Free Size ignores max displacement

Altair Forum User

Hello,

 

I'm currently trying to optimize the laminate of a cfk part with the free sizing optimization. 
At the end of the run it states 'OPTIMIZATION HAS CONVERGED' 'FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED)' but the programm is just reducing the mass while the displacement constantly gets bigger and is far bigger than the max displacement constraint I set for the optimization.

 

Iteration Subcase     Variable  Grid/Elem ID   Value
---------------------------------------------------------
    0      1 MaxDisp                  1350_Y -10.6306
    0      0 ObjFun:MinimizeMASS         0    5.14431e-005
    0      0 MaxConstrViol(%)            0    0
    1      1 MaxDisp                  1350_Y -15.9459
    1      0 ObjFun:MinimizeMASS         0    3.42954e-005
    1      0 MaxConstrViol(%)            0    0
    2      1 MaxDisp                  1350_Y -31.8917
    2      0 ObjFun:MinimizeMASS         0    1.71477e-005
    2      0 MaxConstrViol(%)            0    0
    3      1 MaxDisp                  1350_Y -63.7835
    3      0 ObjFun:MinimizeMASS         0    8.57385e-006
    3      0 MaxConstrViol(%)            0    0
    4      1 MaxDisp                  1350_Y -97.4669
    4      0 ObjFun:MinimizeMASS         0    5.61036e-006
    4      0 MaxConstrViol(%)            0    0
    5      1 MaxDisp                  1344_Y -101.241
    5      0 ObjFun:MinimizeMASS         0    5.49722e-006
    5      0 MaxConstrViol(%)            0    0
    6      1 MaxDisp                  1344_Y -101.581
    6      0 ObjFun:MinimizeMASS         0    5.49262e-006
    6      0 MaxConstrViol(%)            0    0
    7      1 MaxDisp                  1344_Y -101.581
    7      0 ObjFun:MinimizeMASS         0    5.49262e-006
    7      0 MaxConstrViol(%)            0    0

 

The total displacement constraint is set to -2mm.

Min ply thickness is set to 2mm and max 50mm.

Altair Forum User

Hi,

 

Can you share the entire .out file, please?

 

Is the -2 set to lower bound or upper bound?

Altair Forum User

Hi @lngsfrdr

 

Thank you for sharing the .out file. I can see from the .out file that you have included displacement constraints. 

 

But is the displacement constraint directional or absolute magnitude?

 

Looks like you have applied a total displacement constraint on nodes and not directional. 

Altair Forum User

Hello and thank you for your quick response!

When I set it to a directional displacement it states 'INFEASIBLE DESIGN (AT LEAST ONE CONSTRAINT VIOLATED)' because the displacement doesn't get any smaller than ~4mm but it keeps reducing the weight instead of adding plies.

I will upload the new .out file

Altair Forum User

Ok I think I was able to fix it. I thickened up the plies until i got a displacement less than 2 mm in the analysis run. 
When I optimize the 'oversized' laminate it reduced the ply thickness as much as possible.

Altair Forum User

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