# rimeca

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2. ## "force controlled" and "displacement controlled" loadcases

Hi Prakash My problem happened while using Gauge Optim. So I guess size optimization will answer my question. Thank you,
3. ## "force controlled" and "displacement controlled" loadcases

Hi again Prakash, Any news concerning my question ? Have you tried to test a simple model and see the results? Thank you,
4. ## "force controlled" and "displacement controlled" loadcases

Thank you very much! I will wait for your answer and try the new formulation of the optimization probem you suggested. I am looking forward to hearing your feedback on the matter.
5. ## "force controlled" and "displacement controlled" loadcases

Hello Prakash, In case 2, I took the force that is induced by the enforced displacement ( through SPC Force ) and then imposed that and removed the enforced displacements ( SPC + SPCD ) I understand what you said about "having less material" leads to the part being more able to be displaced and that justifies the results found. But in this case does that mean this is correct mathematically but not really correct physically since this is not what we are really asking Optistruct to do ? Also, in my optimization problem, my objective function is mass that I want to minimize. Could using the compliance as objective function solve the problem ? Thank you very much for your help
6. ## "force controlled" and "displacement controlled" loadcases

Hello Prakash, Could you please read the other question I posted (with the same title) because it is the complete one. I was not able to delete the other one yesterday. To answer your question, I used a gauge optimization option where the thickness distribution is even.Thank you
7. ## "force controlled" and "displacement controlled" loadcases

Hello Prakash Pagadala × Could you please read this question because it is the complete one. I was not able to delete the other one yesterday. I used a gauge optimization option where the thickness distribution is even. Thank you
8. ## "force controlled" and "displacement controlled" loadcases

Hello all, I have a question about the equations behind the difference between loadcases that use forces vs loadcases that use enforced displacements. I am aware that these two loadcases lead to different results on Optistruct, but have found very few info in the help about it. I did a simple test watching the behaviour of a part under torsion and bending when I try to optimize it on Optistruct (minimize mass, Von Mises static constraints, gauge optimization). -When "enforced displacements" are used, we obtain a lighter part ( decrease of the thickness ) but the stresses decrease as well ! This is totally illogical since a decrease of the thickness should necessarily lead to an
9. ## "force controlled" and "displacement controlled" loadcases

Hello all, I have a question about the equations behind the difference between loadcases that use forces vs loadcases that use prescribed displacements. I am aware that these two loadcases lead to different results on Optistruct, but have found very few info in the help about it. I did a simple test watching the behaviour of a part under torsion and bending when I try to optimize it on Optistruct (minimize mass, Von Mises static constraints, gauge optimization). -When "enforced displacements" are used, we obtain a lighter part ( decrease of the thickness ) but the stresses decrease as well ! This is totally illogical since a decrease of the thickness should necessarily lead to an increase of the stresses. -When "forces" are used, we obtain a logical behaviour ( lighter final part with lower thickness but higher stresses ). Could anyone explain why the second model is right in this case ? And also is there a way to still use enforced displacements and get logical results. Thank you very much, P.S : the only help I found on Optistruct documentation about the matter is the following paragraph What is the difference between using forces and prescribed displacements? In order to increase stiffness, minimize compliance should be used with forces and maximize compliance with prescribed displacements. The compliance is defined as: Compliance ~ Force · Displacement When prescribed displacements are used, the reaction force must be increased to increase the stiffness. This means that the compliance has to be maximized. In case the forces are given, a stiffer structure means having lower displacements. To achieve this goal, the compliance needs to be minimized.
10. ## Compliance Response

Hello Merula, I know it has been two years you posted this message, but by any chance would you (or anyone else reading this) still have that file (http://www.trinity-eng.co.kr/ez/pdf/OptiStruct01.pdf) ? It seems the link doesn't work anymore. Also I am really interested in learning more in depth about the difference between "force controlled" or "enforced displacement controlled" load case and how the solver considers both cases. I tried to search a bit in Optistruct documentation but haven't found anything that talks about it. Thank you!
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