Giáo trình ma sát học - Chương 5 docx

Trong qua trinh mal moo, caet>t\ m~nap 'ghep'$e trt1C1ltLtongdOlva nhau dan c1~nSlf ~tva begay nhung cheSnhcip nh6, ~o thanh nhung nhcip nhOmOi.. Nhltng':thantttlfU cUa nh~u khoa hQe tiO

CHUaNG 5

f· ,- " A ' ,

hOng t,-ong chi tiit may •

)<hal o~mco bcint~:m6n,~a~p ma aat va chi

chuy6nd¢~tltang d6i cUa cae chi OOLtrQngd~u k~n slr-dyng_,~ythlr ngh~m~Ngoai v~t I~u hinh dang cae

~ m~t tl&p xlie, slrGhu~n d~g tU'sngdOl, alp ma sat

c6n d~c,tr~.g ,bQi mO trltdng xung quanh trong do cO

d~ng va chAt b61tran ,

- K&t cciu ma sat la k&t cciu may cO chli'a cae ~p

ma sat.

, - CllOng d~mai mon Ia ty.~ giil'a d(l mi>ochi ~t (~y mAu thL\').vOiQuang rduanQma sat hay kh6i IU'QJlg c6ng v~e ~,hoa.n thanh

- TOed¢ mon Ia ty 50 glcta(t¢ mon chi ~t va thdi gian xay ra sl! mal mono

- ~ mon glOih~n cua chUi6t (ktit cciu) Iad¢ mon

ma n~u sU,dyngtkip sa hU'hong, khOngkinhtEi, ~ khOngct;lo, phep vi gjc)m~ tin c4Y cUaCd diu Sl! mon

trU'dO.aD suAt va v: b6i tran va vftt I~u

j \Ph~ thul}c ~o : D~ng dl},ng hO,'trtJ¢), ap su~t vav, bO,itrdn va v~t I~u.C chuy~n d~ng (Ian hay Mal mon la slf thay dOl m~t cach tertU k{ch thtJOcchi tkit xay ra khl cO ma sat, va ehia 3 1o~1:mal mon theo dtJong, th~,t{oh,trQngkrqng." !' ,~~ ~C_'

HLthong'fa qua trio~.·fhay.40Vo.,,' , ~ -."- •• •.-:' - i ~t, khOngd~u v~

t~ng thai hinh flQC;cU3 cae b6 m~t tna sat cung nhLt~u true va tfnh ch~hcae lap ~ m~t

Trong qua trinh mal moo, caet>t\ m~nap 'ghep'$e

trt1C1ltLtongdOlva nhau dan c1~nSlf ~tva begay nhung cheSnhcip nh6, ~o thanh nhung nhcip nhOmOi Qua trinhdo 0lt·tJ&pdt!n va sl.! ram nhan cae ~ tn~t ma sat Nhltng':thantttlfU cUa nh~u khoa hQe tiOOnganh eho phepta phAn UGhqua trinh mal mon thanh 3h~n tLt<;1l1g:

- 51.!ttJdIlg tae cU2I cae ~ melt ma sat

- 5lf thay t16ixay ra1torlQ ~b3,'m~t1ttm ~I

- 5lf pha huy cac M m~t ciy

Sa h~n ttJQJlgtr6n khOng ngCtngxcio tr~n va anh hU'c,.,grlWntlau TLtdttgtae cae ~ m~t cO th~ ra Cd hQe h~e phAn tlr TtJdflgtaecdhQc b~u h~n bang Slf,earn

nh~p va mae nOIcae phan tlr nhap nhO;Tltdng tacph~h tlr b~u h~nt>ang slf bam d{nh va xtImthlfc

Chli y rang d~ don va d~ :deo eua v~t ran phlJ thu~e~ngthal eh!u Ilfc vatronglOp' ho~t d~ng cO th~ xayra mQibitin rl61hOaIy gan rr6nvOl qliatrinh ma sat

+ Slfthay dOixay ra trong IClp~ m~t kim loqi: sq thay d~i troFiglcip.~ m~t me sat IiJdo slf bltin d~ng', sl:!

1ing I6n"tUa nh~ d~ vatae d~g hria hqe eaa m6i

tntCmg xung quanh.

