B CNG THNGTRNG I HC CNG NGHIP TP. HCMKHOA C KH

N TT NGHIPTHIT K TI U,M PHNG PHANH LU CHT T BIN

GVHD:TS.Nguyn Quc HngNhm Th:Nhm 5

TP. H Ch Minh, thng 4 nm 2013

DANH SCH NHM(DHCK7BLT)01. Nguyn Vn Lm 1129862102. Nguyn Vn Hng 1129861103. Nguyn Mnh Hng1128244104. An Minh Lun 1128985105. inh Thanh Hoi1131747106. Phm Huy Phc1128312107. inh Thnh Nam1129774108. Nguyn Vn To1129788109. Nguyn nh Lng11283121010. Nguyn Phng Nam11293501

NI DUNGI. Tm hiu v lu cht t bin v ng dng.1. Gii thiu chung.2. Cc nguyn tc c bn v ng dng ca MRF.2.1 Kt cu cu ca MRF.2.2 T tnh ca MRF.2.3 Cc tnh cht c bn ca lu cht t bin.2.4 Bin i ca lu cht trong MRF.3. Hot ng ca cc ch trong MRF v ng dng ca n.4. Phng php thit k ti u ca MRF- cc chi tit c bn.4.1 Mt s chi tit c bn ca MRF.4.2 Vn ti u ha trong thit k c s ca MRF.4.3 Thit k ti u MRF da trn phn t hu hn.5.Nghin cu thit k ti u Van lu cht MRF.5.1 Hnh dng v m hnh ca van lu cht.5.2 .S ti u ha ca cc van lu chttrong iu kin gim p lcvphm vi hot ng.6. Nghin cu thit k ti u xi-lanh ca b gim chn t bin.6.1. Hnh dng v cu to ca b gim chn t bin6.2. Ti u ho khong ng lc ca b gim chn t binII. Tm hiu v cc loi phanh lu cht t bin.1. Gii thiu chung2. Phanh lu cht t bin3. Thit k ti u phanh lu cht t bin

NHN XT CA GVHD................................

I.Tm hiu v lu cht t bin v ng dng.1. Gii thiuCht lng t lu bin (lu cht t bin) l th keo khng c cc ht t ha khong hng chc micron (20-50 micron) trn ng knh. Ni chung, lu cht t bin bao gm du, thng l khong vt hoc silicone c s , v thay i t l phn trm ca cc ht cha st c ph mt vt liu chng ng t. Khi khng cho hot ng , lu cht t bin th hin nh lut Newton-nh. Khi tip xc vi t trng, cc ht cha st c phn tn trong cht lng to thnh lng cc t. Nhng lng cc t xp thnh hng theo ng ca t thng. Cht lng c pht trin bi Jacob Rabinow ti Cc Tiu chun Quc gia Hoa K trong cui nhng nm 1940.Trong nhng nm u tin, c mt lot cc li ch trong MRF nhng li sut ny nhanh chng suy gim. Trong u nhng nm 1990 c s phc hi trong nghin cu lu cht t bin ch yu do nghin cu v pht trin ca Tng cng ty .Mc d trong hot ng tng t cho dch in lu bin (ERF) v ct thp cht lng, thit b MR c kh nng mnh nng sut cao hn nhiu khi c kch hot. i vi li th ny, nhiu c ch lu cht t bin da trn c pht trin nh MR van, MR phanh, MR ly hp, MR van ..., v by gi mt s trong s l thng mi. Cng-bit rng hiu sut ca h thng da trn lu cht t bin ph thuc ng k vo mch t kch hot, do , theo thit k ti u ca cc mch t kch hot, hiu sut ca h thng lu cht t bin da trn c th c ti u ha. Gn y, c nhiu nghin cu v thit k ti u ca cc thit b lu cht t bin da trn nh MR van iu tit, MR van, MR phanh. Kt qu t cc nghin cu cho thy rng hiu sut ca h thng lu cht t bin da trn c th c ci thin ng k thng qua thit k ti u ca mch t ca h thng.Do , chng ny tp trung vo cc phng php thit k ti u ca cc thit b da trn lu cht t bin. Chng trnh c t chc nh sau: Sau khi gii thiu cc chng, nguyn tc c bn ca lu cht t bin , l thuyt ng sau lu cht t bin. Phn 3 cp n cc phng thc c s dng trong cc thit b da trn lu cht t bin v cc thit b khc nhau c tnh nng lu cht t bin c tho lun. Trong phn th t, phng php thit k ti u ca c ch lu cht tbin da trn c xem xt. Trong phn ny, trc ht l s cn thit phi thit k ti u ca cng ngh s c tho lun. Sau cc mch phn tch t tnh v cc mhnh ca cc thit b lu cht t bin c xem xt. Ngoi ra, cc vn ti u ha cc thit b lu cht t bin c tm ra v cc phng php gii quyt vn c iu tra. Phn 5,6 v 7 c dnh cho vic gii quyt vi cc nghin cu trng hp cho thit k ti u in hnh lu cht t bin cc thit b da trn nh MR van, van iu tit MR v MR phanh tng ng.

2.Cc nguyn tc c bn v ng dng ca MRF2.1 Kt cu ca MRF.Thng thng MRF gm nhng cht lng c nhng ht cht rn nh khng dnh nhau li ti l lng trong ,c t tnh,cc hp cht v nguyn t nghch t trong mi trng khng t tnh.Thc t MRF gm nhng ht t ha c nh nh st,hp kimst, oxit st, nitrit st, stcacbua, stcacbonyl, niken v coban.Trong s nhng ht ny,ht c p ng t tnh thch hp thng c dng nhiu cho vic hnh thnh nn MRF l st cacbonyl.ng sut chy ti a c th c to ra bi hiu ng ca MR ch yu c xc nh da trn khng t thp v mc cao nht ca t ha bo ho ca cc ht phn tn.Do nhng vt liu c t tnh mm vi tinh khit cao nh bt st cacbonyl l thnh phn chnh to nn cu trc thc t ca MRF. Khchnstcacbonyl, Fe-Co hp kimvhp kimFe-Ni cng c thc s dng nhvt liuMR, theo , Fegp phn vo vict habo hacao. Ngc li,mt s vt liut tnh nhMn-Zn ferrite, Ni-Zn ferritevferrites c t ha bo ha thp v do thch hp trong vic ng dng trong cc ng dng ca ng sut chy thp.Ht MR thng rt nh khong 0.1-10m nhng m ln hn khong 1000 ln so vi nhng ht khc trong dung dch st t.Trong MRF cc ht t tnh nm trong mt vng phn b nht nh m c th cung cp mt phn th tch ti a m khng lm nht trong vng zero tng mt cch khng th chp nhn c.V d thnh phn cht lng m c 50% th tch bt st cacbonyl c ng dng trong vic iu khin moment xon trong lnh vc in c.

