chuong 2 bien dang deo .pdf

7/25/2019 Chuong 2 Bien Dang Deo .pdf

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Chng 2: BIN DNG DO V C TNH

2.1. Bin dng do v ph hu


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Th ko mu thp (Movie)


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2.1. Bin dng do v ph hu

dn di l

Titrng

F

Fh

a1

e

Faa

b

c

Fb

a20Biu ti trng - bin dng


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K/n: Bin dng do l bin dng d khng b mt i sau khib ti trng tc dng.

ng sut tip gy ra bin dng do (trt), ng sut phpkhng gy ra bin dng do.

a) Ban u: cc nguyn t dao ng xung quanh v tr cn bng.

b) Bin dng n hi: cc nguyn t x dch phm vi hp so vi thngs mng, c th tr v v tr ban u khi b ti trng.

c) Bin dng do: cc nguyn t x dch phm vi ln hn mt thng smng (trt), khng tr v v tr ban u khi b ti trng.

d) Ph hu: lin kt gia cc nguyn t b ct ri

2.1.1. Khi nim v bin dng do


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2.1.2. Trt n tinh th

Phn

gtrt

M

ttrt

Trt trong ntinh th Zn

Hin tng trt trong n tinh th

/n: Trt l hin tng chuyn di tng i gia cc phn tinh ththeo cc phng v mt nht nh gi lphng trt v mt trt


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Mt trt: mt (tng tng) phn cch gia hai mt nguyn t

dy c nht m ti xy ra hin tng trt

Phng trt: phng cmt nguyn t ln nht

H trt: L s kt hp gia mtphng trt v mt mt trt

a) Cc mt v phng trt

- lin kt gia cc nt bn vng nht

- khong cch gia 2 mt l ln nht

Mt dy c nht?


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H trt trong mng A2

H mt trt {110} : 6 mt trt

H phng trt : 2 phng trt

S h trt = s mt x s phng = 12 h trt


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H trt trong mng A1

H mt trt:S lng: 4 mt trt

{111}

H phng trt : 3 phng trt



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H trt trong mng A3

Mt xp cht nht: (0001) S lng: 1 mt trt

H phng xp cht nht : 3 phng trt



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Kiu mng

S mt trt 6 4 1

S phng trt 2 3 3

S h trt 12 12 3

Kim loi Fe, Cr, W, V Fe, Al, Cu, Au Ti, Zn, Mg,Be


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Din tch mt trt: S=S0/cos

ng sut tip trn phng trt:

t= (F/S)cos=(F/S0)coscos

= s0coscos

b) ng sut gy ra trt

Phng trt

s

0

s

Mt trt

S0

ng sut tc dng

nh lut Schmid

F

F

+ 900


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t= s0

cos.cos th

nh lut Schmid

tR= 0=90

s

tR=s/2=45=45

s

tR= 0

=90

sa) b) c)

Khng xyra trt

Khng xyra trt

D xy ratrt

= 450

= 450 = 900

= 900

b) ng sut gy ra trt


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c) Tnh d trt

L thuyt: tth~ G/2

Thc t: tth~ G/(8.1038.104)


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c) Tnh d trt

Chuyn ng lch trong n tinh th

Lch trong n tinh th LiF (x750) Chuyn ng lch (Movie)


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2.1.3.Trt trong a tinh th

a) c im

Cc ht b bin dng khng

u

C tnh ng hng

C bn cao hn

Ht cng nh th bn v

do cng cao

sc=s0+kd-1/2


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b)T chc v tnh cht sau bin dng do

Cc ht c xu hng di ra theo phng bin dng

= 40-50% cc hts b phn nh v ko

di to th = 70-90% cc htb quay, cc phngmng cng ch s

song song

t chctextua bin dng

T chc

Bin dng ht tinh th (Movie)


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ng sut d ln

do x lch mngtinh th (tng mt lch)


Tnh cht

Ht tinh th b kodi theo phng bindng : tnh d hng


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C tnh thay i: cng, bn tng, do v dai gim.


Tnh cht

in tr tng, kh nng chng n mn gim

ch,MPa , %b ,MPa

Mc bin dng , %


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2.1.4. Ph huKhi ng sut > [b] ph hy do t, gy, v

L dng h hng trm trng nht, khng th khc phc

c thit hi v kinh t, con ngi..cn phi c binphp khc phc

c im chung: hnh thnh cc vt nt t vipht trin vtnt tch riph hu


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a) Ph hu trong iu kin ti trng tnh

Ph hu do: km theobin dng do ng k.

