Using the VOID command on a structural area

I am trying to model a plate. I want the edges of the plate to be thicker than the center of the plate.
First i am constructing the outer geometry of the plate with this code:

!*! Structural area
SAR 1 MNO 1 GRP 1 NX 0 0 1 T #T QREF BELO ! Definition of the plate (if edge beam, QREF BELO)
loop#i #no_edges-1 ! Loop through all edges of the plate saved in CDB
SARB TYPE OUT NA 1+#i NE 2+#i ! Define each edge
endloop ; SARB TYPE OUT NA 1+#i NE 1 ! Tie the last node to the first one
GRP 1 titl ‘Plate’ ! Name the group

It works perfectly fine. Then i am defining the nodes of the edges with thicker plate - it also works fine. But in the loop were im trying to void the defined plate area, it does not void. It just creates two meshes on top of each other.
Does anyone have a reason why, or how to fix it?

!*! Add edge beam to model
SPT 9001 X #xmin Y #ymin
SPT 9002 X #xmin Y #ymin+2.5
SPT 9003 X #xmax Y #ymin+2.5
SPT 9004 X #xmax Y #ymin

SPT 9005 X #xmin Y #ymax-2.5
SPT 9006 X #xmin Y #ymax
SPT 9007 X #xmax Y #ymax
SPT 9008 X #xmax Y #ymax-2.5

loop#j 2 ! First loop cuts an opening, second adds a new SAR.
if #j == 0
SAR VOID ! Cut opening
SAR 9500 MNO 1 GRP 4 NX 0 0 1 T 550 QREF BELO ! Define new SAR

    SARB TYPE OUT NA 9001  NE 9002 ! Node 1 of edgebeam
    SARB TYPE OUT NA 9002  NE 9003 ! Node 2 of edgebeam
    SARB TYPE OUT NA 9003  NE 9004 ! Node 3 of edgebeam
    SARB TYPE OUT NA 9004  NE 9001 ! Node 4 of edgebeam

    if #j == 0
        SAR VOID ! Cut opening
        SAR 9600 MNO 1 GRP 4 NX 0 0 1 T 550 QREF BELO  ! Define new SAR

    SARB TYPE OUT NA 9005  NE 9006 ! Node 1 of edgebeam
    SARB TYPE OUT NA 9006  NE 9007 ! Node 2 of edgebeam
    SARB TYPE OUT NA 9007  NE 9008 ! Node 3 of edgebeam
    SARB TYPE OUT NA 9008  NE 9005 ! Node 4 of edgebeam


Few caveats:

  • The intent of Void and Prop, as I have understood it, is to take a large SAR and change patches of that SAR.
    It has worked very poorly for me, when trying to create openings/changing properties across several SARs.
    I believe that the opening/property change works best if there are “edges” of the original SAR left around the hole/property change.

  • From what I can read in your code you are:
    1: Creating Boundaries/Edges
    2: Placing Points (SPTs) at the boundary ends
    3: Using the points to define the SAR boundaries (SARB)
    This means you under the hood are:
    1: Create nodes and connect them with lines
    2: Naming/overwriting the end points of the lines
    3: Creating SAR boundaries by connecting the points
    A much cleaner/logical way would be:
    1: Create SPTs (SPT NO xxx )
    2: Create SLNs using the SPTs (SLN NO yyy NPA xxx1 NPE xxx2)
    3: Create SARs using the SLNs (SAR NO zzz; SARB NL yyy1, yyy2,... )

  • It’s hard to say why your code fails with just the snippet.
    However, you might want to consider defining your original SAR with inner openings from the start (SARB TYPE IN).
    Then “fill in” the holes with new SARs.
    This should always work. As an added benefit all SARs are clearly numbered (and accessible for e.g. secondary groups)

I have also been thinking that this is the problem.

You are right about what i am trying to achieve. I have also tried doing the cleaner way, where i define the plate as one SAR, and edgebeams as a different SAR - when running the model i get large displacements. Is there some code that connects the SARs to eachother, so i dont get large rotations/displacement? It seems like the edge beams are not connected to the plate SAR.

What is the difference between inner openings (SARB TYPE IN) and outer openings (SARB TYPE OUT), other than inner and outer geometry?

Thanks for your answer!

  • SarB Type Out Outer perimeter of the area you are creating
  • SarB Type In Holes/openings of the area you are creating

You don’t have to connect SARs explicitly. If they have a mutual boundary/edge, they should connect automatically:

  • Make sure you are not specifying a XFLG option under SPT/SLN/SAR
  • If you define SPTs twice with different numbers, two unconnected nodes are created. The same goes for SLNs. → Make sure you define mutual points/lines only once if you are numbering them.

Thank you very much for your time.