Cht lng c cha ht ti in to nn mt qu trnh lin tc ca MRF.V d mt s cht lng tng thch gm nh du silicon, du khong, du paraffindu trng, du thy lc, du bin p,dung dch hu c halogen ,diester, polyoxyalkylene, xilicon flo ha ,glycon, ncv cc loi duhydrocarbontng hp.S kt hp ca cc dung dch ny c th c s dung nh l thnh phn ht ti in ca MRF.

Cht hot tnh b mt,ht nano,ht nano t ha,hoc nhng ht c ph t tnh c th c thm vo lm gim s kt ta ca cc ht nng trong giai on cn dung dch.Hin tng kt ta c th gy ra s trt dnh mng ca cht huyn ph.Vi s kt ta nhiu hn,MRF s chu nh hng di p lc v tc trt cao hn trong thi gian di ,dung dch s dn c c li.Hin tng kt ta s lm gim s nh hng ca MR ni m nhng ht trong MRF ong cng li v hnh thnh nn mt khi cng ni m gm nhng ht c bn c lin kt n nh do vic hnh thnh nhng dy khng hon chnh.Vt liu c th ngn s kt ta nh st hu c lm cho s kt ta tr nn mm hn. Khi cc thnh phncaMRFc nhttng i thp, n s khng ng cng v d dng.Vic ph mt lp polymer cng nh hng n tnh cht t tnh ca cc ht v lm cho chng d dng ti phn tn sau khi t trng khng cn na.Tuy nhin,tnh cht c trng ca MRF nh lc trt ,ng sut chy trong cng iu kin s chc chn suy gim bng cch thm lp ph vo.Do s che chn ca cc lp polimer m nh hng n tnh cht t tnh ca cc ht.Ngoi ra mt s cht ph gia c th ci thin mt s tnh cht ph nh n nh oxy hahocchu mi mn.2.2 T tnh ca MRFCc thuc tnht tnhtnh caMRFrt quan trng thit kcc thit bMRF v thng thng c c trng bi tnh t tr ca B-H & M-H. Thng quacc thuc tnht tnh,s ph thuc ca MRF c th c d on nh vo cc thit b.Di nh hng ca t trng ,mt m hnh chun cho cu trc thng c s dng d on nh hng ca nhng ht trong RMF.M hnh ny da trn mt mng li hnh khi c v s dy ht sp xp theo mt ng thng tng ng vi hng ca t trng c th hin hnh 1.

M hnh m t s bin i afin ca mt chui ht hnh cu.Cc chui ny c xem nh l s bin i ca cng khong cch gia hai ht gn nhau trong mt chui v tng cng mt t l khi MRF bin i.Trong trng hp thc t , kt cu ny kh n gin khi cc chui c hnh thnh nn lin kt nhiu khi cu cht ch m c cu to di dng hnh tr.Di ng sut ,cc lin kt ny c th bin i v cui cng b ph v. Mc dcc htpht trin thnhcu trc phc tpkhc nhautrong cc iu kinkhc nhau,kt cu ny vn c th cho bit ng sut chy din ra nh th no. Ccphng trnh chuyn ngcami httheo t trngl cn thit nh gi c tnh dung tch ca RMF. Ti mtt trngrtthp,ten x lc t Fij c tnh c khi im lng cc tng tc tng cp vi nhau, moment lng cc tgy rabi cc htkhcv cc bc tngxung quanh cho cc khi cu cch in hoc khng t tnh di mt t trng c tnh:

Fij l ten sor lc t tc dng ln ht i t ht j,p : dn t ca ht,0: dn t chn khng ca ht, v tr t ht j n I v m l mo ment lng cc t c gy ra bi cc ht trong MRF:

H: l t trng iu, a: l ng knh ca ht v c tnh:

dn t ring ca dung dch ti in. t trng cao ln ca mo ment lc t xem nh l im lng cc t c lp khi t tnh ca ht t bo ha.Trong trng hp ny moment lng cc t c tnh :

sMslt habo ha caccht, l khong1,7x106A/mchokhi stv0.48x106A/mcho xit st t.

2.3. Cc nguyn tt c bn ca tnh cht lu bin:Lu bin hc l mt ngnh ca c hc nghin cu bin dng ca vt liu . Lu bin hc lmtlnh vc lin ngnhv c s dng m tcc c tnh canhiu loi vt liunh du m,thc phm, mc in, polyme, t st, b tng, nha ng.Cc thng s v i lng ca lu bin c th c dng xc nh nh hng ca vt liu phi Newton, vt liu n hi nh l mt hm ca thi gian.Mc n nh ca hm khi ng yn hoc trong sut qu trnh lu chuyn, nht trt bng 0,hoc nht ti a ca dng cht lng ngn chn s kt ta.Cng thc nht da trn c s l thuyt thy lc ng hc cho s phn tn long ca nhng ht hnh cu c tm ra bi Einstein khong 100 nm cch y .Cng thc c suy ra t:

: l nht tng i cht huyn ph

: l phn khi lng cht ha tan ni l lng hoc ht ging hnh cu.

Vic thm cc ht rn vo dung dch lm tng lngca cc htv do lm tngt lkhi lngca cc ht.Khi th tch ca cc ht tng ln, nht tng ln .Sook cho rng nng ti a ca cc ht nn c kt hp trong mi lin quan gia nht v nng .

Tuy nhin nhng cng thc ny khng ph thuc vo hnh dng v cng ca ht Do , TodavFurusem rng cng thc cho thy kch tht ca cc ht nh hng n nht nh th no

lh s hiu chnhc thph thuc vokch thcv mt ca cc ht. nht cacht lng c thc tng ln vis lngb sung cacc ht rn. Tuy nhin, cng lc ,tnh cht ca cht lng s thay i v phn ra t cht lng Newton Ni chung, ng sut cttngvitc ctdy/duthng c thc c trng biccmi quan h.

y, v nl hng s,ylng sutvl nht ng.