Ph hu gin: khng km theo bin dng,gm nhiu mnh v.

Ph hy do Ph hu gin


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a) Ph hu trong iu kin ti trng tnh (tip theo):

Ph hu dopht trin vi tc chm, cn nhiu nng lng

cng ph hy lnPh hu ginpht trin vi tc rt nhanh (1000 m/s) , cnnng lng nh cng ph hy nh hn

Ch : vt ph hy c th ct ngang cc ht hay theo bin

gii gia cc ht.


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a) Ph hu trong iu kin ti trng tnh (tip theo):

Ph hy do hay gin l do:

+ Bn cht VL : thp, Al,Cu - ph hy do; gang,ceramic ph hy gin;

+ Kt cu gy tptrung ng sut VLdo b ph hu gin

+ Nhit thp, tc t ti nhanh VL dob ph hu gin


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C ch ph hu do

SiVtct

1 2 3 4 5

1. Hnh thnh c tht (bin dng do cc b)

2. Xut hin vt nt t vi

3. Cc vt nt t vi tch t, pht trin n kch thc ti hn4. Vt nt trn ti hn pht trin nhanh

5. Ph hu vt liu : vt ct (450) gn b mt ni ng suttrt ln nht , t chc si bn trong li do bin dng do


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Vt nt t vi Mm ph hy VL

- Vt nt khi kt tinh, ngui nhanh;

- Cc r kh, bt kh trong vt c- T cc pha bn thp trong vtliu (graphit trong gang)

- Sinh ra trong qu trnh bin dng do c tp hp nhiu lch

cng du chuyn ng trn cng mt mt trt v gp vt cn(pha th hai)

Ct gang xm(Movie)


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b) Ph hu trong iu kin ti trng chu k

c im: vt liu chu ti trng khng ln (


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Mt gy khi ph hy mi

b) Ph hu trong iu kin ti trng chu k

1

2

3

1- vng nt u tin st b mt(mm)

2 - vng nt pht trin chm, nhn phng, c di phn cch

3 - vng gy tc thi c tit din nh nn ng sut ln.


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2.2 Cc c trng c tnh

C tnh : cc c trng c hc cho bit kh nng chu tica vt liu trong cc iu kin tng ng,

+ c s ca cc tnh ton sc bn, kh nng sdng vo mt mc ch nht .

+ c xc nh trn cc mu chun nh.

- Mu th ln thng c c tnhthp hn.

- Cc ch tiu c tnh thng dng :

bn, do, cng, daiva p, dai ph hy.


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a) bn tnh (s)Tp hp cc ch tiu v sc chu ng ti trng tnh ca vt liu


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a) bn tnh (s)

Gii hn n hi (sh):

l ng sut ln nht, sau khi b ti, khng lm mu b thay ihnh dng, kch thc.

)(0

2,0

2,0 MPaS

Fs

Fh: lc ko ln nht khng gy bindng mu sau khi b ti (N)

So: tit din mu th (mm2

)

Gii hn chy vt l (sch): l ng sut b nht gy bin dng do

Gii hn chy quy c (s0,2):

)(

0

MPaS

Fdh

dhs

F0,2: lc ko to ra bin dng d 0,2% (N)

So: tit din mu th (mm2)

)(MPaS

Fs

Gii hn n hi quy c (s0,01, s0,05): )(0

01,0

01,0 MPaS

Fs


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Giihnbn

mt lch

1

2

3

4

Gii hn bn (sb):

Fb: lc ko ln nht trn gin thko (N)

So: tit din mu th (mm2)

)(0

MPaS

Fb

bs

l ng sut ln nht tc dng ln mu gy ra bin dng ccb (hnh thnh c tht) dn n ph hy

Yu t nh hng n bn: mt lch

1. bn theo l thuyt

2. bn ca n tinh th

3. Cc kim loi nguyncht sau

4. Kim loi sau bin dng,ho bn

108cm-2

1010-1012 cm-2

Si Fe: 1300 Mpa

Fe sch kt: 250 Mpa


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Cc bin php ho bn vt liu

Bin dng do: tng mt lch bin cng, tng bn;

Hp kim ho: tng x lch mng, mt lch tng bn;

To ra cc pha cng phn tn: to cc chng ngi cntr chuyn ng ca lch tng bn, cng;

Nhit luyn ti+ram: to qu bo ho tng bn, cng;

Ha nhit luyn (thm N, C): tng bn, cng bmt, chu mi mn, chu mi;

Lm nh ht: tng tt c cc ch tiu bn, do, dai.


