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Goal of this tutorial
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Relevant data for this tutorial:
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Step 1: MSC Nastran preperation
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EMENDATE_SERVICE_NASTRAN | C:\Program Files\MSC.Software\MSC_Nastran\2023.2\bin\nast20232.exe |
Path to your MSC Nastran installation |
Step 2: Open an already existing optimisation model / Set up a model as you are used to
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For this Tutorial a beam model is used. The model is already completely set-up (Design Space, Interfaces, Loads & Boundary Conditions, Material assignementassignment, optimisation parameters and static Events) for a static optimisation and in the following the Eigenfrequency Optimisation gets activated.
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Step 3: Advanced User Settings to initialize the Eigenfrequency Optimisation
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Event_1 is the static Event from which the BCs will be copied.
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Step 5: Starting the Optimisation
The optimisation can be started as usual. In the background MSC Nastran will be called to calculate the eigenfrequencies and eigenmodes.
Step 6: Post Processing
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Currently, the influence of the eigenfrequency calculation is displayed in the enveloped plot of the Failure Criterion (even if this isn’t based on a stress value).
To check the final eigenfrequencies of the part, please run a Re-Analysis with Apex structures.
Step 7: Creating Point Masses and using them for the Eigenfrequency Optimisation
Point masses play an important role in the calculation of eigenfrequencies. Therefore, Point Masses can be created with the Advanced User Settings.
A Point Mass can only be attached to surfaces where a Force is already applied to. The geometry name has to be linked correctly. Furthermore, the position has to be entered with three values (x,y,z) regarding the global coordinate system (These can be also reused from a remote force).
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Advanced User Settings to create a Point Mass:
pointMass.pointMass1.geometryName=ModelLoadEvent_Force_-_Moment_1 |
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Be aware that the Unit System in the Advanced User Settings is SI. Thus, you have to enter the position of the point in meters and the mass in kg! |
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Step 8: Modify the static load
If acceleration is used, this may result in loads being considered twice. Modify the Force to a very low value, thus the force is close to no impact. The acceleration acting on the Point Mass will automatically generate a static load.
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