan part design ciia phan mem Catia.
- Mo hinh 1
Sir dung gang due cd dac tinh ca hpc: Dp ben nen a j„ = 1000 Mpa; Dp ben uon a j„ = 400 Mpa; Modul danh6i\|/ = 120GP<3;Hes6danndvinhietl0.10"VA:
; Ty trpng 7870 Kg/m^; He so chong rung C=0,3%.
- Mo hinh 2
Sir dung PC cd dac tinh ca hpc: Dp ben nen CTj^ =184.8il^(3;Ddbenu6naj„ = 75iWpa;Mdduldan h6i\|/ =78.896GPa;Hes6gianndvinhiet5.9.i0"''/iC
; Ty tipng 2500 Kg/in^; He sd chdng rung C=3%.
Hinh 1: Mo hinh ket ciu vo hop cum true chinh may phay CNC
b, Mo hinh tinh toan
Cac gia thiet cua md hinh tinh toan: Bd qua lire ma sat cua cac 6 true va luc quan tinh ciia cae chi tiet trong vd hop. Bd qua bien dang do nhiet sinh ra.
Cac thanh phan luc tac dung len vd hop:
- Trpng luc cua ddng ca G =51OA^
- Trpng lire cua true chinh Q = 4 1 ON - Cac thanh phan lire cat:
J J j
Fx = X(^z-cos<|), +/^..sin(t),)=P2.^cos(|). +P^^sin(|).;
1=1
j J
Fy = Z ( ^ z - s i n ' t > , -^.•C0S(!),-)=P^.2]sin(t),. - | ] c o s ( t ) ,
i = l ! = 1 , = 1
Trong do: 9 = ? vdi n: la tdc dd true chinh, i la 2nn sd rang dao tham gia cat, P^ la lire eSt tiep tuyen, P^ la lire cat hudng kinh
Trudng hgp 1: P^=1278N; P^ = 958N Trudng hgp 2: P2=1917N; P^ = 1437N -Mo men cit M^^ I OONm
- Luc do bg truyen dai tae dimg len true ddng co va true chinh : Fj = F^ =654N
- Phan lire tai ngam dd
Hinh 2: So do phan tich luc tac dimg len vo hop
3. Phan tich dac tinh tinh hoc vo hop cum true chinh may phay cnc vmc65
Cae dae tinh tinh hgc dugc xac dinh tren phan mem catia. Mue dich la danh gia dp ben tinh cua vd hop cum true chinh khi dung cac loai vat lieu khac nhau. Vi vay, chiing tdi chi xac dinh cac dac tinh tinh cua vd hop trong trudng hgp 2 (cd lire cat ldn hon).
a. Md hinh 1 (3=
TAP CHl c a KHi VIET NAM *X* S6 3-Thang 3 nam 2011
NGHIEN CUU • TRAO 001
Von Mises stress (noOal values).!
b. Mo hinh 2
Hinh 3: Mo hinh img suat tuong duong va mo hinh chuyen vi cua vo hop trong truong hpp 2
Vdi mue dich so sanh cac dac tinh tinh (chujen vi, img suat tuang duang, img suat chinh, khdi lugng, modul dan hdi) ciia hai ket eau vd hop, ehiuig tdi xay dung bieu dd tien binh 4. Ta tha}" tren phuang dien tinh hpc dac diem ndi bat nhat cua ket eau lam bang vat lieu PC la cd khdi lugng nhd ehi bang 33% so vdi khi sir dung gang. Trong khi do, cac dac tinh tinh nhu img suat tuong duang ldn nhat va chuyen vi ldn nhat van nam tiong gidi ban cho phep. Xet phuong dien tinh hpc, ed the thay rang, vdi ket cau hgp ly thi kha nang sir dung PC tiong thiet ke vd hop true chinh may phay CNC ndi rieng va tiong thiet ke may cdng cu la hoan toan kha thi.