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b) do (%, %)

Mu trc th ko Mu trc th koMu sau th ko Mu sau th ko

K/n : L tp hp cc ch tiu c tnh phn nh bin

dng d ca VL b ph hu di ti trng tnh

Cc ch tiu: gin di tng i & co tht tng i

%100.%0

01

l

ll %100.%

0

10

S

SS

l0 l1


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Tnh siu doNu

% t t 100-1000% Vt liu c gi l siu do

u im: - Tit kim c nng lng;

- D ch to cc sn phm rng,di, tit din khng u, phc tp...

Bin php t hiu ng siu do:

- Lm cho ht nh mn, ng trc, ng uv n nh

- Bin dng nhit cao (0,6-0,8)Ts- Tc bin dng rt nh c 10-3-10-4s-1

Thp siu do lm v xe

Hp kimTi siun hi

) d i ( )


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c) dai va p (ak)

Khi nim: Kh nng chng ph hy ca vt liu di tcdng ca ti trng ng

) d i ( )


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(Charpy)

initial heightinal height

sample

c) dai va p (ak)

Cng ph hy tnh cho mt n v din tch ct ngang mu

S

Aa

k

k Nm/cm2, kJ/m2 v kGm/cm2


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Phm vi p dng:

Chi tit chu va p: ak>200 kJ/m2

Chi tit chu va p cao: ak>1000 kJ/m2

ak sch (s0,2) x

Mi tng quan gia ak v (s0,2x)

Cc bin php nng cao ak

- To cu trc ht nh mn: tng bn, do tng dai;

- Ha bn b mt tng bn, cng, khng lm gim do tng dai;

- Hnh dng ht trn, a cnh c dai cao hn ht c dngtm, kim.

0,8-1% C

0,2% C

d) cng


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d) cng

Khi nim: kh nng vt liu chng li bin dng do cc bdi tc dng ca ti trng thng qua mi m.

c im:

- Ch biu th cho tnh cht bmt (vt liu khng ng nht);

- Kh nng chng mi mn cavt liu;

- Khi vt liu ng nht ( phi): biu th bn v kh nng

gia cng ct ca vt liu;- S dng mu nh, n gin, nhanh chng, khng ph hy,c th o trc tip trn chi tit ph hp vi iu kin snsn xut.


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Nguyn l xc nh cng:

p ti trng xc nh ln mu thng qua mi m bng vtliu cng to vt lm trn b mt; vt lm cng rng (su) cng cng thp.

Phn loi:- cng t vi (dng ti trngnh, mi m b): xc nh cng ca cc ht, pha trong tchc ca vt liu;

- cng th i (ti trng vmi m ln): phn nh kh

nng chng bin dng do canhiu ht, pha --> xc nh cng chung cho VL;

- K hiu bt u : H (hardness)


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cng Brinell (HB)

Thp v gang: D=10mm, F=3000kG, t=15s

sb = a.HB (a = 0,3 0,5)

u im: quan h bc nht vi sb

Mi m: Bi thp ti cng, ng knh D

Nhc im:

- Ch o c cho cc VL mm,mu phi phng, to, dy, vt lm to;

- Khng cho php o trn cc loitrc, thi gian o lu.

cng Rockwell HR (HRA HRB HRC)


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cng Rockwell HR (HRA, HRB, HRC)f

f fF

h (mm)f: ti trng s b 10kg

F: ti trng chnh (90kg cho thang B, 140kg chothang o C v 50kg cho thang o A)

HR = k - (h/0,002)

k = 100, thang o A, C, mi m: nn kim cng, gc nh 1200

k = 130, thang o B dng cho mi m = bi thp, D = 1,588

Ch : HR l loi cng quy c, khng c th nguyn

Phm vi p dng:


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Phm vi p dng:

- HRC o thp sau khi ti, ti + ram, thm cacbon;

- HRA o lp thm mng: thm nit, cacbon-nit;- HRB o vt liu mm hn: thp , thng ha, gang c.

u im:

- o c cc vt liu ttng i mm n cng;

- Vt lm kh nh, c th occ vt mng, lp ha bnv ngay trn thnh phm vtrn mt trc;

-o nhanh, tin li ph hpvi iu kin sn xut.

cng Vickers HV


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cng Vickers HV

Mi m kim cng, hnh thp 4 mt uvi gc gia hai mt i din 1360;

Ti trng tc dng nh (1-100kg), iu kinchun 30kg vi t = 10-15s.

