chapter 1 sbvl
DESCRIPTION
TLTRANSCRIPT
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Chng 1: Cc Khi Nim C Bn
1 i Tng v Nhim V Ca Mn Hc
2 Phn Loi Chi Tit Trong Sc Bn Vt Liu
3 Ngoi Lc Ni Lc
4 ng Sut
5 Lin H Gia ng Sut v Cc Thnh Phn Ni Lc
6 Bin Dng
7 Cc Gi Thit C Bn V Vt Liu
8 Nguyn L Cng Tc Dng Ca Lc
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1 i Tng v Nhim V Ca Mn Hc
* i tng: Vt tht
* Vt lm bng vt liu g?* Vt c hnh dng, kch thc cth
* Vt b thay i hnh dng, kchthc, b ph hy khi chu tcdng ca lc
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1 i Tng v Nhim V Ca Mn Hc
* Nhim v ca mn hc: a ra cc phng php xc nh kchthc cn thit v vt liu ph hp cho cc b phn cng trnh hay chi titmy vi yu cu chi ph vt liu t nht m vn m bo:
+ iu kin bn:
Cc chi tit my hay cc b phn cng trnhlm vic bn vng v lu di m khng bgy, v.
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1 i Tng v Nhim V Ca Mn Hc
+ iu kin cngNhng thay i v hnh dng v kch thc ca chi tit my hay ccb phn ca cng trnh khng c vt qu gi tr cho php.
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1 i Tng v Nhim V Ca Mn Hc
+ iu kin n nh
Cc b phn ca tng kt cu cng trnh phi bo ton hnh dnghnh hc ca kt cu khi chu lc, nhm loi tr cc hin tngdn n mt n nh nh cong vnh hoc mo m.
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* Chi tit dng thanh
2 Phn Loi Chi Tit Trong Sc Bn Vt Liu
+ Thanh c c trng bi trc thanh v mt ct ngang
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2 Phn Loi Chi Tit Trong Sc Bn Vt Liu
+ Phn loi thanh
- Thanh thng
- Thanh cong
- Thanh phng
- Thanh khng gian
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* Chi tit dng tm, v
2 Phn Loi Chi Tit Trong Sc Bn Vt Liu
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* Chi tit dng khi
2 Phn Loi Chi Tit Trong Sc Bn Vt Liu
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3 Ngoi Lc Ni Lc
3.1 Ngoi Lc:
* Ngoi lc l tt c cc yu t t bn ngoi tc ng ln i tngkho st.* Phn loi ngoi lc
- Lc tp trung
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3 Ngoi Lc Ni Lc
- Lc phn b+ Lc phn b ng: , th nguyn: [lc]/[chiu di]q
qT
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3 Ngoi Lc Ni Lc
+ Lc phn b mt: , th nguyn: [lc]/[chiu di]2p
+ Lc phn b khi: , th nguyn: [lc]/[chiu di]3
Lc phn b khi : lc trng trng, lc qun tnh, lc in t,
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3 Ngoi Lc Ni Lc
3.2 Ni Lc:* Ni lc l lng thay i lc lin kt gia ccphn t trong mt chi tit do s thay i hnh dng,kch thc ca chi tit di tc dng ca ngoi lc.
* Cch xc nh ni lc: s dng phng phpmt ct
1P
2P
3P
4P
nP
CI
II
1P
2P
3P
4P
nP
C
1P2P
3P
A4P
nP B
Noi lc
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3 Ngoi Lc Ni Lc
* Ni lc l lc pht sinh trn mt ct.
1P2P
3P
A4P
nP B
Noi lc
* Ni lc ph thuc vo v tr ca mt ct, tng im trn mt ct vngoi lc tc dng ln vt.
* Ni lc cn bng vi ngoi lc tc dng ln vt.
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1P
2P
nP
y
x
zzN
yQ
xQ
xMzM
yM
A
C
3 Ngoi Lc Ni Lc
* Thu gn h ni lc phn b v tm mt ct ta c
1P
2P
3P
C A
4P
nP
B
C
R
R
M
M
: Vct chnh ni lcM
: Mmen chnh ni lc
R
* Cc thnh phn ni lc+ Lc dc zN Ko-nn
+ Lc ct yx QQ , Ct
+ Mmen xon zM Xon
+ Mmen un yx MM , Un
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* ng sut trung bnh:
4 ng Sut
Fqu tb
=> ng sut bng cng ca ni lc trn mt n v din tch
1P
2P
3P
Vi phn ni lcq
F Vi phn din tchA
* ng sut ti mt im:dF
qdFqU
FA
lim0
* Th nguyn ca ng sut: [lc]/[chiu di]2
ng sut c n v: N/m2; kN/cm2
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* Phn loi ng sut:
4 ng Sut
+ : ng sut php n
t
+ : ng sut tip
* ngha ca ng sut: ng sut ti mt im li lng c trng cho kh nng chu ng cavt liu ti im v l tiu ch kim tra bn.
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* Phn loi bin dng:- Bin dng di: l lng thay i chiu di
* Bin dng: l sthay i hnh dng,kch thc ca chitit khi chu tc dngca ngoi lc.
6 Bin Dng
1P
2P
3P
4P
nPO
A
B O
A
B
'O
'A
'B
+ Bin dng di tuyt i: OAAOL ''
+ Bin dng di tng i: %''
OAOAAO
LL
- Bin dng gc (Bin dng trt): l lng thay i ca gc vung' ' '
2A O B
* Chuyn v: l s thay i v tr ca mt im thuc vt trc v sau khivt b bin dng.
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* Vt liu ng hng: Ti mi im trong vt tnh cht c, l nh nhautheo mi phng.
* Vt liu lin tc: khng tn ti cc khuyt tt bn trong chi tit.
7 Cc Gi Thit C Bn V Vt Liu
* Vt liu ng nht: Vt liu c cng tnh cht (c hc, l hc) miim bn trong chi tit.
* Vt liu n hi l tng: khng tn ti bin dng d bn trong chitit.* Bin dng v chuyn v ca vt l rt nh so vi kch thc ca vt:cho php ta p dng nguyn l cng tc dng.
8 Nguyn L Cng Tc Dng Ca Lc
ng sut v bin dng do mt h lc gy ra s bng tng ng sutv bin dng do tng lc tc dng ring r gy ra.