Hinh 4: So sanh cac dac tinh finh hpc
4. Phan tich dac tinh dong luc hoc vo hop true chinh may phay cnc vmc65
Su dung phan mem catia phan tich dao ddng rieng va dao ddng cudng hire cua vd hop ddi vdi ca 2 md hinh, xet trong ca trudng hgp 1 va trudng hgp 2.
a, Dao dong rieng
Sau mdt loat cac thi nghiem, thu dugc ket qua phan tich dao dpng rieng cua hai md hmh. Khi xet den dao ddng neng, thdng thudng ehi quan tam d^n 3 dang dao dpng rieng dau tien: md hinh 1, su dung gang (fl=257 Hz, f2= 348Hz, f3= 668Hz); md hmh 2, sir dung PC (fl= 249 Hz, f2= 343Hz, f3= 684Hz); Nhu vay, hai md hinh cd 3 tan sd dao ddng rieng xap xi bang nhau va du ldn de dam bao khi ma^" boat ddng vd hop dao dpng ngoai vimg cpng hudng.
b, Dao dong cirdng birc
Dudi su hd trg cua phan mem xac dinh dugc md
hinh ling suat tuong duong va md hinh chuyen vi cua vd hop img vdi timg thdi diSm. Thdng qua cac md huih, xac dinh dugc img suit tuong duong, chmen vi cua cae phan tu tren md binh. Thdng qua md binh ciing xac dinh dugc iing suat tuong duang ldn nhat tren vd hop va chuyen vi ldn nhat tai vi tri dat luc ck nhu sau:
+ Truang hop I: .,,,[,.
- Md hinh 1 (sii dung gang)
Ung suat tuong duong ldn nhat a , , _ = 0.836 A^/mm^
Chuyen vi ldn nhat 8 ^^^^^ = 13.5 |I?M - Md hinh 2 (Su dung PC)
Ung suat tuong duong
> / • )
ldn nhit
^„^^=QM\N/mm'-
Chuyen vi ldn nhat &^^=l7.3[im + Truang hop 2:
- Md hinh 1 (sii dimg gang)
Ung suat tuang duong ldn nhat
^r^max =29.3N/mm'
Cbuj'Cn vi ldn nhat s ^ ^ = 47.5)Lim - Md hmh 2 (Sir dung PC)
ung suat tuong duong ldn nhat
^.^max ^30.4N/mm^
Chuyen vi ldn nhat 8^^^^ = 73.5|iw
Trudng hgp 1 thi iing suat tucmg duang ldn nhat trong hai md hinh la xap xi bang nhau, nhung gia tri chujen vi ldn nhat tiong md hinh 1 bang 78% so vdi md hinh 2. Nhu vay, ve dp ciing dpng lire hpc thi md hinh sir dung gang la tdt bon. Dieu nay cang the bien rd trong trudng hgp 2 gia tri chuyen vi ldn nhat eua md hinh 1 bang 64,6% so vdi md hinh 2. Vi vay, neu sir dung PC thi can thiet ke lai ket cau lam tang dp cimg eua vd hop.
De so sanh kha nang giam dao dpng cua hai md hinh ta xet sir bien ddi gia tri chuyen vi ldn nhat tai vi tri diem dat lire eat cua hai md hinh va lap do thi hinh 7.
|--- Poiymi lec concrete • gang
V V
a, Truang hpp 1
TAP CHI c a KHf VIET NAM V So 3 - Thang 3 nam 2011
NGHIEN cuu-TRAO001
I —- Polymer concfele -*- B3"g •
0.25 0.3 0.35 O.fl
b, Truong hpp 2
: • Hinh 7: Chuyen vi lon nhSt trong vo hop
Trong khoang thdi gian rat ngan thi gia tri chuyen vi ldn nhat tai diem dat lire eat thay ddi theo thdi gian, nghia la, vd hop dao ddng. Sau mpt khoang thdi gian thi gia tri chuyen vi ldn nhat se dan dn dinh. Vdi vd hop lam bing PC thi sau 0.05s va vd hop lam bang gang thi sau 0.37s thi gia tri chuyen vi dn dinh. Vi vay, ket cau vd hop lam bang PC cd kha nang dn dinh dao ddng tdt hon so vdi ket eau lam bang gang.
Nhu vay, xet ve phuang dien ddng lire hpc thi vat lieu PC cd nhung uu diem ndi trdi ve kha nang dn dinh dao ddng so vdi vat lieu gang due. Trong khi, tan sd dao ddng rieng cua ehi tiet du ldn de dam bao chi tiet lam viee ngoai vimg xay ra hien tugng cdng hudng. Do dd, viec sir dung vat lieu PC trong thiet ke vd hop true chinh may phay CNC la hoan toan kha thi va nang cao duge do chinh xac eua may.