Nhc im: thit b t tin, khng tin libng phng php o Rockwell.

u im:

- Kt qu o khng ph thuc ti trng;

- Xc nh c cng cho mi loi vt

liu, mu mng;- cng chun trong NCKH.


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Chuyn i gia cc thang o cng

cng HV HB HRC HRA HRB

Thp 240 240 20 60,5 100

Ti cao 513 475 50 75,9 -

Cao 697 - 60 81,2 -

Cc mc cng ca thp

- Mm: HB< 150

- Trung bnh: HB ~ 300-400- Cao HRC ~ 60-65

- Thp: HB ~ 200

- Tng i cao: HRC ~ 50-58- Rt cao HRC > 65

2 3 Nung kim loi qua bin dng do


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2.3. Nung kim loi qua bin dng do

2.3.1.Trng thi kim loi sau bin dng do

Mc x lch trong mng tinh thln, mt lch cao, kim loi bho bn, bin cng (trng thikhng cn bng) c xu hngchuyn v trng thi nng lngthp hn - trng thi trc bindng do.

Ti sao cn phi nung kim loi qua bin dng do?

- c th tip tc bin dng do (ko si);- c th gia cng ct c d dng;

- Kh b ng sut bn trong trnh ph hy gin.

2 3 2 Cc giai on chuyn bin khi nung nng


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2.3.2.Cc giai on chuyn bin khi nung nng

a) hi phc: nung nhit thp (0,1 0,2 Tnc)

- Gim sai lch mng;- Gim mt lch;

- Gim ng sut, in tr;

- T chc t vi cha bin i c tnh hu nh chathay i.

Hi phc Kt li St nhp ht

/s trong

do

bn

cng

Tktl Nhit

b) kt tinh li: nung nhit xc nh TTktl


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b) kt tinh li: nung nhit xc nh TTktlQu trnh hnh thnh cc ht mi theo c ch to mm v phttrin mm nh kt tinh.

- Xut hin cc mm mi khng cha sai lch do bin dng, thngti cc vng b x lch mnh nht (mt trt, bin ht);- Bin dng do mnh, s lng tm mm nhiu, ht nh mn.

Sau kt tinh li kim loi c t chc ht a cnh, ng trc


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, g

Kch thc ht ph thuc: %, T , .

do tng, bn, cng gim (thi bn)

Tktl = a.Tnc (0K), a= 0,2-0,3; 0,4; 0,5-0,8

Fe - 450oC, Cu - 270 oC, Al - 100oC,

Pb, Zn, Sn < 25 oC.

c) St nhp ht: nung nhit caoTTktl2


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c) St nhp ht: nung nhit caoT Tktl2Nhit cao, thi gian gi nhit di qu trnh st nhp cacc ht theo c ch ht ln " nut " ht b;

S pht trin ht l qu trnh t nhin v lm gim tng bingii ht do lm gim tng nng lng d tr;

Kt tinh li ln 2 lm xu c tnh nn phi trnh.

8s, 580 0C 15min, 580 0C 10min, 700 0C


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Kt tinh li ln 2 (movie)

2.3.3. Bin dng nng


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Bin dng do nhit cao hn nhit kt tinh li

(W Tktl = 1200 0C Sn, Zn, Pb - Tktl < 250C)

T ~ (0,7-0,75)TncCc qu trnh xy ra:

- bin dng do lm x lchmng ha bn, bin cng;

- kt tinh li lm mt x lch

mng thi bn, gim cng.

2.3.3. Bin dng nng


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u im:- Kim loi xt cht, do cao hn, t b nt, khng b bin cng;

- Nng sut cao,dng lc p nh, gia cng c phi ln;- Ci thin ht (pha gin), m bo c tnh tng hp.

g g

Nhc im:- Kh khng ch nhit ng u trn phimng, ln;- Kh khng ch chnhxc hnh dng, kchthc chi tit;

- Cht lng b mtkhng cao: vy oxyt,thot cacbon.

Rn (movie)


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chuong 2 bien dang deo .pdf

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