Femap and Accel1 Nastran cards

Femap and Accel1 Nastran cards

Working with ACCEL1 cards?  Getting NX Nastran fatal SYSTEM FATAL MESSAGE 3094 (SSGSLT)?

Femap recently came out with support with ACCEL1 cards.  This started with v11.2.  Nastran ACCEL1 cards are great for applying localized nodal acceleration as a boundary condition.  Alternatively, GRAV cards (body acceleration) can be used, but they have a limitation of universal application to every node in your model.  With an ACCEL1 card, you could just apply an acceleration to a single node, for example.  A benefit to this is being able to prescribe different accelerations for different parts in your model.  An isolated electronics box might not see the acceleration magnitude, for example, of an unisolated box sitting next to it in a dynamic environment.

There is an important caveat to note with ACCEL1 cards.  Femap will write 1 card per node by default.  If you have > 10k nodes with ACCEL1 , Nastran will bomb (doesn’t support it – don’t know why but this limitation exists).  Add the following to your FEMAP.INI file:

[User]

WriteCompactAccel1=1

This will force Femap to combine nodes onto the same ACCEL1 cards, producing fewer cards and hopefully staying under the 10k ACCEL1 card limit.  The last change to NX Nastran that I know was for V9.0, which was upgraded to support up to 10000 ACCEL1 cards with the same SID.

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