Nguyin v a n Du va Dtg Tap chf KHOA HOC & CONG NGHE 162(02): 195-199
K H A I T H A C H I E U U N G G I A M M A S A T D O R U N G © O N G T R O N G G I A C O N G C O R U N G D Q N G T R Q G i t i P
Nguyin VSn D\i'', Chu Ngpc Hiing', H& HQu Diic^
'Trudng Dgi hgc Ky thugt Cong nghiep - ^H Thdi Nguyin Trudng Cao ddng nghe Viet'Hdn, Vinh, Nghe An TOM T A T
Bii bao niy trinh bay mOt s6 kit qui nghien cihi thyc nghiSra vl hiSu ling giam ma sit dudi tic dOng ciia rung dgng dgc theo phuong v|n t6c trugt. M6 hlnh rung dong dgc theo phuang van t6c trugt dugc khai thac trong gia cdng khoan c6 rung dgng si€u i m trg giiip. Th\rc nghiem thong ke cho thay, m6 men phat sinh khi khoan giam din 30%. Hieu iing giim ma sit ting cuong khi nang thoit phoi, giam md men xoin mui khoan, din din giim nhigt cit va do d6, nang cao tuoi ben mui klioan. Kit qui thyc nghi$m dong vai tr6 ca sa cho vi?c phat triln cic mo hlnh ly thuylt khii quit sau nay.
Tir khoa: hiiu irng ma sdt, rung dgng, rung dgng triy giup, van t6ctru0, rung dgng sieu dm
GIOI THIEU
Hieu ling giam ma sat d o rung dpng da d u g c quan sat v a nghien cuu trong nhieu thap ky qua [1-9]. Anh h u o n g cua rung dong theo cac phuong t u o n g quan giiia be mat trugt va phuong chuyen dpng t u o n g doi bao gom:
phuong phap tuyen [1-4,9], trung p h u o n g [6, 8] trong cung mat phang nhung vuong goc nhau [7]. Hi?u ung giam ma sat do rung d p n g - da va dang d u p e khai thac tich c u e trong gia cong CO khi [10-14] va cac ITnh vvrc khac [5, 15]. Hi?u ling giam ma sat giua hai be mat try tiep xiic co ap luc phap tuyen cung da dugc danh gia bang th\rc nghi?m [16]. D|ic biet, nghien cuu cua Mellinger va cpng sy cho thay, mo men do ma sat giiia phoi, mui khoan va thanh 16 trong nhieu t r u a n g hgp co t h i Ion gap 5 ISn so voi m o men can thiet de t h u c hi?n qua trinh cat [17,18]. Ngoai ra, m o men Icm la mgt trong nhihig nguyen nhan chinh gay gay miii khoan. D o vay, vi?c giam ma sat khi khoan c6 mpt y nghTa quan trpng. Them nSa, ma sat Ion giiia dao va dyng cy co .thi phat sinh nhiet Ion, gay hi$n t u g n g dinh b i t phoi len dung cy, lam giam tuoi b i n dyng cu.
Bai bao nay giai thieu each thuc tiep c^n t h u c nghi?m danh gia anh hucmg tich c\rc cCia rung dpng vii irng dyng trong gia cong c a khi. M o hinh danh g\i anh hucmg cua rung d^ng lam
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giam ma sat trugt kho dugc phan tich. Hieu qua giam mo men ma sat khi thuc nghiem khoan hgp kim nhom d u g c phan tich thong qua ky thugt thong kS so sanh.
HIEU (mo G I A M M A SAT T R U 0 T K H 6 DO R U N G D O N G
Hau het cac nghien cii'u truac day deu thuc nghiem do ma sat thong qua mo hinh dia quay (pin-on-disk). B I mgt tiep xiic phat sinh ma sat t h u a n g la t i l p xiic diem, khong phan anh dung dieu ki?n tiep xuc trong cac bai toan thyc t l . Trong nghien ciiu nay, b l mat tiep xiic dugc thyc nghifm dual dang cac cap tiep xuc mat hinh chii V , mpt dang t i l p xuc rat ph6 b i l n trong ky thuat. Mo hinh thyc nghiem dugc minh hpa tren hinh I, H? thong ranh trupt dan huong I dugc cfl djnh tren ban may phay 10. Ban trugt 2 dugc dat len gia sao cho cac song trugt tiep xiic voi ranh trugt tren gia.
T h i l t bi tao rung 5 (mini shaker MS-20) va thiet hi do lyc 4 (loadcell M N C - lOOL) dugc bat vit CO dmh tren ban trugt i 0 ciia may phay K N U T H - V H F 3 . Thanh c h i n 5 co nhiem vy ty len loadcell va can t r a chuyen dpng tinh tiin khi ban may phay chay sang phai de (3) thu nhgn tin hieu lyc.
Hinh 2 minh hpa mpt so k i t qua thu dugc tia' thuc nghiem, Tren hinh 2(a), he s6 ma sat thuc nghiem do tai 7 gia tij van toe trugt khac nhau:
0.533xlO•^ 0.75xl0•^ l.lSxlQ-^ I . 7 l 7 x l 0 ' ^ 2.8xl0"\ 3.883x10"^ v^ 6x10"^ m/s.
