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*CONTROLS
Keyword type: step
This option is used to change the iteration control parameters. It
should only be used by those users who know what they are doing and
are expert in the field. There are two, mutually exclusive
parameter: PARAMETERS and
RESET. The RESET parameter resets the control parameters to their
defaults. With the parameter PARAMETERS is used to change the
defaults. It can take the value TIME INCREMENTATION, FIELD or LINE SEARCH. If the TIME INCREMENTATION value is
selected, the number of iterations before certain actions are taken
(e.g. the number of divergent iterations before the increment is
reattempted) can be changed and effect of these actions (e.g. the
increment size is divided by two). The FIELD parameter can be used to
change the convergence criteria themselves.
Finally, LINE SEARCH
can be used to change the line search parameters (only for face-to-face
penalty contact). The line search parameter scales the correction to the
solution calculated by the Newton-Raphson algorithm such that the residual
force is orthogonal to the correction. This requires the solution of a
nonlinear equation, and consequently an iterative procedure. In CalculiX this
procedure is approximated by a linear connection between:
- the scalar product of the residual force from the last iteration with
the solution correction in the present iteration (corresponds to a line
search parameter of zero) and
- the scalar product of the residual force in the present iteration with
the solution correction in the present iteration (corresponds to a line
search parameter of one).
For details of the line seach algorithm the reader is referred to [78].
First line:
- *CONTROLS
- Enter the PARAMETERS parameter and its value, or the RESET parameter.
There are no subsequent lines if the parameter RESET is selected.
Following lines if PARAMETERS=TIME INCREMENTATION is selected:
Second line:
iteration after which a check is made whether the
residuals increase in two consecutive iterations (default: 4). If so,
the increment is reattempted with
times its size.
iteration after which a logarithmic convergence check is
performed in each iteration (default: 8). If more than
iterations are needed, the increment is reattempted with
its size.
iteration after which the residual tolerance
is used
instead of
(default: 9).
maximum number of iterations allowed (default: 16).
number of iterations after which the size of the
subsequent increment will be reduced (default: 10).
maximum number of iterations allowed in two consecutive
increments for the size of the next increment to be increased
(default: 4).
Currently not used.
Maximum number of cutbacks per increment (default: 5). A
cutback is a reattempted increment.
Currently not used.
Currently not used.
Third line:
Cutback factor if the solution seems to diverge(default: 0.25).
Cutback factor if the logarithmic extrapolation predicts
too many iterations (default: 0.5).
Cutback factor for the next increment if more than
iterations were needed in the current increment (default: 0.75).
Cutback factor if the temperature change in two subsequent
increments exceeds DELTMX (default: 0.85).
Currently not used.
Currently not used.
Factor by which the next increment will be increased if
less than
iterations are needed in two consecutive increments (default: 1.5).
Currently not used.
Following lines if PARAMETERS=FIELD is selected:
Second line:
-
Convergence criterion for the ratio of the largest
residual to the average force (default: 0.005). The average force is
defined as the average over all increments in the present step of the
instantaneous force. The instantaneous force in an increment is
defined as the mean of the absolute value of the nodal force
components within all elements.
-
Convergence criterion for the ratio of the largest
solution correction to the largest incremental solution value (default: 0.01).
-
Initial value at the start of a new step of the
time average force (default:
the time average force from the previous steps or 0.01 for the first step).
-
user-defined average force. If defined, the
calculation of the average force is replaced by this value.
-
Alternative residual convergence criterion to be
used after
iterations instead of
(default: 0.02).
-
Criterion for zero flux relative to
(default:
).
-
Convergence criterion for the ratio of the
largest solution correction to the largest incremental solution value
in case of zero flux (default:
).
-
Convergence criterion for the ratio of the largest
residual to the average force for convergence in a single iteration (default:
).
Following lines if PARAMETERS=LINE SEARCH is selected:
Second line:
- not used.
-
Maximum value of the line search parameter (default: 1.).
-
Minimum value of the line search parameter (default: 0.25).
- not used.
- not used.
Example:
*CONTROLS,PARAMETERS=FIELD
1.e30,1.e30,0.01,,0.02,1.e-5,1.e-3,1.e-8
leads to convergence in just one iteration since nearly any residuals
are accepted for convergence (
and
.
Example files: beammrco.
Next: *COUPLED TEMPERATURE-DISPLACEMENT
Up: Input deck format
Previous: *CONTACT PRINT
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guido dhondt
2016-03-08