Cht lng Newton xay ra khi cc dng cht lng khng c ng xut chy hoc y bng 0 v n bng 1. nht ca cht lng Newton khng ph thuc vo thi gian v tc ct. Hnh2 cho thyvic phn loicht lngda trn tnh chtlu bin.Nh th hin trong hnh,tnh cht ca cht lng c th c chia thnh cht lng Newton v cht lng phi Newton nh nha,Binghamnha, cht lngginhavcht lng gin n c. Cht lngc cho lnhakhing sut ctphi tmt gi trti thiu no trc khi nbt u tun chy.Nu vt liu l nha Bingham th n=1 .Cht lu gi do hoc cht lu trt dnh mng nht ng lc gim khi tc ct cao .Cht lng trt ng dy hoc cht lng gin n th ngc li, nht ng hc tng khi tc ct tng .Cht lng trt ng dy n>1,cht lng trt dnh mng n1: cht lng trt mng,m tp tin ghi nhn s kin (log file) thc n con t thc n gia ca phn mm ANSYS. a vo gia phn tch, DVs nm mc c dng lm bin s tng trng cho v gi tr khi u c phn cng cho h. Ni chung, tnh thc hin c c im ca thit b, mt t thng qua th tch hot ng ca MRF nn tnh. Mt t thng (B) v cng t trng ( H ) khng l hng s dc ng MRF, cho nn s trung bnh nn c s dng. S trung bnh mt t thng v cng qua ng l tnh bng cch ly tch phn mt thng lng dc ng xc nh trc, sau chia cho di ng i [ 79, 80 ]. tnh hng s thi gian quy np, th nht t thng l nh nh sau :

B(s) l mt t thng mi im nt trn ng, s l bin s gi cho ly tch phn. Ly tch phn c thc hin dc di ng iLp. c bit l kch thc hnh hc ca thit b MRF i trong quy trnh ti u ha, sao cho n khp ca c kiu FE nn c quy nh bi s ca phn t mi ng ch khng phi l c phn t. Sau khi gia phn tch c chun b, phng php t c tham s thit k ti u ca thit b MRF s dng phng php dy u tin ca dng c ti u ha ANSYS c hnh ng nh c trnh by trong Hnh 9. Khi ng vi gi tr khi u ca DVs, bng cch thc thi gia phn tch, gi tr khi u ca thc hin c c im ca thit b nh l nng lng iu khin, hng s thi gian quy np, st p sut, lm gim lc, mmen hm v truyn mmen c t c. Chng trnh ang np d liu...Lm n ch mt lc ri dch li !Khng chiu, khng b gii hn hm mc tiu c trnh by nh sau :

OBJ0 l gi tr hm mc tiu tham kho c chn la t nhm dng ca b my bn v phc, q l tham s mt p li m iu khin tho mn bt p.Px l hm hnh pht ngoi p dng cho bn v phc bin s x. Pg l ko di - phn trong hnh pht hm p dng cho trng thi bin s (bt p) g. Cho php lp u tin ( j = 0 ), hng nghin cu ca DVs l gi c i lng m ca graien ca hm mc tiu khng b gii hn. Do , vect hng l tnh bng

Tiu chun ca DVs a vo php lp ti ( j + 1 ) thu c t cn bng i theo,

u sj tham s nghin cu ng l tnh bng cch s dng k thut kt hp ca thut ton t l iu ho v lp phng trnh bc hai a phng. Cc tp tin phn tch sau c thc thi vi tiu chun tin ca DVs v tnh hi t ca hm mc tiu, OBJ, c kim tra.Nu tnh hi t xy ra, tiu chun ca DVs ti php lp jth l iu kin ti u. Nu khng, php lp tip theo s c thc hin. a vo php lp tip theo, phng php ging nhng ca php lp u tin ngoi tr vect hng y c tnh theo cng thc s quay tr li Polak-Ribiere nh sau :

Do , mi php lp c to thnh t mt s nhm - php lp bao gm nghin cu hng v graien tnh ton. N c lu phn mm ANSYS gi ta bi ton bn v phc ti u bng cch ly tch phn dng c ti u ha. Do , trong hu ht cc trng hp dung dch ti u ca thit b c s MRF c th gii trc tip bng phn mm ANSYS khng c mt phn cch vi bt k phn mm lp trnh. s dng dng c ti u ha ANSYS, cn phi thit lp tham s ti u ha. lm c iu ny, th nht tp hp phn tch nn bng tay thc thi mt ln ti tt c tham s a vo tp hp phn tch vo b nh m phn mm. Sau , t thc n Chn Bn v phc, chng ti nh r gia phn tch m s c dng trong quy trnh ti u ha, DVs vi gii hn v chp nhn ca h, bin s trng thi ( nu c ) vi gii hn v chp nhn, hm mc tiu vi tiu chun tnh hi t, phng php cho gii dung dch ti u, v quyn la chn kim sot u ra ti u nu cn. Trong mt vi trng hp, n phi s dng mt s thut ton ti u ha tin tin nh l Thut ton Di truyn, Li Dy thn kinh, hoc thut ton nh r ngi s dng, mt phn cch gia ANSYS v phn mm khc thc hin ti u ha nh l Matlab, Fortran, ngn ng C bt buc.

5. Nghin cu thit k ti u ca van lu cht(MR).

5.1. Hnh dng v m hnh ca van lu cht.

Hnh 10 cho thy cc cu trc ca hai loi in hnh ca van lu cht: van lu cht hnh khuyn (Hnh 10a) v van lu cht vi ng dn dng chy c hnh khuyn v xuyn tm (Hnh 10b). Cc thng s trong (hnh 10a)bao gm cun dy van, li v v. Dng lu cht chy qua ng dn hnh khuyn gia li A v B. Khi trong li xut hin dng in, mt t trng c tc dng ln dng lu cht, lc dng lu cht chy qua cc ng dn thay i trng thi ca n vo bn lng hoc dng rn v ngn chn dng chy. Ch khi p lc cung cp c cao b p ng sut, cht lng c th chy qua van mt ln na. Cc thng s trong hnh 10b bao gm cc li van, a t v bung vanto thnh mt mch t ca van. Mt vng m khng t tnh c s dng m bo dy cn thit ca ng knh. Khi a t tnh c t ng trc vi bung van bng cch s dng np hnh nn, cc ng dn hnh khuyn v xuyn tm c hnh thnh gia cc a v cc bung van, v a v li van, tng ng. Dng lu cht chy t u vo thng qua cc ng hnh khuyn v xuyn tm u tin, sau dng chy dc theo l trung tm ca li v sau theo ng dn xuyn tm v vnh khuyn th hai vo cm.

Hnh 11a cho thy mt cu trc n gin v ngha kch thc ca mt van lu cht hnh khuyn n cun. Dng hnh hc van c c trng bi chiu di tng th L, bn knh bn ngoi R, dy bung van th, khong cch khe h ca van lu cht tg, mt bch li (cc) dy tfv chiu rng cun dy wc. Bng cch s dng m hnh nha Bingham, p sut ca van c tnh bng [80, 81]:

y v l phm vi ph thuc v p sut chy nht ca van lu cht hnh khuyn n,

l tc dng chy qua van MR. Cun cun dy van

Rd l bn knh trung bnh ca ng hnh khuyn c a ra bi:

c l h s ph thuc vo dng i ca vn tc dng chy v c tm gi tr t mt gi trti thiu2.0 (cho ln hn 100) mt gi tr ti a3.0 (t hn 1).

Van lu cht a cun.ci m ln u tin cs dng biSpencerv cng s ca ng. thc hin mtgim chnlcMRvan iu titcaoc s dng trongh thng bo va chn[85], by gi cs dng rng ritrongnhiu ng dng.ChovanMRvihaicun dy, p sut gimc tnh bng:

Vi P2A,v P2A, l phm vi ph thuc v p sut chy nht ca van lu cht hnh khuyn hai cun dy.

v l ng sut dng chy lu cht cui v gia ng dn.c1 v c2 l h s ph thuc vo hnh dng vn tc dng chy ca lu lng lu cht cui v gia ng dn.Tng t nh vy, i vi ccvan lu cht hnh khuyn ba cun dy,p sut gimc tnh bng:

Vi P3A,v P3A, l phm vi ph thuc v p sut chy nht ca van lu cht hnh khuyn ba cun dy.ChovanMRvi ng dndng chychnh khuynvxuyn tmth hin trong hnh11b, p sut gimc th ctnh bng:

PAR,v PAR,l phm vi ph thuc v p sut chy nht ca van c th c tnh bng:

vl ng sut gy ra trong ng hnh khuyn v ng xuyn tm ca dng luu cht.R0 l bn knh ca l tm ca li van v R2 l bn knh ngoi ca ng dn xuyn tm. y, Ca v Cr l cc h s ph thuc vo hnh dng vn tc ca dng lu cht chy qua cc ng dn hnh khuyn v xuyn tm, tng ng.5.2.S ti u ha ca cc van lu chttrong iu kin gim p lcvphm vi hot ng.

Mc tiuti ul nhm gim thiut svanc xc nhbng t sphm vi ph thuc v p sut chy nht. T l nycnh hng ln ncc c tnh cavanlu cht. l mong mun rng t s van c gi tr nh. Cc van thng b hn ch trong mt hnh tr c bn knh R = 30mm v chiu cao H = 50mm. Tnh cht t ca cc thnh phn van c cho trong bng 1. nht sau bin dng ti gii hn chy ca MRF c gi nh l khng i, = 0.092Pa.s v tc dng chy ca van l . Cht lng lu cht (MRF132-DG) t Tng cng ty Lor c s dng. p lc gy ra do nng sut ca cht lng MR nh mt chc nng ca cng t trng p dng (HMR) c th c th hin bng khong:

Trongphng trnh. (42),cc n v cang sutlkPatrong khi cng t trnglkA /m. Cc h sC0, C1,C2, v C3, c xc nh tkt qu thc nghimbng cch p dngccng congvungphng phpph hpnht, cxc nhtng ngl0,3, 0,42, -0,00116v1.05E-6.Cn lu rng, mt s thay inhtrongccvan thkhong cchtgslm thay ing khiu sutca vanMR. V vy, trongMRthit kvan, mt khong cchc nh cla chn theotng ng dng.Trong nghin cu ny, khong cch vanc chn l1mm. TEQS. (36)-(41),t lvancan cun, haicun dyvvanMRxuyn tmhnh khuynctng ngtnh theo:

Thnh phn ca vanVt liuKh nng thm tng iMt t thng bo ha

Li vanThp silicon20001.45 Tesla

Bung vanThp silicon20001.45 Tesla

Cun dyng1x

Cht lng lu chtMRF132-DGng cong BH1.6 Tesla

Khng tCp/CunKhng c t tnhthp1x

Hnh 1: Tnh cht t tnh ca cc thnh phn van.

Hnh12acho thy ccgii phpti u ca mtvan lu cht hnh khuyn n cun rng bucv khi lng nht nh khimtdng in 2.5Ac p dng chocc cun dyvan. Gi tr ban uca t,wcv th thl17mm, 10mmv6,5 mm, tng ng. T svan, p sutgim vtiu th in nngcaccvannhnggi tr ban ul , v.Tcon s ny, n cquan st thy rngccgii phphi tsau13ln lp livgi tr ti thiut lvan(hm mc tiu) l . p sut gimtng ngl , cng lmc ti a.Ti u nht, tiu th in nnglnh hnban unhiu. DVStithi imti u l , , . Hnh12bcho thy ccgii php ti ucavan lu cht hnh khuyn 2 cun dy. Gi tr ban ut, wcv thl10mm, 5mm, 10mmv4mm, tng ng. T lvan, p sutgim vin nng tiu thcc gi trban ul , v N0=83.2W, tng ng. Gii php lhi tsau11ln lp livgi tr ti thiut lvan l . p sut gimtng ngl , cng lmc ti a.DVSti ul, , v .

Hnh 12: S ti u ha ca cc van lu chttrong iu kin gim p lcvphm vi hot ng.Hnh 12c cho thy cc gii php ti u ha ca van lu cht vi dng chy xuyn tm.

Gi tr ban u ca R0, t, wc v th l 6mm, 10mm, 6mm v 8mm, tng ng. T s van, p sut gim v in nng tiu th cc gi tr ban u l 0 = 0,041, P0 = 47bar v N0 = 44.3W, tng ng. S hi t xy ra 10 lp li, m ti gi tr ti thiu t l van l OPT = 0,023 v cc thng s thit k ti u l , , v. p sut gim tng ng l POPT = 37.2bar, m khng phi l gim p lc ti a. L do ca vic ny l s st gim p lc khng kim sot c (gim p sut nht) ca van ph thuc ng k vo bn knh li van. S gia tng ca van li kt qu bn knh trong gim p sut gim nht m lm gim t l van. Tuy nhin, s gia tng ca bn knh li van lm gim mt t thng, v do lm gim gim p lc ca van. ci thin hiu sut van, bn knh li van nn c c nh mt thch hp. Trong trng hp bn knh li van c c nh 6mm, n c tm thy rng gi tr ti u ca van t l l OPT = 0,0293 v p sut gim tng ng l POPT = 64.4bar, cng l mc ti a. DVS ti u l tOPT = 8.6mm, v . Ti cc DVS ti u in nng tiu th l N0 = 29.1W.

Bng 2 tm tt cc kt qu ti u ha cho MR thit k van nu trn. Kt qu cho thy hnh dng hnh hc ca MR van c mt nh hng ln n hiu sut van. Bng cch la chn mt hnh dng ti u, hiu sut nh van gim p sut c th c ci thin nhiu v tiu th in nng c th c gim ng k. Trong s cc van MR hn ch trong cng mt khi lng, hai cun dy hnh khuyn MR van cung cp gi tr tt nht ca t l van trong khi cc hnh khuyn-xuyn tm c th cung cp gim p lc tt nht vo cc thng s thit k ti u. Cho cc loi van MR vi ba cun dy tr ln, ngi ta thy rng hiu sut ca cc van khng phi l tt hn so vi cc van MR hai cun dy cc thng s thit k ti u.

