Maximizing the Eigenfrequency of a Certain Eigenmode

You can increase a specific eigenfrequency in the eigenfrequency spectrum belonging to a certain eigenmode. In this case, a specific eigenfrequency is defined using TYPE = DYN_FREQ.

This task shows you how to:

Before you begin:

When optimizing a specific eigenfrequency, the order of the eigenfrequencies might change during the optimization iterations. Consequently, the eigenfrequencies might must be tracked during the optimization iterations. This is done by mode tracking. For more information, see Mode Tracking.

See Also
Overview of Eigenfrequency
By default, the modes are not tracked during the optimization. Mode tracking is activated in OPT_PARAM command: 


DRESP
 ID_NAME      = single_lowest_eigenfrequency_1
 DEF_TYPE     = SYSTEM
 TYPE         = DYN_FREQ
 LC_SET       = MODAL, ALL, 1
END_
  
OBJ_FUNC
 ID_NAME      = maximize_single_eigenfrequency
 DRESP        = single_lowest__1
 TARGET       = MAX
END_
  
OPT_PARAM
 ID_NAME      = opt_params
 OPTIMIZE     = maximize_single_eigenfrequency
 MODETRACKING = ON
 MODENUMBERS  = 8
END_

For this example, at least 8 eigenfrequencies should be requested in the finite element input model defined by the user.

Define a Design Response for a Specific Eigenfrequency in Tosca Structure.gui

  1. To create a new Design Response, select Command > DRESP.
    The DRESP dialog appears.
  2. Set DefType = System, Category = Base and Type = DYN_FREQ.
  3. Choose the load case by clicking Add LC and setting Analysis Type to MODAL, entering the load case ID and the numbers of eigenmodes (for example, 1) in the Eigenmode/Subcase field.