Creeping of a tube under dead weight, pressure and axial load

acc. to Odqvist's invariants theory


This calculation is only a simplified estimation, and does not replace a detailed design calculation.


Input data
 Name   Value   Unit 
Outside diameter of the tube da mm
Tube wall thickness s mm
Tube length l mm
pi bar
pa bar
Axial force F kN
Lid force  
Tube temperature T(z) °C
Modulus of elasticity E N/mm²
Poissonīs ratio ν  
Density ρ kg/m³
Stress exponent n(T)1)  
Creep rate limit σc7(T)1) N/mm²
Creep constant k(T)1) MPa–n·h.–1
Creep constant C11) MPa–C2·h.–1
Creep constant C21)  
Creep constant C31) K
Operating duration t h.
Time step Δt h.


1) according to Nortonīs law:     dε / dt = k · σn,     k = 10–7 · σc7–n
or:     dε / dt = C1 · σC2 · e–C3/T
To enter are the following creep constants combinations:
    n and σc7, or n and k, or C1, C2 and C3