Topology optimization: entire design volume disappears
Topology optimization: entire design volume disappears
(OP)
Hello,
I want to do a topology optimization on a design volume with 3 other volumes being non-design volumes. All loads and constraints being on the non-design volumes. However I seem to be running into a problem setting up my optimization, I would be most grateful to get some help.
I setup my model in hyperworks and was able to get my results to show on Radioss so I suppose my meshing, loads and constraints have been properly setup.
I setup my optimization as following:
Design variable: PSOLID referencing to the Property I want to be the design volume, which is also PSOLID.
Optimization response: Volume Total
Objective: min / response = volume (my optimization response)
However after running Optistruct and looking at the results in Hyperview I see that the design volume is entirely empty starting from the first iteration and for the following 12 iterations.
Also, my output file shows that there seems to be a difference in volume between each iteration, I do not see the link between what is written there and what's shown in Hyperview:
------------------------------------------------------------------------------
Element Property # of Recommended Range Max. Viol. Elem.
Viol. Lower Upper Value type No.
------- ------------------- -------- --------- --------- --------- --- -------
TETRA Edge Angle 16 -- 75.00 81.50 U 86159
(Scratch disk space usage for starting iteration = 19 MB)
(Running in-core solution)
Objective Function (Minimize VOLUM) = 6.49221E-03
No active constraints
Design Volume Fraction = 9.00000E-01 Mass = 1.75290E+01
Subcase Compliance
1 4.525657E-04
RETAINED RESPONSES TABLE
------------------------------------------------------------------------------------
Response Type Response Subcase Grid/ DOF/ Response Objective Viol.
User-ID Label /Frqncy Element/ Comp Value Reference/ %
MID/PID/ /Reg Constraint
Mode No. Bound
------------------------------------------------------------------------------------
1 VOLUM volume -- -- TOTL 6.492E-03 MIN
------------------------------------------------------------------------------------
ITERATION 1
Objective Function (Minimize VOLUM) = 4.67824E-03 % change = -27.94
No active constraints
Design Volume Fraction = 6.00000E-01 Mass = 1.26312E+01
Subcase Compliance
1 4.718218E-04
RETAINED RESPONSES TABLE
------------------------------------------------------------------------------------
Response Type Response Subcase Grid/ DOF/ Response Objective Viol.
User-ID Label /Frqncy Element/ Comp Value Reference/ %
MID/PID/ /Reg Constraint
Mode No. Bound
------------------------------------------------------------------------------------
1 VOLUM volume -- -- TOTL 4.678E-03 MIN
------------------------------------------------------------------------------------
ITERATION 2
Objective Function (Minimize VOLUM) = 2.86427E-03 % change = -38.77
No active constraints
Design Volume Fraction = 3.00000E-01 Mass = 7.73353E+00
Subcase Compliance
1 6.865162E-04
RETAINED RESPONSES TABLE
------------------------------------------------------------------------------------
Response Type Response Subcase Grid/ DOF/ Response Objective Viol.
User-ID Label /Frqncy Element/ Comp Value Reference/ %
MID/PID/ /Reg Constraint
Mode No. Bound
------------------------------------------------------------------------------------
1 VOLUM volume -- -- TOTL 2.864E-03 MIN
------------------------------------------------------------------------------------
ITERATION 3
Objective Function (Minimize VOLUM) = 1.95728E-03 % change = -31.67
No active constraints
Design Volume Fraction = 1.50000E-01 Mass = 5.28467E+00
Subcase Compliance
1 1.495673E-03
Thank you very much for your help,
Hugo
I want to do a topology optimization on a design volume with 3 other volumes being non-design volumes. All loads and constraints being on the non-design volumes. However I seem to be running into a problem setting up my optimization, I would be most grateful to get some help.
I setup my model in hyperworks and was able to get my results to show on Radioss so I suppose my meshing, loads and constraints have been properly setup.
I setup my optimization as following:
Design variable: PSOLID referencing to the Property I want to be the design volume, which is also PSOLID.
Optimization response: Volume Total
Objective: min / response = volume (my optimization response)
However after running Optistruct and looking at the results in Hyperview I see that the design volume is entirely empty starting from the first iteration and for the following 12 iterations.
Also, my output file shows that there seems to be a difference in volume between each iteration, I do not see the link between what is written there and what's shown in Hyperview:
------------------------------------------------------------------------------
Element Property # of Recommended Range Max. Viol. Elem.
Viol. Lower Upper Value type No.