• Thay dOi do b~n d~ng xay ra nhll sau: NhO'ngb~n d~ng dan he; nhiOu IAn'do-at! khang hoanth~n ct.ia cciu true trong nhO'ngd~u ~n xae dtnh cO th~ dAn d~n slf We mot cae ~ m~t rem, o:)n Sl.!ibt6n d~ng dah h6f'nhtAu'tAtIt nhO'ngnhAp nh6 vi m6 cUs'~ m~t

B~ d~ng-deo thay,dOt cAu true elIa' ~t I~u lop

~ m~t WltiJ slf t&g h<;lpeua bcSnqua trinh quan trQng nhAt: Slf tnl¢ theocat'm~tpllcing tin'h th~, Slf sOngflnh th~, Slf ~ch cae nguy~nta ra f(hUJVl'1riban cmuitrOrlg m~ng ciJngva chuy~n d¢ng nh~t ct.ia chung, va slf pha huy cciutruc

Bi6n d~ng deo " nhi~t d¢ thap han nh~t d¢ tai k~t tinh dAn dAn b~n Cling va lam Mnldp~ mi[lt Nhltng d¢ Cling vi m6 ngay tr~n ~" m~tcciu"tru~.giarn xuOng, d~t Clfed~i 6 d¢ sc!lunao do rOi g~.rn d~n gici tr;

" ,qogQ ~g cU~,(~pthianhphan~utrue khae nhau'YiJ' '. tj,p;: "'~' d~ng',': '.nh~u 'lcinct.ia tat trqng,I~c dauxciyra" , "

sl/ m~J mqn -fJ1~nhfl~n m6"1 AP,. suAt irAn caq th~nh pha'nClin~ 'Ulng;ep-chungvaQ n6n,m~m Dll~i,tac ,dlJl'\Q

ct.iallfCma ~t m¢t 50b!pt)ei va,va divh.~uy~n~ Do do

, :,,'; k:''.;._ oj -." - ,- ;'.,: • ~.~.r·.' ,r l:'~,,' ," ~

.cOs,!iarn gjitu cae thanh, ph6ncllu,tnie Cling·tr6n ~ mi[lt

• Th~ydOido nh~td~ta.ng: "

N~u nhlttd¢cij_c IdpM ~t cao h~ nh~ d¢ tal kAttinh

kifJ.1~~ 1dP,t?6mijt sa· kh6ngb~ ,pY'Ogma hQa m6m (xayra 'do slf Ia'mphcing nheln~ mc}t, slf chay eua toan

b6 kim~j hay chi m¢t thahh phAn cUa;hc;Jp kim) NhL'

d¢ cao va b~n dqng deo tqo thucln lc;Jicho-cae qua tri khu!ch;tan :

Khi cO sll tang nh~td¢Cl:Ic b¢ va'lam~nh nha

,b6-tlllilt bang kh6ikim ~i 'lAy quanh,cO thA'Vlo:ra a1\1.trUc flhu khhtoi , ; ',i

SI.[,bi6n ~ng;1:ieo,sll tiing nh~t va bkin dtit tn.ie cO th~ xay ra dOng thai hay ri&ng b~t va.gAy ra'

~AtJlOng ~t l~u.Ung suAt nay cOth~ Jam ra dlIu trU

'Khtngh~n cti'u vi mO sll ~p xuc cae chi ti!i tro d~uk~n tat trqng va nh~ d¢ caoda Me t1tnh kha na

tqora,c;cicmacmaplattna ~ , " ,"-"- :·U· ~./ i·i.·, 4

.~-111 '

•••••••• f' ,.

1 cAlItrue ban dAu

3 Plalrml

• Thay d6ido ~e d~ng hoa hQe Clia mOi trLtdng: MOitrLtctl,g khOng khl tqo tr~n ~ m~t'kim Ioqi dltQC Ja

sqGh~hg q~a'ttihh mafttlohalc"mang 0 xyt Mang'

'xYt'bab~ ~ ri1~.tkh6i b!'kAm 'thlj'e v~ la yEiu t6 qlJ

trQr1g khOng nhOllij trong ma sat khOng bOi,trdhh~c

fran 9idi~h~n rrla ba::trdng ma' sat naa~aYdt.Ma·~ga X

gop ptlfJn lam giamCltdng'd~ 'ffi6nM m~tm~;Sat

Khi tae d¢ng vdi cac'chAt ho~t'c1¢hgpha tro

chat hda hQc <i):\lai tr6 tltong t~,~atlg 0 xy{cacm~.