Nguyen Van Dy vd Dtg Tgp chi KHOA HOC & CONG NGHE 162(02)-195-199
6. Bipitr6c6i^svSt S cam biin Vi triLVDT 10.Smmay
Hinh 1. Sa do thi nghiem do ma sdt tich hgp ccr cdu ning (b)
Hinh 2. (a) He so ma sdt phu thugc van tdc trugi khi rung
H? so ma sat/dugc hoi quy thanh ham phy thuoc v$.n toe trupt tuang doi I^(m/s):
7=0.635-73.86 f-i-6447.69 V^ (1) Hieu ung giam ma sat do rung dpng dugc minh hpa nhu tren hinh 2(b), khi van toe trupt dugc giii co djnh a muc 3.883x10"^ m/s, dong thai dugc bo sung mgt rung dpng dgc theo phuong trugt. Rung dgng dugc ngat trong mpt thai gian ngin dl lam n6i bat hi^u ung giam ma sat do rung dpng. Trong vung ®, chua CO chuyen dgng tuong doi, cho nen lyc ma sat va he so ma sat do dugc bang khong.
He so ma sat trugt khi co rung dugc bieu dien trong viing ®, gia tri do dugc khoang 0.14. Tin hieu nguon rung dgng dugc tat trong vimg ®.
De thay h? so ma sat khi tat rung dgng tang vupt bac (0.46) so voi khi co rung dpng.
HIEU UNO G I A M MA S A T TRONG GIA C 6 N G CO RUNG DQNG TRO GIUP Mac du da CO nhieu nghien ciiu danh gia anh huong tich cyc ciia rung dgng trg giup gia cong [10-14], tuy nhiSn vai tro lam giam'ma sat cua rung dpng chua dugc danh gia ro net.
Nhu phan tich trong phin gicri thieu, nghien
ci>u cua Mellinger va cpng su cho thay, trong
gia cong khoan, mo men sinh ra do mat giiia
dyng cu, phoi va thanh 16 khoan co thS Icm.,,
gap 5 lan so vai mfl men cat. Ngoai ra, mo
men Idn la mpt trong nhung nguyen nhan
chinh gay gay mui khoan. Do vay, vi?c giam
ma sat khi khoan co mpt y nghTa quan trpng. ;
Nguyin van Du va Dtg Tgp cht KHOA HQC & CONG NGHE 162(02): 195-199 Mfl hinh thi nghiem danh gia hi?u ung giam
ma sat khi khoan co rung dpng trg giiip dugc minh hpa tren hinh 3.
Hinh 3. Anh chup thi nghiem Tren hinh 3, dau phat rung sieu am dugc cgp tren mam cap may tien, tren dau rung gSn mui khoan xoan HSS. Phoi dugc ga tren mot dau true lap tren hai 6 lan. Mo men phat sinh khi khoan co xu hu6ng xoay tryc ga phoi. Mpt cam bien luc dugc ga sao cho c6 tac dyng can lai xu huong xoay nay. Gia tri lyc tac dung len cam bien dugc diing de xac dinh mo men"
do mui khoan tac dyng len ph6i trong qua trinh khoan. Gia tri mo men trong khoang thi nghiem da dugc kiem chuan bang dau do mfl men chuan thuong mai. Dau phat rung dugc noi vai nguon dien c6 cong suat 3 KW. Dau miii khoan dugc thiet lap rung d^ng vai t4n so 20 KHz, bien dp khoang 10 microraet.
Chuyen dpng ch^iy dao khi nay se bao gflm hai chuyen dpng thanh phan: (1) chuyen dpng chay dao thflng thuong va (2) dao dong cuong birc cua dau miii khoan do rung dgng truyen den. Dao dpng nay co the bieu dien bang phuang trinh sau:
A{t) = A^s\n{wt) (2) Trong do, Ao la bien dp Ion nhat cua rung dpng, trong trutmg hgp nay, Ao=\Q'^ mm. Khi do, rung dpng nay se b6 sung mgt thanh phSn van toe trugt dpc theo true miii khoan:
F; = *ii4 cos((WO (3) vai (D = 27f,/ la tin so rung dpng, f^20 KHz. Khi nay, vSn toe trugt lan nhit dugc xac dinh:
F = 2 ^ 4 = 1.26 m/s (4)
Dua tren gia tri van toe trugt bo sung kha Ion nay, co the phat bilu gia thuyet ring: rung dgng sieu am do co tan s6 Ion, nen t^o nen van toe chuyen dong tru'gt dang ke giQa dung cy va thanh Ifl, nen co the gay hieu iing giam ma sat dang kS, Nghien ciiu thyc ngluem dugc tien hanh nham kiem chiing gia thuyet nay.
