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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:

| (188)

where is the equivalent creep strain, 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:

- *CREEP
- Enter the LAW parameter and its value, if needed

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

- A.
- n.
- m.
- Temperature.

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=, n=5 and m=0 for T(temperature)=100. and A= and n=5 for T(temperature)=200.

Example files: beamcr.

Next: *CYCLIC HARDENING Up: Input deck format Previous: *COUPLED TEMPERATURE-DISPLACEMENT Contents