Loi vanThng s thit k [mm]T s van, p sut gim & tiu hao nng lng

Ban uTi uBan uTi u

Van lu cht hnh khuyn n cunt = 17W= 10dh = 6.5t = 17.23W= 1.78dh = 7.43

N = 38.83[W]

N = 7.92[W]

Van lu cht hnh khuyn 2 cun dya=10t = 5W= 10dh = 4a=19.7t = 10.6W= 6.38dh = 5.33

N = 83.2[W]

N = 16.5[W]

Van lu cht hnh khuyn 3 cun dyb = 6a =7t = 7W= 10dh = 6b = 6.36a =10.94t = 5.84W=7.48dh = 3.35

N = 55[W]

N = 37.4[W]

Van lu cht vi dng chy xuyn tmt = 10W= 6dh = 8t = 8.6W= 3.1dh = 6.36

N = 44.3[W]

N = 29.1[W]

Bng 2: thng sthit k ti u ha cho van lu chtN cng c th hin bi ng Nguyn v cng s. [79] l gii php ti u b nh hng bi p dng cha hiu qu. p dng gi tr cao ca dng int hiu sut tt hn ca van. Tuy nhin, khi p dng tng hin ti mt gi tr nht nh cc gii php ti u c xu hng bo ha. Do , n c thng bo rng hin ti p dng phi c thit lp bi n gi tr ti a cho php trong cc vn ti u ha ca van MR.

6/ Nghin cu thit k ti u xi-lanh ca b gim chn t bin:6.1/ Hnh dng v cu to ca b gim chn t bin:Nghin cu ny ch n xi-lanh hnh tr trong b gim chn t bin ca cc xe d kin lp rp bi Lee va Choi c th hin trong hnh 13. B gim chn t bin c chia thnh bung trn v bung di bng pittong v y lu cht gia. Khi pit-tong di chuyn, dng lu cht trong gim chn t bin chuyn t bung nay sang bung cn li v i qua c hai u ca phn ng hnh vnh khn gia thnh ngai v thnh trong ca xi-lanh. Bung gas nm ngoi ng vai tr nh mt c-quy cha ng dng lu cht gy ra bi chuyn ng ca pit-tong

Hnh 13: Cu to ca b gim chn t binBng gi thit l b qua lc ma st gia du trong xi-lanh v cc trng thi ca gim chn iu trong iu kin l tng th lc gim chn ca b gim chn t bin c th c tnh bng cng thc:

(46)

Trong :

iu kin tin quyt cng thc (46) ng lc n hi ca gas phi ph hp. iu kin th hai l nht ca dng lu cht t bin. iu kin th ba l lc sinh ra do ng sut nn ca lu cht t bin, lc m c th c iu khin lin tc bng cng ca trng in t dc sut theo ung ng cha lu cht. Ba iu kin trn l i hi ch yu ca lc gim chn, lc m c k vng l t c gi tr ln khi thit k b gim chn t bin. Khong ng lc ca b gim chn (xc nh bng t s gia lc ln nht khi dng lu cht vo ln nht v lc khi dng lu cht vo bng 0) c th c tnh gn ng theo cng thc:

(47)

Khong ng lc cng l mt thng s quan trng trong vic nh gi ton b cht lng hp th chn ng ca lu ca gim chn t bin.Mt gi tr ln ca khong ng lc c k vng c cung cp bi mt khong iu khin rng ca b hp th chn ng trong gim chn t bin. Hn na, FMRmax l lc sinh ra do ng sut nn khi dng lu cht tc dng l ln nht. Ap v As tng ng l tit din pit-tong v tit din ca trc pit-tong. xp l chuyn v ca pit-tong. L l chiu di ca thnh trong xi-lanh.tg l h ca ng ng gia thnh trong v thnh ngoi xi-lanh. R1 v R2 tng ng l bn knh trung bnh ca nam chm v bn knh ca ng ng.Lm l chiu di ca nam chm in t.tm l khe h gia trc pit-tong v van iu tit.c l h s ph thuc vo dng vn tc dng chy ( c c gi tr nh nht l 2,07 n gi tr ln nht l 3,07). Pa l p sut trong bung gas v c xc nh bng cng thc:

(48)Trong :P0: l p sut ban u ca bung gas.V0: l th tch ban u ca bung gas. : l h s gin nhit trong qu trnh on nhit ( 1,4 1,7).

6.2/ Ti u ho khong ng lc ca b gim chn t bin:Trong phn ny, Phng Php Phn T Hu Hn c tch hp vo mt phn mm ti u ho c dng tnh ton kch tht hnh hc ti u cho b gim chn t bin vi yu cu tho mt hm cc tiu cho trc. thit k h thng gim xc cho xe chy nh v khng xc (khng gian Rattle) l hai c tnh i nghch c quan tm. Trong yu cu gim bt cc chn ng khi di chuyn th lc gim xc i hi phi cao.Theo mt cch khc, tng s m nh khi chy th lc gim xc nh c k vng.y l khong ng lc ln c mong i.Ngoi ra, thi gian p ng nhanh ca b gim chn t bin cng c mong i trong yu cu nng cao kh nng iu khin ca h thng gim xc. Ni n mt yu cu cao hn trong tnh ton, ta tnh theo hm mc tiu d kin l:

(49)

Trong :FMR: l lc sinh ra do ng sut nn.d: l khong ng lc.T: l hng s thi gian cm in ( hng s ny quy nh r trn dung dch FE ca mch t gim chn).FMR,r; d,r; Tr: tng ng l cc thng s chun ca lc sinh ra do ng sut nn, khong ng lc v hng s thi gian cm in.F; d; T: tng ng l ch s khi lng ca lc gim chn, ch s khong ng lc v ch s thi gian cm in (F + d + T = 1).iu quan trng l gi tr ch s khi lng c chn ph thuc vo c trng ring ca mi h thng gim xc.i vi h thng gim xc c thit k cho phng tin i trn ng khng bng phng hoc ng khng c tri nha th lc gim xc ln l cn thit. Nh vy, trong trng hp ny ta chn gi tr F v T. Cn gi tr d c dng trong thit k h thng gim xc cho ng bng phng.Lc gim xc tiu chun, khong ng lc v hng s thi gian cm in ca b gim chn t c t cc gii php ca b gim chn t bin ti cc gi tr ban u ca cc thng s thit k. Cc kch tht hnh hc ban u ca b gim chn da trn gi thit ca mt t thng khng i trong mch t ca cc b gim chn. Vy, gi tr bn knh ban u ca li l Rc, rng ca cun dy l wc. B dy v ca van c xc nh nh sau:

