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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:

$\displaystyle \dot{\epsilon} = A \sigma^n t^m$ (188)

where $ \epsilon$ is the equivalent creep strain, $ \sigma$ is the true Von Mises stress an t is the total time. For LAW=USER the creep law must be defined in user subroutine creep.f.

All constants may be temperature dependent. The card should be preceded by a *ELASTIC card within the same material definition, defining the elastic properties of the material. If for LAW=NORTON the temperature data points under the *CREEP card are not the same as those under the *ELASTIC card, the creep data are interpolated at the *ELASTIC temperature data points. 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.

If the elastic data is isotropic, the large strain viscoplastic theory treated in [58] and [59] is applied. If the elastic data is orthotropic, the infinitesimal strain model discussed in Section 6.7.9 is used. If a *PLASTIC card is used for an orthotropic material, the LAW=USER option is not available.


First line:

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

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

Example:

*CREEP
1.E-10,5.,0.,100.
2.E-10,5.,0.,200.

defines a creep law with A=$ 10^{-10}$, n=5 and m=0 for T(temperature)=100. and A= $ 2 \cdot 10^{-10}$ and n=5 for T(temperature)=200.


Example files: beamcr.


next up previous contents
Next: *CYCLIC HARDENING Up: Input deck format Previous: *COUPLED TEMPERATURE-DISPLACEMENT   Contents
guido dhondt 2012-10-06