Keyword type: step
With *OBJECTIVE one can define the objective functions in a sensitivity analysis. Right now the following objectives are allowed for TYPE=COORDINATE design variables:
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where is the von Mises stress in node i,
and
are user-defined parameters. The higher
the closer
is to the actual
maximum (a value of 10 is recommended; the higher this value, the sharper the
turns in the function).
is the target stress, it
should not be too far
away from the actual maximum.
and for TYPE=ORIENTATION design variables:
Optional parameters are FILTER and RADIUS. Filtering smoothes the sensitivity results across the surface. This is especially needed for quadratic elements (such as C3D20 or C3D10), for which a checkerbord pattern arises if no smoothing is applied. The filter is a pyramid-type function with a radius specified by the parameter RADIUS (unit of length). Using the parameter FILTER automatically requires the parameter RADIUS.
First line:
Second line:
The objective functions SHAPEENERGY, MASS, DISPLACEMENT and STRESS require a *STATIC step before the *SENSITIVITY step, the objective function EIGENFREQUENCY requires a *FREQUENCY step immediately preceding the *SENSITIVITY step and the objective function GREEN requires a *GREEN step before the *SENSITIVITY step. Therefore, the {SHAPEENERGY, MASS, DISPLACEMENT, STRESS} objective functions, the {EIGENFREQUENCY} objective function and the {GREEN} objective function are mutually exclusive within one and the same *SENSITIVITY step.
Example: *OBJECTIVE,FILTER,RADIUS=3. DISPLACEMENT,N1
defines the sum of the square of the displacements in set N1 to be the objective function. The sensitivities will be smoothed using a filter with a radius equal to 3 length units.
Example files: sensitivity_I.