Trong :Rv: l bn knh ngoi ca vanGi tr di ban u ca nam chm Lm c xc nh sao cho mt t thng khng vt qu gi tr bo ho ca vt liu lm li van (thp silic) l 1,5 Tesla trong nghin cu ny.Hnh 14 th hin gn ng mch t ca kt cu van t vo trong b gim chn. Khi t trng thp, t biu thc (20) ta thy cng t trng qua th tch hot ng ca lu cht t bin c th c tnh gn ng theo cng thc:

Mc dn t ca lu cht t bin phi nh hn ca vt liu lm li. Biu thc (51) c th c tnh tng ng bng Hmr = NcI/2tm. Trong trng hp ny, p ng c s bo ho ca vt liu lm li th phi tho mn iu kin sau y:

Hnh 14: Mch t gn ng ca b gim chn t binTrong phn ny, thp silic (thp c t tnh c th hin trong hnh 15a) c dng cho cc li ca van.T tnh ca lu cht t bin c th hin trong hnh 15b. Gi s hiu sut nht ca lu cht t bin l mt hng s, =0,0092 Pa.s v vn tc ca pit-tong c ti u ho l 0,4 m/s. Cc kch tht quan trng ca b gim chn t bin nh b rng cun dy wc, b dy lp v ca van th, h trc pit-tong v van kt cu tm, chiu di Lm ca nam chm c dng nh nhng bin s thit k. ng ch l tit din ca trc pit-tong c gi nguyn (Rs = 6mm) trong qu trnh ti u ho. Tuy nhin, tit din pit-tong c thay i tu thuc vo cc bin thit k (Ap = Rp2 ; Rp = Rv - th -tm - tin) Dy qun ca cun dy c kch tht bng 24 gauge (d = 0, 5106mm) v chu c dng in ti a cho php l I = 2,4A. Da trn mc s dng rng ri ca gim chn t bin, gi tr ban u ca l t bin c chn l tm = 0,75mm. T cc biu thc (50), (52) vi gi nh rng mt t tnh ca thp silic v lu cht t bin tng t l vi cng t trng = 2000, mr = 4. Gi tr ban u ca cc bin thit k c xc nh nh sau: Lm = 7,5mm ; wc = 2,4mm ; th = 5,6mm.

(a) B-H ng cong c tnh ca thp silic(b) B-H ng cong c tnh ca lu cht t bin

Hnh 15:c im t tnh ca thp silic v lu cht t bin

Bng 3 cho ta thy cc gii php ti u ca cc gim chn t bin vi cc b gi tr khc nhau ca cc h s gia trng ph thssuc vo mc tiu thit k.N c th hin t cc kt qu bng cch dng cc gi tr khc nhau ca h s gia trng trong kt qu ti u c th t c.Trong iu kin c gi tr ln, h s gia trng tr nn ni tri.

Thng sGi tr ban uGi tr ti u

F= d = T =1/3F= 0.5; d =0.2; T =0.3F= 0.2; d =0.5; T =0.3

h ca van tmChiu di nam chm LmChiu rng cun dy wcChiu dy thnh v thLc do ng sut nnKhong ng lcHng s thi gianHm mc tiuNng lng tiu th0.75mm7.5mm2.4mm5.6mm2065N8.8550.5ms18W1.1mm11.7mm3mm4.05mm1715N35.6440.6ms0.9436.21W0.81mm12.26mm2.72mm4.17mm2630N2042.3ms0.9375.16W1.47mm11.5mm3.3mm4.1mm1170N6340.3m0.8266.6W

Bng 3: thng s ti u ca phanh t bin loi a n

(a) Lc do ng sut nn gy ra(b) hng s thi gian cm inHnh 16: Lc do ng sut nn v hng s thi gian cm in trong ti u ho cc gim chn t bin ban u ti cc gi tr khc nhau ca dng lu cht. nh gi hiu sut ti u ca b gim chn t bin.Khong dng b tc dng, lc gim xc v hng s thi gian cm in ca cc b gim chn uc ti u ho ban u ti cc gi tr khc nhau ca dng lu cht trong hnh 16.Trong hnh ny, thut ng Opt.1, Opt.2, Opt.3 i din cho ba trng hp ti u trong bng 3. Tng ng nh sau: Opt.1: F = d = T = 1/3 Opt.2: F = 0,5 ; d = 0,2 ; T = 0.3 Opt.3: F = 0,2 ; d = 0,5 ; T = 0,3Cc thng s trn c xc nh t hnh m lc ca ng sut nn tip cn n mt mc bo ho khi dng in tc dng tng ln 1,5A. Hn na, ti gi tr dng in tc dng nh th h s thi gian cm in cng khng i. L do l ti dng in tc dng nh th t thng sinh ra nh. Vy mt t thng tng t l thn vi cng t trng. Ti gi tr dng in tc dng ln, mt t thng tip cn vi bo ho t tnh ca vt liu.iu ny dn n mt mc bo ho ca lc do ng sut nn v gim hng s thi gian cm in.