5. Ket luan
Viec thay the gang due bang vat lieu PC da dugc kiem tra bang nhieu thi nghiem tien cac khia canh khac nhau.
Vdi ciing ket eau nhung khi dimg vat lieu PC tbi khdng lam giam cac dac tinh tinh hgc hien cd ma cdn tang kha nang dn dinh dao ddng cua ket cau va giam 70% khdi lupng.
Dieu nay cd y nghia vd cimg quan tipng, nhat la vdi hop cum true chinh cong xon. Tuy nhien, de dam bao dp cimg viing cua vd hop lam bang PC kbi lam viec vdi che dp ngoai lire ldn thi can thiet ke lai ket cau cho phu hpp. •
Tai lieu tham khao:
1. AndrewD. Dimarogonas, W. Valrn, Mac/iine Design A Cad Approach, Mechanical Design Washington University.
2. E. Salje, H. Gerloff, J. Mayer, Comparison of Machine Tooi Elements Made ofPoiymenAnmis of Ihe CKP, Vol. 37/1/1988,381-384.
3. F. Mason (2000), Cast Poiymer Machine Bases, Machine Shop Guide Mag., Vol.5, Issue6.
4. Ngo Nhu Khoa, Trin Ich Thinh (2007), Phuang phdp phdn tit him han, NXB Khoa hoc Ky thuat, HaNpi.
5. L.N. Lopez de Lacalle,A. Lamikiz, Machine toois for high performance machining, Girona, Spain.
(Tilp theo trang 23)
0 1 0
•
so
• \
1 0 0 I S O 2 0 0 ^ ~»2SO 3 0 0
N a n g lii-Q-ng b o c t 3 c h W
Hinh 5: Quan he giua nang lupng boc tach W voi sai so kich thuoc A img voi bien dang gia cong hinh tron (trang thai nhiet luyen)
Tir cae ket qua bieu dien d hinh 2, 3, 4 va 5 ta ed the nhan thay rang, khi tang nang lupng bde tach W thi tri tuyet ddi cua sai sd kich thudc giam dan. Tuy nhien, neu tiep tuc tang nang lupng bdc tach W thi tri tuyet ddi cua sai sd kich thudc lai bat dau tang. Dieu nay chung td rang, ludn tdn tai mpt mien nang lupng tdi uu W ma d do tri tuyet ddi eua sai sd kieh thude la nhd nhat.
Neu so sanh mien nang lupng tdi uu ddi vdi cimg 1 tiang thai vat lieu nhung bien dang cat khac nhau (chir nhat hoac hinh tidn), thi cd the nhan thay rang, mien nang luong tdi uu cho cac bien dang eat khac nhau la tuong ddi gidng nhau.
Tuy nhien, neu so sanh mien nang lupng tdi uu ddi vdi eac frang thai vat lieu khac nhau (trang thai gdc va trang thai nhiet luyen) thi cd the nhan thay ro rang rang, mien nang luong tdi uu cho cac tiang thai vat lieu khac nhau la khac nhau.
4. K e t l u a n /i, i,:,;iv;,.:
Cac thi nghiem bude dau da chi ra anh hudng ciia nang lupng bdc tach W tdi sai sd kieh thudc khi gia cdng cat day tia liia dien. Cac ket qua ciing chung mmh, ludn tdn tai mdt mien nang lupng tdi uu ma d dd sai sd kieh thudc la nhd nhat. •
Tai lieu tham khao:
[1] KONIG, W.: Fertigungsverfahren , Band 3: Abtragen, VDI-Verlag, Diisseldorf 1990.
[2] Lierath, F , Popke, H., Busack, U.:
Zu ausgewahlten Ergebnissen und Entwicklungstrends der Abspan- und Abtragtechnik. Wissenschaftliche Zeitung der TU
„Otto von Guericke" Magdeburg. 35 Heft 4,2005
[3] KNOSEL,E.: Drahterodieren vonHartmetallmiterhohter Produktivitaf bei Sichenmg der MaBhaltigkeit und minimaler Randzonenschadigung, Arbeitsbericht TU Dresden, 1996
So 3-Thang3 nam2011