fl,ay ,qaQ::v4 ~ 'h.~" ,q~ ,};l6,~t khqtJ,llPo, n6u, t6c d¢~o

:If:~ ~g ~ xyt ~hixay fa 51.[,phAni;lUy Ph.6tbOi tran " nh~t d~ cao cO kha nang Mn h6a:.b' m~t bang

"-"'i ;GOncacch~~~rw va, kpi.h~t d~9 $i~J;lmtang

+.&1phci ~y·-\ca,eWm4t ma sat:gOm cae(j~ng

• SL!~~ ",t!Tl~:q9nhUng phcin"U):cling cYa h~t mal th~f~P d6n mQtd~ sclu nh:lt d!o~ ~y ra

• T~o v!t Xltac: khi trlt~ phan t<r ~mnMp,'bi,ep sa

ph~.<Jltcili~·thanll" v~tXU'dc V6t Xltdc mat di khi

ma sat cae vcjt Xt10c xuat h~tr'tl ~.ma.t ma sat

• St! bpng 1ach;.Trong sll~y dep,' v"t I~u bi dtiy v~ mQt'phfa ~ b6 m~l.maaat tran ~n Cf;icr.-mang 0xyt va,matmouten h~ vOl klm 1o~1gOen'n d6 b! tach ra , khi kI;t~ -cQ,n~ nangti4P.tl:l~ ch~y N~1,I ling ,suat

I~u sa xuat h~n cae vtit nl1t, dan dtin 51! bong tach v"t I~u dU~ da.ngvay i" •• ,

• kh1rTlCl·$CitSI!trck: Ia ~nftPJlhOngJan~~e PhilOphObitincUa ~ ~tt&:r b!troe fa cO th~chi tkitfa cae thao~pb4f1q\u true cling ~ h9P;~ &au khi mon

,.<~.~.;•••"',-• s .•

h.t n6nfrl~m; cae phAn tu.cua.Jeptrang, cae ~t nho cUa gangxam, ~epMntJ QJa Idp kim ~I chOng

, ma saH<hi bj mongo Nguy~n nh~n;sl! trae Ia do thanh U'ngsuat dli va ung slditnh.,t Vi ~y, slf : ~n cUa' vet mi1do haHo~I!dng''suaf~n iii d~u

• Sl! bili ~u: xay ra trong eh~u ~u elIa mQt t cae~tkhl ma mOIIi&h Ket ~othahh tltang tae p

ta b6n vang hdn mQt h~e ca hai v~t I~u.·· "

ra trong tat ca cae d~ng ma sat tn)' ma saf ltdt; ';tfOtlg"cii cae nguy~n' d6ng cAt, tan va ~p ghep bul6ng: '~" m6n chI xciyra 'khiaie phantlf: chuy!nrakhoivung ma saf" ,',1 '

• ~ mol khi;mal'mOncaeBiYn~t'ldm ~r:sqmal

~t mn khi ma sat gl6ng vdfsl! 'phahuy chung mol, chI 'khaenhau (, ChOla qua trfnh mon cO quan sat d! dang, cOnqua tn'nh mol gan nhlt bao

, ' ,~, ,; 01- : ': -: ,

cUng b~u h~n' bang slf ce bAtngo

• Anh huang eua ma sat dao chltu c16n;Sl!mal m

st!'thay c16iphudI'lg chuy!n c1QngseJam gtam c1~ mOrl trong ma sat tru¢ eung nhu ma sat tan

tMrit'cae chat h~tc1Qng ~ mc}t vao dau hol t! Il/ema;~t va caebltirh:t~~ ~~~'f(c18rt-h6~ g' c1i.Sl!khae nhau giita ma sat 1 chlAu ~a(lao eung giam

• cae giai c1o~nmid mon eua ~p ma sat :

.' NAu coitMJehoanh Ia UfClfglan'tam~ct'cjja

ma sat, uta (fQ man iii thJCtung, ta cOdl.lOng cong mai mon chi t~ftheo thbi gti:!n Tang eoagac ngh~n giO'atiep tuy'nducing cong ~I mQtc1~mMt kY vCIIt

hoilrih'sa xae (f!rih tOe(fQm6ll'~i'thOi (fl!m nay

Dl10ng cong mai m6n

bJ<hl!'.lO f9 ~i.~tdn d.in~ '

d Ung.ydr~~~hi ti& chiu ~ng suM t~ xaic, {h~ tl; '1<h6ng bi mDn

trong·giai~n'1 , , ,.,;

;n ,&, ttull'tnOn 6n 'djnh: khl sLt d~ng binh thUdng (do~n'tiling: cUB dUCShg oong)

lit QUa' trlnh: tAng' vqt- cUa t6c ~ mon, tUong ttng vdi giai 'do~n mookhOc 1~1.