II.Tm hiu v cc loi phanh lu cht t bin.Nghin cu ny tp trung vo thit k ti u ca cc loi phanh lu cht t bin (MRB), t cc loi MRB ti u c chn.Trong vic ti u ha, loi ph bin ca MRB nh loi a, hnh trng, loi hn hp v loi hnh ch T c xem xt.Cc vn ti u ha l tm gi tr ti u kch thc hnh hc quan trng ca MRB c th to ra m-men xon phanh ti a. Cc MRB b gii hn trong mt th tch hnh tr c bn knh v chiu di c th. Sau khi m t ngn gn v cu hnh ca cc loi MRB, cc mmen xon phanh ca MRBs c ngun gc da trn Herschel Bulkley-m hnh ca cht lng MR. Thit k ti u ca MRBs b hn ch trong mt khi hnh tr c th sau c phn tch. Mc tiu ca vic ti u ha l ti a ha cc m-men xon phanh trong khi t s m-men xon (t s ln nht m-men xon phanh v moment ma st khi khng c t trng) c gii hn n gi tr nht nh ln hn.Phn tch phn t hu hn tch hp vi mt cng c ti u ha c s dng m phng ti u ti u MRBs. Da trn cc phng php ti u ha c xut, m phng ti uu MRBs thu c bi hn ch vi khi lng khc nhau. T cc kt qu vic la chn ti u ca cc loi MRB ty thuc vo khi lng gii hn c a ra.1. Gii thiuLu cht t bin (MRF) l gm cc ht cc ht l lng, c th b t ha , v nhng bin i nhanh chng, mnh m, v hi phc nh tnh cht lu bin ca n khi t trng c t vo. V vy, MRF c tim nng ln trong nhiu ng dng i hi lp trung gian in nh b ly hp, phanh, van,b gim chn v robot . c mt s lng ln cc nghin cu v pht trin ca phanh MRF trong nhiu ng dng. Loi phanh a l thit k ph bin nht v cng l phanh u tin c m t trong nghin cu v sau ca Rabinow, 1951 .y l loi MRB l rt d dng sn xut v cho kt qu kh tt v trng lng v nh gn. Thit k ny l ch c mt nhng rt c gi tr trong thng mi v l sn phm mu c sn xut bi LORD Corporation v c s dng trong nhiu nghin cu. Tuy nhin, trong mt s ng dng, phn s dng MRB l mt hnh tr nh v di. Trong trng hp ny, cc MRB kiu a l khng ph hp v phanh MRB kiu hnh trng s cho mt m-men xon phanh cao hn. Huang et al.,cung cp cho mt s cc biu thc gii tch m hng dn thit k v LORD Corporation s dng n nh mt mu c sn hng dn v thit k ca cc thit b lm vic s dng lu cht MR. Thit k hnh trng c c trng bi mt lc qun tnh ln m lm cho hnh trng o ngc li. Lc qun tnh ny cng c th c gim li nh hnh li mt phn bn trong ca n khi c t thng thp .Thit k trng ngc c s dng trong mt lot cc ng dng nh khp ly hp 40nm cho cnh qut xe ti c v pht trin bi General Motors hoc phanh trong bnh c s dng trong thit b tp th dc c bp. ci thin hiu sut phanh ca trng loi MRB, MRB vi roto hnh ch T c xem xt. Cc phanh rotor hnh ch T l nh gn hn so vi thit k trng, nhng phc tp hn sn xut (do cc di mng cc ca rotor).Mc d bn cao nhng thit k ny khng ph bin lm. Gn y, Nguyn el al. xut mt thit k kt hp ca MRB cho mt c tay haptic (c phn hi).Thit k ny l s kt hp ca phanh a v phanh trng .Trong nghin cu, thit k ti u phanh a, phanh hnh trng,kiu c phn hi, MRB c phn hi c thc hin. Kt qu cho thy thit kt kt hp ny cung cp mt hiu sut tt hn cho c tay my haptic hn nhng lai khc. Mc d c mt s lng ln cc nghin cu v thit k v ng dng ca MRBs v cc loi thit k c xut, s khc nhau v thit k ti u ca cc cu hnh ny vn cn thiu. ng gp chnh ca nghin cu ny l tp trung vo thit k ti u ca cc loi khc nhau ca MRB nhng gii trong mt khi lng c th. Mc tiu ca vic ti u ha l ti a ha phanh m-men xon ca MRBs. Cc phng php m phng ti u ca MRBs nhng vi mt khi lng nht nh thc hin v trnh by. T cc kt qu ny , mt la chn ti u ca MRBs c kho st.

2. Phanh lu cht t bin:Nh cp trn, loi u tin v ph bin nht ca MRBs l phanh a.

Hnh 1Hnh1 cho thy mt thit k in hnh ca MRB dng a .Rotor ca phanh l rt mng nhng vn gi l a quay.Khi mt dng in c t cho cc cun dy, mt t trng c to ra; MRF cui b mt ca a c in v tr thnh mt ng rn. Ma st trt gia a quay v MRF ong cng cung cp mt lc phanh lm chm dn v dng cc trc. Kch thc hnh hc quan trng ca MRB dng cng c hin th trong hnh. 1. Bng cch p dng cc tnh cht lu bin Herschel-Bulkley cho MRF, m-men xon phanh ca phanh loi a loi c th c xc nh bi :

,,Kd: tng ng l ng sut, h s tnh cht dng chy v c ca MRF cui b mt ng ca phanh.

: c gi l nht tng ng ca MRF trong ng ,K0: tng ng l ng sut, h s tnh cht dng chy v c ca MRF khi khng c t trng tc dng.

Bn knh ngoi v trong ca a.

Kch thc khe h ca vnh v b mt ng cui cng.

dy ca a.

Vn tc gc.Trong trng hp khng c in t vo cc cuc dy,m ment xon phanh c tnh:

eqd0 : nht tng ng ca MRF khi khng c t trng tc dng cui b mt ng.Tng t nh h thng phanh thng thng, bn cnh nhng MRB kiu a, MRB loi trng l mt trong nhng MRBs ph bin.

Hnh 2aHnh 2a cho thy mt hnh dng c trng v kch thc hnh hc c ngha ca MRB loi hnh trng. Trong trng hp ny, roto ca phanh l mt hnh tr di, v t trng c t vo theo hng xuyn tm. V bn ngoi ca phanh c lm bng vt liu khng t tnh nh vy khng c t trng tc dng dc trc c hai bn ca cc roto.Phanh loi trng, cc cun dy c qun trn mt cun c gia c trn lp v bn ngoi.iu ny gy kh khn trong sn xut ca phanh.Hn na, vi cc cun dy gn lin v bn ngoi, trnh dng t b nghn li, dy v bn ngoi phi ln.iu ny dn n kch thc ca phanh ln hn hoc m-men xon phanh nh (do bn knh ca roto nh). khc phc tnh trng ny, Phanh trng hnh.2b vi mt cun dy c t trn trng ca phanh.

Hnh 2bLoi MRB ny c ngc vi MRB hnh trng.Thit k hnh trng ngc ny c bic thch hp cho h thng phanh, trong trc ng yn trong khi lp v quay. i vi c hai loi phanh ny, m-men xon phanh v m-men khi khng c t trng tc dng c xc nh bng:

Ka: tng ng l ng sut, h s tnh cht dng chy v c ca MRF trong ng hnh khuyn ca phanh.Ro v Ri : l bn knh ngoi v trong cui b mt ngLa: chiu di lm vic ng hnh khuyn.La wd-wc. wd,wc:chiu rng ca trng v cun dy.eq0: nht tng ng ca MRF khi khng c t trng cui b mt ng.

.Nh nu trn, trong trng hp phanh kiu a, MRF cui b mt ca a s ha t. i vi phanh trng, t trng c t theo hng xuyn tm, do MRF bn ngoi mt tr ca ng s c in. Trong nhiu trng hp, c hai loi a u c s dng,nhng m nu kt hp c hai loi th cng c lu n.

Hnh 3aHnh 3a cho thy cu hnh hn hp ca phanh MRF. S khc bit duy nht gia phanh MRB loi kt hp v MRB kiu trng l v bn ngoi ca phanh kt hp l lp bn ngoi c lm bng cht liu t tnh.Do , t thng gy ra bi dng chy ca cun dy khng ch theo hng xuyn tm trn b mt hnh tr ca roto m cn theo hng dc trc ngang qua b mt cui cng ca roto.