Hinh 4 minh hpa mgt ket qua do mo men khi khoan, Nhu c6 the thiy tren hinh 4, trong giai doan dau, mo men tang den gia tri cSn thilt de cii gpt, dugc ghi chii la "Momen cat". Vl nguyen tac, mo men cat khflng phy thugc chieu sau 16 khoan. Tuy nhien, 16 khoan dupe cang sau thi ma sat giii'a phoi, mui khoan va thanh lo cang 16'n. Tai mgt thoi diem bat ky, phan chenh lech giii'a cac gia tri mo men nay so voi m6 men cat (coi nhu khflng dfli) chinh la mfl men ma sat, Gia tri mfl men ma sat noi chung thay d6i ngau nhien, tuy thugc xac xuat xuat hien phoi ket nhieu hay it trong ranh mui khoan.
Hinh 4. Mo men cat vd mo men ma sdt khi khoan Tiin hanh thyc nghiem cho m6t s6 che dp cat th6ng dyng khi khoan va tien hanh thong ke so sanh theo cap {paired-l lest) ma sat giu'a khoan 16 co rung dgng trg giiip va khoan kh6ng CO rung dpng trg giiip. Ket qua phan tich cho thiy, voi dp tin cay 95%, mo men ma sat khi khoan cfl rung dgng bfl sung giam khoang 30% so \ci\ khi khoan khflng co rung dflng (Xem minh hpa tren hinh 5).
Kit qua thyc nghi?m nay dat ca so kiem chii:ng cho gia thuyet ve hieu iing giam ma sat
197
Nguyin v a n Dy va Dtg Tap ch! KHOA HQC & C 6 N G NGHE 162(02): 195-199 do rung dpng. Mfl hinh dgng luc hgc mfl ta
hieu ung n a y se d u g c tiep tyc trong cac cong bo sau.
Hlnh 5. Kit qud phdn tich so sdnh K E T LUAN
Mgt nghien c u u t h u c nghiem danh gia hieu ling giam ma sat du6i tac dgng ciia rung dgng dgc theo p h u a n g vgn toe trugt dS dugc thuc hien. M u c do giam cua he so m a sat theo vgn toe chuyen dgng t u o n g doi giiia c i c be m a t trugt da dugc xac dinh. A p dyng cho bai toan cgng rung dpng c h o gia cong 16 bang p h u a n g phap khoan, thyc nghiSm thflng k£ cho thay, vcri dp tin cay tren 9 5 % , m 6 men ma sat khi khoan da giam den 3 0 % khi bo sung rung dpng sieu am tan so 20 K H z dgc theo p h u o n g tien dao. Cac ket qua t h y c nghiem se d u g c sir dyng cho bai toan phan tich dgng lyc hgc qua trlnh gia cong co rung dgng trg giiip.
Ltri c a m o n . Nghien ciiu nay d u g c tai t r g bflfi Q u J phat trien khoa hpc va c6ng ngh? quoc gia ( N A F O S T E D ) trong d l tai ma s o 107.01- 2012.33.
T A I LIEU T H A M K H A O 1. Gao H., Guo Y., Bao G. And Reynaerts D., Influence Of Vibrated Area And Normal Force On Friction Reduction Ratio Between NBR/Aluminum Couple, Tribology International 82(2015)95-100;
2. Chowdhury MA, Helali M., The Effect Of Amplitude Of Vibration On The Coefficient Of Friction For Different Materials. Tribology International 41 (2008) 307-14.
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M. and Rahaman M. L., The Effect of Sliding Speed and Normal Load on Friction and Wear Property of Aluminum, Intemational Joumal of Mechanical & Mechatronics Engineering IJMME- IJENS Vol, 11 No. 01 (2011), 45-49;
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4. Grudzuiski K., Kostek R., Influence Of Normal Micro-Vibrations In Contact On Sliding Motion Of Solid Body, Joumal Of Theoretical And Applied Mechanics, 43, 1, Pp, 37-49, 2005;
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Tribology Intemational 37 (2004), 833-40, 8. Littmann W, Storck H, Wallaschek J, Sliding Friction In The Presence Of Ultrasonic Oscillations: Superposition Of Longitudinal Oscillations. Arch Appl Mech 2001;71:549-54.
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Smdy on use of vibration to reduce soil adhesion, Joumal ofTerramechanics 35 (1998) 87-101;
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£., and Kapoor S. G., Modeling Chip-Evacuation S U M M A R Y
E M P L O Y T H E E F F E C T OF F R I C T I O N R E D U C T I O N IN V I B R A T I O N A S S I S T E D M A C H I N I N G
Nguyen Van Du'*, Chu Ngoc Hung', Ho Huu Duc^
'College ofTechnology - TNU
^Vietnam - Korea Vocational College, Vinh, Nge An This paper presents experimental results to evaluate the effect of vibration in sliding direction on friction reduction. Vibration along the sliding velocity was then employed in ultrasonic assisted driltuig. Statistical experiments showed that, friction torque when drilling can be reduced by 30 percents. The effect of friction reduction can enhance chip evacuation capacity, reduce drilling torque so as to reduce cuttmg temperature and thus increase the tool life. The experimental results lay a basic for fljrther development of general theoretical models.
Keywords: Friction effect, vibration, vibration assist, sliding velocity, ultrasonic vibration
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