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*CREEP

Keyword type: model definition, material

This option is used to define the creep properties of a viscoplastic material. There is one optional parameter LAW. Default is LAW=NORTON, the only other value is LAW=USER for a user defined creep law. The Norton law satisfies:


\begin{displaymath}
\dot{\epsilon} = A \sigma^n
\end{displaymath} (10)

where $\epsilon$ is the equivalent creep strain and $\sigma$ is the true Von Mises stress. For LAW=USER the creep law must be defined in user subroutine ucreep.f.

All constants may be temperature dependent. The card should be preceded by a *ELASTIC card within the same material definition, defining the isotropic elastic properties of the material. For LAW=NORTON the temperature data points under the *CREEP card must be the same as those under the *ELASTIC CARD. If a *PLASTIC card is defined within the same material definition, it should be placed after the *ELASTIC and before the *CREEP card. If no *PLASTIC card is found, a zero yield surface without any hardening is assumed.


First line:

Following lines are only needed for USER=NORTON (default): First line:

Use as many lines as needed to define the complete temperature dependence.

Example:

*CREEP
1.E-10,5.,100.
2.E-10,5.,200.

defines a creep law with A=$10^{-10}$ and n=5 for T(temperature)=100. and A= $2 \cdot 10^{-10}$ and n=5 for T(temperature)=200. The card must be preceded by an *ELASTIC card defining the elastic properties for exactly the same temperatures.


Example files: beamcr.


next up previous contents
Next: *CYCLIC HARDENING Up: Input deck format Previous: *CONTROLS   Contents
Guido Dhondt 2003-08-06