Training:

Relevant data for this tutorial:

Step 1: MSC Nastran preperation

To be able to use the Eigenfrequency Optimisation a MSC Nastran version with a valid license must be installed on the same machine.

The environment variable has to be set once manually:

EMENDATE_SERVICE_NASTRAN

C:\Program Files\MSC.Software\MSC_Nastran\2023.2\bin\nast20232.exe

Step 2: Open an already existing optimisation model / Set up a model as you are used to

The Eigenfrequency Optimisation is activated additionally to static events. Thus, you can set up your model as every other optimisation and before you start the optimisation the Eigenfrequency Optimisation gets activated with the Advanced User Settings.

For this Tutorial a beam model is used. The model is already completely set-up (Design Space, Interfaces, Loads & Boundary Conditions, Material assignement, optimisation parameters and static Events) for a static optimisation and in the following the Eigenfrequency Optimisation gets activated.

Step 3: Advanced User Settings to initialize the Eigenfrequency Optimisation

The following 3 Advanced User Setting commands are mandatory to start a Eigenfrequency Optimisation. With these a additional event for the Eigenfrequencies is added.

event.EventFA.strategy=conditionBasedFrequencyAnalysis

event.EventFA.frequencyTarget=210

event.EventFA.safetyFactor=1

The Frequency Target (in Hz) is the target for the first occurring eigenfrequency of the part. This value need to be adjusted to your according requirements of the part.

As an optional input the range and the number of frequencies which are taken into account for the optimisation can be modified. By default the first 10 eigenmodes are considered to an upper frequency limit of 3 times the frequency target.

event.EventFA.frequencyMax=4500
event.EventFA.frequencyCount=10

Step 4: Advanced User Settings to copy Boundary Conditions from an already existing Event

Since the Eigenfrequency Optimisation isn’t integrated into the GUI yet, Boundary Conditions (Fixations) can be copied from a static event. Therefore, the following command needs to be added:

event.EventFA.condition.\.include = event.Event_1.condition

Event_1 is the static Event from which the BCs will be copied.

Step 5: Starting the Optimisation

Step 6: Post Processing

Step 7: Creating Point Masses and using them for the Eigenfrequency Optimisation

Advanced User Settings to create a Point Mass:

pointMass.pointMass1.geometryName=ModelLoadEvent_Force_-_Moment_1
pointMass.pointMass1.x=0.87468
pointMass.pointMass1.y=0.625685
pointMass.pointMass1.z=0.33058
pointMass.pointMass1.type=RBE3
pointMass.pointMass1.mass=1