Creeping of a tube under dead weight, pressure and axial load
in acc. to Odqvist's invariants theory
Attention!
This calculation is only a simplified estimation and does not replace a detailed design calculation.
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Input data
Name
Value
Unit
Outside diameter of the tube
d
a
mm
Tube wall thickness
s
mm
Tube length
l
mm
p
i
bar
p
a
bar
Axial force
F
kN
Lid force
no
yes
Tube temperature
T
(z)
°C
Material
Sandvik 253MA
Carbon steel
Chrom steel
Stainless steel
Nimonic 75
Duralumin 24 S-T 4
Al. All. RR-59
Copper
Mg. All.
Modulus of elasticity
E
N/mm²
Poissonīs ratio
ν
Density
ρ
kg/m³
Stress exponent
n
(T)
1)
Creep rate limit
σ
c7
(T)
1)
N/mm²
Creep constant
k
(T)
1)
MPa
–n
·h.
–1
Creep constant
C
1
1)
MPa
–C
2
·h.
–1
Creep constant
C
2
1)
Creep constant
C
3
1)
K
Operating duration
t
h.
Time step
Δt
h.
1)
according to Nortonīs law:
dε / dt = k · σ
n
,
k = 10
–7
· σ
c7
–n
or:
dε / dt = C
1
· σ
C
2
·
e
–C
3
/T
To enter are the following creep constants combinations:
n
and
σ
c7
, or
n
and
k
, or
C
1
,
C
2
and
C
3