model creep command

Syntax

model creep keyword

Primary keywords:

active    time-total    list    slave    substep    timestep

Set parameters for a creep material analysis. Time-dependent creep material analysis is only available if model configure creep has been specified. This is only available with the Creep model option — see Creep Model Option preceding should be a link for details. [CS: this is another common docs, many codes issue]

active b

The creep process is on, by default, when the model configure creep command is given. Specify active off to suppress the creep calculation.

time-total f

f is the accumulated creep time for the model. This can be reset to any value, and will continue to be accumulated during cycling after that.

list

Display creep calculation-mode information.

slave b

Specifies that creep mode is to be considered a slave, and cycled to equilibrium after each master step has been taken. This particular option is provided for completeness, but is rarely useful in creep calculations.

substep i

Specifies the maximum number of steps the creep process will take when solving with slave on.

timestep

Timestep controls for creep calculations. Note that there is no analytical solution for the stable timestep for most creep models, therefore the timestep in automatic mode is controlled by a servo tied to the unbalanced force ratio. [CS: removing this for now while we are on PFC; common docs issue] See the topic ref-automaticadjustmentofthecreeptimestep- in the Creep section. The following keywords are available.

automatic b

If on, the stable timestep is determined according to the timestep servo with settings specified below. If off the timestep must be set manually using the fix keyword.

fix f

Set the timestep to be the fixed value f. All timestep calculations are skipped.

Warning

Using the fix keyword may result in model instabilities if f is above the stable timestep limit. Use this with extreme caution.

increment f

Set the incremental amount that the timestep is allowed to increase from one cycle to the next in automatic mode. By default, f = 1.05. The timestep can decrease by any amount to ensure stability.

latency i

Set the minimum number of steps that must elaspe before the timestep is changed when the servo is controlling the timestep. Using this keyword implicitly sets servo on. By default the :latency: is 1.

lower-bound f

If the current convergence ratio falls below f, then the lower-multiplier is applied to the time step to increase it. Using this keyword implicitly sets servo on. By default the :lower-bound: is 1e-3.

lower-multiplier f

The value applied to the current timestep when the convergence ratio falls below lower-bound. This value should be greater than 1.0. By default lower-multiplier is 1.01.

maximum f

The maximum timestep allowed. The servo will not raise the timestep above this value. There is no default timestep maximum.

minimum f

The minimum timestep allowed. The servo will not lower the timestep below this value. There is no default timestep minimum.

servo b

Activate or de-activate the timestep servo control. If the timestep has been set to automatic on and servo off, then the last calculated servo value will continue to be used.

starting f

Specify the timestep to use at the start of creep calculations, when the timestep is under servo control. The timestep will be adjusted by the servo every step afterwards. A starting timestep must be given before starting creep calculations.

unbalanced b

Indicate that the timestep servo is to use maximum unbalanced force instead of the convergence ratio. The values lower-bound and upper-bound are now compared against the maximum unbalanced force. Note that the default values of lower-bound and upper-bound are unlikely to be valid for this case.

upper-bound f

If the current convergence ratio falls above f, then the upper-multiplier is applied to the time step to increase it. Using this keyword implicitly sets servo on. By default the :upper-bound: is 5e-3.

upper-multiplier f

The value applied to the current timestep when the convergence ratio falls above upper-bound. This value should be less than 1.0. By default lower-multiplier is 0.9.