Sau khi ~p rap, chi ~t tlAp xUc nhau theo cac phannHO1&net'Ja d~ nhap nhO bA,m~t Trong glal d~n

dAu,d~1i UGh· ~p xuc thl/C fA nhO; khj, tang.tai~ cQsp

suAtldrl'viJ b~n~d~ngd80ldo.M~phim d~ nhAp nM~ m~tb!nenep,m~t phAn'b! pha huy 6 phAn nhO ~n va

kY Do do dlldng oong mai monphai la ~p hex>I~n tl:lC ,~c 4~~ ,ooogv~V,\J.ng~¢kh0rl9 ~~m

D~ 9M ' 00._ ng~mc\i'mon bi!."~,tt.! qu y I~~t mon theo thai glan~'j:Shi~n"thiAt, cO th~ dlmg dltQng cong mon the<?}~'~aFlgduong ma sat hay theQ.m¢t thOng sO.d~c

~ Ttll!ct6eo th" c9:1. ~ytiuJ6 khac anh 'hUbrJg, d'n.do m?>ncl}i1~lXetv~~~fa~nh,90 khffa quan tAlJl <!tinslf rung do.~9;.Kbi nghiltn cuu slf'mai mon cac chi tkit cUa tNc truy6F'!d¢ng may ~~'" ngltOi taxac d!nhbang thlfC 'ngh~~t J;.r~l/rung d¢ng ~~ ~,i.lt9rg! du' khOn9,,Idr'lh(jO

10 - 2~ t:Ji trQng sa dl:ing trung binh, ciinglam tang

, J' r' : , ••

,t<h.i~on6n cac b~n d~ng thay dOi cua ~t I~u a

vung~pxuc 9ci~~;mclt I3p ghe~,t:J,i, ~9ng, do.ng,da

lam )(u~th,itv.;dol1Q ~~ncam,U'ng,thaYd6i troFl9 Idp:b~n;;,"~ , •• -' .•••••.• _'" J,. .' ',' l .:' ''',' , .i r

, dang Sl! ttla,y.'deli cua tCtthOn9,f90ra SUc d~n ,d~ng cam'li'ng trong, khuog (hinh thaijh 40 cae 'chL$fl3p

hll'dDgr<4~nd~n tra va th6 _h~n Jrqng, v~n.g ti6p xuc Ia

._.~,~, ',,,t ••. ,~~.:- '.' ' ":' ,i •••. 'J'"i:, : - ,'~-~"',

n~uX~nbn~~",~~; slf h,()~thOa,;P6 m~t,,va SLfphat, ~n mal rngn °.x.y hoa Slf ~m JhLfc'-vaeac qua trinhan ,m69,j1~.~ :hpa)amg~m_' {~6(t~9 cU~ m6i.,~p g~ep-':nit nh~u H~n tll<;'l1gnay gp,i fa h~n tll909 _(f~.n.,d¢ngllfc cUa~sVrt!~~m~n ;~L!a(ic1 ~as~ ~~re~:'~h,ungb¢ ~f} ghep khac nhau {b¢ truy6n ~~, (tang,' mOi ghep .) d~ ngh~n Cli'uthLfc nghi6m h.~n tU<;'I1gnay Chung ttll99._~~.tai tr6ngia thr ngh.~&'vdldclctin~' bi6n d¢, ~n , sO c4'i1~i trRng dQng Lin.gv~ gfc:itr!,thlfc, t6 khi sa dl:lng

tre gia~ cac b6 m~'t ti6p xuc, nh~t d¢, danh gici o~ng xu~f h~J1d~n Uch dua tac' dl}ng cUa tai trQ 'd¢ng wtha ngh~m so sanh ~ m6fl.Ter ~~~qua IJg~~m dlfngduQC cac dUdng,cong cUCl.sLi'cd.kln d¢

