smitov dijagram
TRANSCRIPT
8/10/2019 Smitov Dijagram
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Proračun u dinamičkim uslovima
(odredjivanje kritičnih napona)
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Kritični naponi mašinskih delova u uslovimdinamičkog opterećenja (sa konstantnim amplitudama)
R = -1σ
t
+
R = 1σ
t
R = 0σ
t
σ σ σ
σ g
σ d
σ g
σ d
=
1
;
g
d
dg
R
02
0
0;2
g
d
dg
R
-σ
1
;
g
d
dg
R
2σ
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Wöhler -ov dijagram – nastanak
[σ ]
t
σ SR
σ A3
σ A2
σ A
N
σ
σ SR = const.
σ A1
σ 1
N 1
σ 2
N 2
σ 3
N 3
σ SR σ D
σ A
σ D
N D
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σ A
Wöhler -ov dijagram σ = σ ( N )
N
σ
σ
SR σ
D
const.m N N
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Wöhler -ov dijagram logσ = σ (log N )
log N
logσ
σ
SR
σ A
σ D
N D
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Wöhler -ovi dijagrami epruvete i mašinskog dela
log N
logσ
σ SR
σ D
N D
σ DM
Epruveta
Mašinski deo
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log N
logσ
σ SR
σ D
N D
σ DM
Epruveta
Mašinski deo
Elastične deformacije
(veća osetljivost na koncentraciju napona)
Elastične i plastične deformacije (mala osetljivost na koncentraciju napona)
αk = 1
αk = 1
Wöhler -ovi dijagrami epruvete i mašinskog dela
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Wöhler -ovi dijagrami epruvete i mašinskog dela
σ DM ≤ σ D
1
AM
AD
K
Faktor dinamičke čvrstoće
log N
Mašinski deo
logσ
σ SR
σ D
N D
σ DM
Epruveta
log N
Mašinski deo
logσ
σ SR
σ D
N D
σ DM
logσ
σ SR
σ D
N D
σ DM
Epruveta
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Faktor dinamičke čvrstoće K D
221
k D
K
11 k k k
β k – efektivni faktor koncentracije napona
αk – teorijski (geometrijski) faktor koncentracije napona
ηk – faktor osetljivosti materijala na koncentraciju napona
ξ 1 – faktor veličine poprečnog preseka
ξ 2 – faktor stanja površine
ξ 3 – faktor koji uzima u obzir ostale uticaje (termička obrada, radna sredina i dr.)
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Wöhler -ov dijagram – radno stanje
log N
logσ
σ DM
N D
Rs
n
Oblast trajne dinamičke čvrstoće
σ g < σ DM n > N D
σ g σ SR
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Wöhler -ov i Smith-ov dijagram
Wöhler -ov dijagram: σ = f(N )
σ SR = const.
Smith-ov dijagram: σ D = f(σ SR )
σ SR = vario
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Smith-ov dijagram
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Smith-ov dijagram – čelik Č 0545
2D(-1)A
SR
2D(-1)
N/mm220
0
N/mm220
σ A=220
t t σ SR =0
σ A= 175
σ SR
σ N/mm2
σ D(-1)=220
2D(0)
ASR
2D(0)
N/mm1752
N/mm350
σ D(0)=350
σ N/mm2
σ SR = 175
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Smith-ov dijagram – čelik Č 0545
2D(-1)A
SR
2D(-1)
N/mm220
0
N/mm220
2D(0)
ASR
2D(0)
N/mm1752
N/mm350
σ D
σ
SR
I (σ SR ,σ D) = I (0,σ D(-1)) = I (0,220) II (σ SR ,σ D) = II (σ D(0)/2,σ D(0)) = II (175,350)
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Smith-ov dijagram – čelik Č 0545 I (σ SR ,σ D) = I (0,σ D(-1)) = I (0,220)
σ D
σ SR
Iσ D(-1) = 220
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Smith-ov dijagram – čelik Č 0545
II (σ
SR ,σ
D) = II (σ
D(0)/2,σ
D(0)) = II (175,350)σ D
σ SR
Iσ D(-1) = 220
I
σ D(0) = 350II
σ D(0)/2 = 175
σ SR = σ D(0)/2 = 175
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Smith-ov dijagram – čelik Č 0545
II (σ
SR ,σ
D) = II (σ
D(0)/2,σ
D(0)) = II (175,350)σ D
σ SR
Iσ D(-1) = 220
I
σ D(0) = 350II
σ D(0)/2 = 175
σ SR = σ D(0)/2 = 175
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Smith-ov dijagram – čelik Č 0545
σ D
σ SR
Iσ D(-1) = 220
I
σ D(0) = 350II
σ SR = σ D(0)/2 = 175
Epruveta
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Smith-ov dijagram mašinskog dela(čelik Č 0545, K D=2)
σ D
σ SR
Iσ D(-1) = 220
I
σ D(0) = 350II
σ SR = σ D(0)/2 = 175
Epruveta
1AM
AD
K
D
AAM
K
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I
Smith-ov dijagram mašinskog dela(čelik Č 0545, K D=2)
σ D
σ SR
Iσ D(-1) = 220
σ D(0) = 350II
σ SR = σ D(0)/2 = 175
Epruveta
1AM
AD
K
D
AAM
K
σ D(-1)M = 110
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Smith-ov dijagram mašinskog dela(čelik Č 0545, K D=2)
I
σ D
σ SR
Iσ D(-1) = 220
σ D(0) = 350II
σ SR = σ D(0)/2 = 175
Epruveta
σ D(-1)M = 110
1752
D(0)
A
1752
D(0)
SR
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Smith-ov dijagram mašinskog dela(čelik Č 0545, K D=2)
I
σ D
σ SR
Iσ D(-1) = 220
σ D(0) = 350II
σ SR = σ D(0)/2 = 175
Epruveta
σ D(-1)M = 110
σ D(0)M = 262,5 1752
D(0)
A
5,872
D
D(0)
D
AAM
K K
1752
D(0)
SR
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Smith-ov dijagram mašinskog dela(čelik Č 0545, K D=2 i K D=1,5)
σ SRσ SR = σ D(0)/2
σ D
σ D(-1)
σ D(0)
Epruveta
σ D(-1)M
σ
D(0)M
Mašinski deo (K D=2)
Mašinski deo (K D=1,5)
σ D(0)M
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Smith-ov dijagram mašinskog dela(čelik Č 0545, K D=2)
σ SRσ SR = σ D(0)/2
σ D
σ D(-1)
σ D(0)
Epruveta
σ D(-1)M
σ
D(0)M
Mašinski deo
αM
D(0)
1)D(
D
M 211
1tg
K
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Smith-ov dijagram – radno stanje Rs
σ D(-1)M
σ D(0)M
σ SR = const.
σ
SRσ
SR =const.
σ DMašinski deo
Rs
Rs
K σ DM
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Smith-ov dijagram – radno stanje Rs
σ SR / σ A = const.
σ D(-1)M
σ D(0)M
σ SR
σ DMašinski deo
Rs
Rs
K σ DM
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Smith-ov dijagram – radno stanje Rs
σ D(-1)M
σ d = 0
σ D(0)M
σ SR
σ DMašinski deo
Rs
Rs
K
σ DM
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Smith-ov dijagram – radno stanje Rs
σ D(-1)M
σ d = const.
σ D(0)M
σ SR
σ DMašinski deo
Rs
Rs
K
σ DM
σ d=const.