------- ------------------- -------- --------- --------- --------- --- -------
TETRA Edge Angle 16 -- 75.00 81.50 U 86159
(Scratch disk space usage for starting iteration = 19 MB)
(Running in-core solution)
Objective Function (Minimize VOLUM) = 6.49221E-03
No active constraints
Design Volume Fraction = 9.00000E-01 Mass = 1.75290E+01
Subcase Compliance
1 4.525657E-04
RETAINED RESPONSES TABLE
------------------------------------------------------------------------------------
Response Type Response Subcase Grid/ DOF/ Response Objective Viol.
User-ID Label /Frqncy Element/ Comp Value Reference/ %
MID/PID/ /Reg Constraint
Mode No. Bound
------------------------------------------------------------------------------------
1 VOLUM volume -- -- TOTL 6.492E-03 MIN
------------------------------------------------------------------------------------
ITERATION 1
Objective Function (Minimize VOLUM) = 4.67824E-03 % change = -27.94
No active constraints
Design Volume Fraction = 6.00000E-01 Mass = 1.26312E+01
Subcase Compliance
1 4.718218E-04
RETAINED RESPONSES TABLE
------------------------------------------------------------------------------------
Response Type Response Subcase Grid/ DOF/ Response Objective Viol.
User-ID Label /Frqncy Element/ Comp Value Reference/ %
MID/PID/ /Reg Constraint
Mode No. Bound
------------------------------------------------------------------------------------
1 VOLUM volume -- -- TOTL 4.678E-03 MIN
------------------------------------------------------------------------------------
ITERATION 2
Objective Function (Minimize VOLUM) = 2.86427E-03 % change = -38.77
No active constraints
Design Volume Fraction = 3.00000E-01 Mass = 7.73353E+00
Subcase Compliance
1 6.865162E-04
RETAINED RESPONSES TABLE
------------------------------------------------------------------------------------
Response Type Response Subcase Grid/ DOF/ Response Objective Viol.
User-ID Label /Frqncy Element/ Comp Value Reference/ %
MID/PID/ /Reg Constraint
Mode No. Bound
------------------------------------------------------------------------------------
1 VOLUM volume -- -- TOTL 2.864E-03 MIN
------------------------------------------------------------------------------------
ITERATION 3
Objective Function (Minimize VOLUM) = 1.95728E-03 % change = -31.67
No active constraints
Design Volume Fraction = 1.50000E-01 Mass = 5.28467E+00
Subcase Compliance
1 1.495673E-03
Thank you very much for your help,
Hugo





RE: Topology optimization: entire design volume disappears
Cheers
Greg Locock
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RE: Topology optimization: entire design volume disappears
Created RAM scratch area: total size 200.00 MB
INFORMATION # 742
The dependent rotational d.o.f. of this rigid element is removed.
RBE2 element id = 4035
independent grid id = 2656
a dependent grid id = 1772
This is because there is no need to constrain the rotational d.o.f. of
any of the dependent grids.
INFORMATION # 742
The dependent rotational d.o.f. of this rigid element is removed.
RBE2 element id = 4036
independent grid id = 2656
a dependent grid id = 1731
This is because there is no need to constrain the rotational d.o.f. of
any of the dependent grids.
INFORMATION # 742
The dependent rotational d.o.f. of this rigid element is removed.
RBE2 element id = 4037
independent grid id = 2656
a dependent grid id = 1690
This is because there is no need to constrain the rotational d.o.f. of
any of the dependent grids.
INFORMATION # 743
The total number of rigid elements, whose rotational dependent d.o.f.
are removed because there is no need to constrain those d.o.f., is 89
ERROR # 110 FROM SUBROUTINE preprbe2
The dependent d.o.f. is constrained by grid or spc data.
RBE2 element id = 4040
grid id = 1770
component = 1
***** FATAL INPUT ERROR *****
ERROR # 110 FROM SUBROUTINE preprbe2
The dependent d.o.f. is constrained by grid or spc data.
RBE2 element id = 4080
grid id = 1605
component = 2
***** FATAL INPUT ERROR *****
RE: Topology optimization: entire design volume disappears
I also tried it with a displacement constraint, but still got a empty design volume from the first iteration.
RE: Topology optimization: entire design volume disappears
The error message you seen when going through the tutorial is mostly likely caused by placing a constraint on the dependent node of an RBE2.
RE: Topology optimization: entire design volume disappears
I uploaded my carm example on rapidshare if anyone finds it simpler to find the mistake that way:
http:
Furthermore the I uploaded my own problem at:
htt
Also about contacting support, should I contact them at:
ht
I am not sure if it is okay for me as it seems to be more of a problem with my own Hypermesh skills than a software problem.
Thank you for answering!
Hugo
RE: Topology optimization: entire design volume disappears
I found out that when implementing my displacement constraint I had forgotten to link it to my loadstep. Once I linked it my model worked.
If anyone reads this with the same problem, my model did not work without a displacement variable and constraint.
RE: Topology optimization: entire design volume disappears