; f, _ "._ • ' _ ".,' r, , , c.a1,1lU'ng,plJl:I thu¢c bi6n d¢ va tAn sOcu~ iai trq d¢ng N~uR~n~9khong d6i,sLi'c d~n d¢nq camY~.~

~ vQ( tan ~ taitrQng d¢ng Do d6.• ter thOng ~m

th~y'.d6tnhi6u nhtJtQ.1' t}~• SI ' :' _ :L.' XYI19- -!, _ tAn sO cao cua ta~trQng.'N,- i'.-i"

<

.~n~·,~~nfJ,,~6i, sU:c.~~.n d¢n9,.can,'l,U'ng,cilnQ,.,ta

-cong d¢ cUng vO'ngtheo,ap sutJt ' !~'" >;.! ' '

Slf tan~.b~n d¢ #i ,V~~g.<1¢f,l,~,,- i ' - , _' - '- - ,., " ~, "vt; ·' , IarTl-:'xy~t' ;, h~n, gu~ trin~t~1 riguc;Jcnhau Slf tang cua ter thongca

•.;~ dart:~~n' s~ tang cua h~u d~n th! va S.lfgiamq~

d14ntrb lam hl6u d~n thti g;am theq Theo quan d~ d~,n '~¢ng Ilfc, 1a(frQ~.9'd¢ng oo'mn'SO cao va bk\n

:'- L' -" ,- ,'::'-.' ',' ~ _.,:, '_.,, _,

~!1o.~.cQ I~'rih~t n~ncan Ull[c h~n'nhltng ~u y ~u nAngcao tu6i thQcUa chi OOtmay: nhu ,giam.taittQ' d¢ng e ph~n ~r{s6 cao va ~o ra lhlg su~t ti$p'X:~c d!nht]qQ!U'ng suAtd~.,,~~nq9Idp b~ m~t bitin d~ng,_la'

dAu ap suAt va giam d~n irb 'tkip xUc trOn ~ se.dl

;chuy~n ch9"~'tQcktli rna siit, sJdl:lng; ch~(bOi trdi;l• ",t '.',-,,', '; •.• 11I' , •• d

d~nJ slt~t.!ng cac cl)tJtbao v~

• p~~n.~,i d~ng, mon Anh h.uRng:;ef~di~~"~n' sat d~n dqn~ ":l0n:,

; -e~~n ~i dCJng.mo~:

d~ncac Idp kim ~1b6-m~tbi r;;~t ,~ t~t trong 'khi' m~ sat,hoqt tlnh b! bk\n dqng deo va?O tJdng ta~gl

I· •.••• !

Ii 1/'\

61

xy'Ctia khOng -Idlr h~ cUa dau bOHrdn6l'hap 'thl:' tr~n M

cac Idp mang hap thl:' h6a hQC,mahgcUa cae du:rig dich '~n;' enatac hQP'chathda' hQc glOa' kim' ~i va 0 xy va

'il!'Dong' tach cac fap tTlangay ra khol ~. 'm~t·~sat.

S\!ih'~(1'moh,:~ijJHo~Haqua- trinh 6n dtnhttflttW(d.~·sl}'

~n'ba~g' ~rigg~ pha ~t'vah61 ph~cciicTdp mcihg O' xyt 'vii !'(J~(;tnmg"chd'dliti ~n sa dl:'ng' 6inh thtthng

+ Mal m6n va hl! hong do mai m6n:ta qua trinh pna 'ho.fl>6 m~t chi t~rkt1icO"m6Itru~g mal trong

.,;ill M8fftndhcd hOaxay ra khi:

":I!er :;c- HkIt-f m'>0, 6

.•.• ·:dOceli'ng klm loa I

, Hm:'(fQ k 'r:;,rong~lmai. '

Malmon Cd hQc'xay ra khl KT <0,6,

."~l'Ig, '.nay thuQc v!'nhang qua trinh hl! hong kh~rig 'ChopHepxay ra khl cOrTla sat .' ' , , • iTtdc 1a qua trinh hl! hong khOng cho phep cUa cac ~ m~t ma sat do ktit qua cUa sl.! hinh thanh cua m6i.nk6t klm 1o~lc~c b¢,sil6f6n d~ng va sq phci huy cae Mrfk6t ay, kern theo ~e bong' ~eh cae h~t klm Io~i :haybam'ictfnn,cac h~t ay~n ~ m~ttkip~xuc,

