## *SENSITIVITY

Keyword type: step

This procedure is used to perform a sensitivity analysis. There are three optional parameters: NLGEOM, READ and WRITE. If NLGEOM is active, the change of the stiffness matrix w.r.t. the design variables is performed based on:

• a material tangent stiffness matrix at the strain at the end of the previous static step
• displacements at the end of the previous static step (large deformation stiffness)
• the stresses at the end of the previous static step (stress stiffness)

It makes sense to include NLGEOM if it was used on a previous static step and not to include it if it was not used on a prevous static step or in the absense of any prevous static step.

The parameters READ and WRITE are mutually exclusive and can only be used if the coordinates are the design variables. If WRITE is selected, the “raw” sensitivities (i.e. without filtering or any other action defined underneath the *FILTER card) for all design nodes are stored in file jobname.sen in ascending order of the design node numbers. If READ is selected the raw sensitivities are read from file jobname.sen. They can be further processed by filtering etc.

Notice that the objective functions STRAIN ENERGY, MASS, ALL-DISP and STRESS require a previous *STATIC step, the objective GREEN requires a previous *GREEN step and the objective EIGENFREQUENCY requires a previous *FREQUENCY step, possibly preceded by a *STATIC step, cf. *OBJECTIVE.

First line:

• *SENSITIVITY
• Enter the NLGEOM parameter if needed.

Example:

*SENSITIVITY


defines a linear sensitivity step.

Example files: beampic, beampis.