Hnh 3Tng t nh phanh MRB hnh3a , mt cu hnh ngc kt hp c th hin trong Fig.3b c th c s dng khi cc trc ca phanh ng yn hoc trnh dng t b nghn li ti lp v hnh tr bn ngoi.M-men xon phanh v m-men xon khi khng c t trng tc dng ca phanh kt hp v phanh trng ngc c th c xc nh bi :

ye, ne v Ke: tng ng l ng sut, h s tnh cht dng chy v c ca MRF cui b mt ng ca phanh.

eq: nht tng ng ca MRF cui b mt ng.

c c mt mt t thng ng u hn phanh MRB, kiu kt hp vi hai cun dy qun ln vo hnh.4 c s dng.

Hnh 4a Tng t nh kiu kt hp li n, kiu hai cun dy bao gm :loi hai cun dy v loi hai cun dy o ngc qun li vi nhau ,tng ng hnh 4a,4b .

Hnh 4bi vi c hai trng hp, m-men xon phanh c th c xc nh bng:

Lah2 :chiu di lm vic ca ng hnh khuyn.Lah2 wd-2wc. wdv wc:chiu rng ca ng v cun dy tng ng.

Hnh 5 l kiu phanh ht hp hnh T. Bi v t thng ca MRB chy trn c bn trong ln bn ngoi ng hnh khuyn ca ca mt T v bn knh ng dn nhnh T, to ra m-men xon phanh mong mun.. M-men xon phanh loi kt hp hnh ch T c th c tnh nh sau:

Hnh 5

Tl, Ta1 v Ta2:tng ng l mmen xon phanh m bn ca nhnh T,bn trong v mt tr ngoi ca mt T v c xc nh nh sau:

Trong trng hp khng c in c t vo cc cun dy, m-men xon phanh c th c xc nh nh sau:

Ri :bn knh trong nhnh T.Rf, Ro: tng ng l bn knh trong v ngoi ca mt T.La1 and La2:chiu di lm vic bn trong v ngoi mt tr ca T.yl, ya1 and ya2 :tng ng l ng sut ca MRF trong ng nhnh T,bn trong v ngoi mt T.nl, na1, na2 : tng ng l h s tnh cht ca MRF trong nhnh T,bn trong v ngoi mt T.eql : nht tng ng ca MRF trong nhnh T.Kl, Ka1 v Ka2 : tng ng l c ca MRF trong nhnh T,bn trong v ngoi mt tr T.

3. Thit k ti u ca MRBTrong nghin cu ny, FEA tch hp vi mt cng c ti u c s dng c c kch thc hnh hc ti u ca MRBs nhng b hn ch bi mt khi lng nht nh.Mc tiu ca vic ti u ha l ti a ha cc m-men xon phanh.Ngoi ra, m-men xon khi khng c t trng c tnh n trong nghin cu ny nh l bin trng thi.Cn lu rng kch thc kch thc khe h ca ng MR cng nh th to ra m ment xon ln hn. Tuy nhin, khe h nh s to ra mo ment xon khi khng c t trng ln,iu ny lm gim cc c tnh ca MRBs nh nng lng tiu tn cao, ta nhit, di ng hc nh do lm gim hiu sut kim lm vic ca phanh. Trong nghin cu ny, t s m-men xon MRB - t s ca m-men xon phanh ti a v m-men xon phanh khng c t trng tc dng s ln hn gi tr mong mun. V vy, iu kin sau y phi c tha mn:

:t s mo ment xon ca MRB.cr :t s momeny xon ti hn.Tbmax :gi tr ln nht ca moment xon phanh ca MRBs.T0: moment xon phanh khi khng c t trng.Mment xon phanh ca MRBs (Tb) c xc nh bi phng trnh (1), (3), (5), (7) and (8) tng ng cho phanh a,phanh trng,phanh kt hp hai cun dy,v phanh loi T.Moment xon phanh khi khng c t trng tc dng c tnh bng phng trnh (2), (4), (6) v (12) tng ng cho phanh a,phanh trng,phanh kt hp (c n cun v hai cun dy) v phanh loi T.

Nh ni trn, trong nghin cu ny FEA tch hp vi mt cng c ti u ha c s dng c c m phng ti u ca MRB. Khi nim m phng ti u ca cc thit b MR thc hin bng cch s dng phng php bc nht vi cc thut ton tit din vng vi cc cng c ti u ca ANSYS c cp trong mt s chi tit trong qu trnh nghin cu. ng ch l, thay v ti a ha cc m-men xon phanh, ti u ha trong nghin cu ny gim thiu ha iu ny:Trc ht , xc nh m-men xon phanh ca MRBs mt t trn cc ng dn MR ca MRBs c tnh ton bng cch s dng FEA. Trong nghin cu ny, cc m hnh phn t hu hn s dng phn t i xng trc 2D ca hng phn mm ANSYS c s dng gii quyt cc dng t ca MRBs. Cc m hnh phn t hu hn c s dng gii quyt cc dng t ca MRBs c hin th trong hnh. 6, 7 v 8.

4. Kt qu v tho lunTrong nghin cu ny, ngi ta cho rng rotor v stator ca MRBs c lm bng thp silic, cc dy cun dy c o bng dng (ng knh = 0.511mm) m c dng in nh mc l 3A. Nghin cu ny xem xt hai loi ph bin nht ca MRF c thc hin bi Lord Corporation: MRF-132-DG (ng sut trung bnh) v MRF-140CG (ng sut cao). Tnh cht lu bin ca MRFs c th c c tnh bng phng trnh sau y:

Trong Y l vit tt ca mt thng s lu bin ca MRF nh ng sut chy, nht, c v tnh cht c dng cht lu. Gi tr ca tham s Y c xu hng Y0(khi khng c t trng tc dng) n gi tr bo ha.l h s m ment bo hal bo ha ch s ca tham s Y. B l mt t trng c t vo. Cc gi tr ca Y0, c xc nh t kt qu th nghim s dng phng php iu chnh ng cong, c trnh by trong bng 1.Hnh 9 cho thy m-men xon phanh ti u ca MRBs loi MRF-140-CG vi dng hnh hc ca khi lng phanh l (L/R) khi t l mment xon ln hn 20 (cr=20).ng ch l khe h ng dn MRF ng dn (d v do) ln hn 0.6mm nn d dng sn xut. T cc kt qu,trong s nhng loi MRBs, loi hnh T s to moment khi dng hnh hc 0,6 (L / R> 0.6). C th, khi t s L/D ln hn 1,5, mment xon phanh ca phanh hnh ch T l cao hn so vi cc loi MRBs khc.Ni bt nht l MRB dng a c kt cu nh gn v n gin nht, tuy phanh ch hot ng tt khi L/D c gi tr thp. Kt qu cho thy khi L / R