·:TrOc xuAth~n khi rtta'sattrl!¢, van6c d¢ d!ch chuy.ri'tfrdng'd6tnhova cip su~h vitc;rtqua glOi h~n chciy

,~~Ongtd~nghU hong~y,cO th~ix4Alhit~-flgay ca tro

- Troc nhit)t:slJ, • ' :. xl,I4i:,': , '",:hi6n cacliAn~t•. ' • t ••>_- ~,~;kim. ,Y-9n~,qua1,rinhtroc n~* -'.- r . r ado sl!n~ng, n~d.m,m''" r,

;bk);o d~~9;vfI bl6n q~rw:~a ca9,~rpc}t tl:1u4n~~t~ ~ ,n~n Tr:O~,gh~t,p'!?~,}hy~cvap cac !in~,$itn~ittlY ~' velt1~4-: d;1fuQHh ~ !foh On d!nh nh~t, dO-cUn,gioQ nh~t dung,tinh dan nh~t va ,iii mQt h~n ,WQr:\g qg, :hi6l1\~aJ>hp biti~h,' '.,:: , ",:., '

,.:V)~ t;Hll",,b,ongd,o mol: xuat~~r)o rmW1gchj~t,t'1l:

trqng thai Li'ngsu4t Delc tinh roll y6u va slf p~

cUa cae hu hong mOi,4Uc;ICxac dinh b~)~R)~ei trin blAn d~ng deo Iclpdi ~p ~i bdi $I.! Jam,~,~ vii pm b6' cae lOpkim Io~iM melt, bOi,:IWP~a~,~nh'~c.f.\'ng su

du va b6i h~n tUCJI1gmoi d.gl~~;~"ph_[h~i ~ m khl b! hu hong moi dUc;ICdelc trung bCJisl)' xuAt h~n cci

vet nltl tA vi, cac mnh trUng ph4n nhom hay d~c ~p

.-: Qua trinh fretting: xy~t h~n khicO masat tro,

v~ nhOng'Chu~n ~g :ij,llh ~f1.~qtl~t"h4.~ :ktK"

~c d¢ng cUa tal trQng d¢ng,~G tnrng cho fretting iii s ch~y6nv! nh9 cUc:1bi'mc}t Japghep,

- Sl)' ~,p Iun: la,'.b,i4,''nd~,ng,"deo th6 t1chvi ~ .gJ, •

,kim~i, di IkiDvaJ sl)'th~Y d6i'nir\h ~ling ·v~~c

trqng ldo hon giqi:h'ln chay akin d~ng va ep IU,ncO th Ian tran.1qan ~:hay m¢t ph~n ldo ,~ tichJrUa chi ti6 m~y Khi'~ep lun"••<'.:• th~tioh chl'~'-.1 -,' thayd~1AAUR'.', '-.:' ,-,,' kh

vJaao:m6tt kift~i:g6m.bao mon Cd hQc do nh(}ngdong·itiad1Atf6"g hay kWi~p di Ic)p kJi Ngoal I'a

cOn bao mon d~n do tac.d':lng d~n nh~t >cUli $t;f phong d~n kh6ng cO djnh d~ng xung gc1yn~n.

- Slf an mon: pha h~i b~ mc1ltdU'a tae d¢ng hoa hQc hay d~n hOa hQc cUa m6i trlloog.

- Slf xoi mon: Ia qua trlnh pha h~i ~ mc1ltchi ti6t

~p xLie va chAt lOng C?huy6J1 d¢ng va v~n tOe bi6n th~n St;fxoi mon gc1yra cO tfnh- chAt ~c b¢ va th~ h~n

a~e hinh thanh nhO'ng v6t 16m va cac 16h6ng.

Sau dc1yla so dO phc1n Io~i cae d~ng mon va hU' hong:

Qic d~ng pha ho~i ~ mc;.tchi tl6t

clio Ilh'P heo m6n KhOng clio ph8p(HtlhOng)

~

'" 3 tt

•

~".

, .•.

~II'~

~ ,~ ti ~ Ii

~

-4: ~ ~ ~(

'.~J I~)c :.c ~ ~~ ~ ~

'g ~j' (;"t ~ Ie E

~ " ~ w

~ "e:

~

Olan,rang banh rang &\u cO thA xay ra cae

':1'