Optimizing the Threehole Model (Tosca Structure.gui)

The lowest natural frequency is to be maximized in this example without a change in volume.

  1. Define the first natural eigenfrequency in a Design Response (DRESP): 

    DRESP
	ID_NAME = DRESP_FREQ
	DEF_TYPE = SYSTEM
	TYPE = DYN_FREQ
	LC_SET = MODAL,ALL,1
	LC_SEL = MIN
	UPDATE = EVER
END_

  2. Reference the Design Response in the Objective Function (OBJ_FUNC): 

    OBJ_FUNC
	ID_NAME = MAXIMIZE_FREQ
	DRESP = DRESP_FREQ
	TARGET = MAX
END_

    Optimization where natural frequencies are to be maximized generally causes an increase of mass/volume and thus increasing the natural frequencies.

  3. To avoid an increase of volume, define a volume constraint as follows:

    1. Create a Design Response (DRESP) with the sum of all elements: 

      DRESP
	ID_NAME = DRESP_VOL_SHAPE
	DEF_TYPE = SYSTEM
	TYPE = VOLUME
	UPDATE = EVER
	EL_GROUP = ALL_ELEMENTS
	GROUP_OPER = SUM
END_

    2. Reference the Design Response in a constraint (CONSTRAINT):

      CONSTRAINT
	ID_NAME = volume_constraint
	DRESP = DRESP_VOL_SHAPE
	MAGNITUDE = REL
	EQ_VALUE = 1.0
END_

The result looks as follows:



The frequency development looks as follows: