Model enforced displacement + force

Altair Forum User

Hi all,

 

 

 

 

I am trying to model a combined enforced displacement (with a SPCD) + an applied force. However I could only model it separetly and all the examples I find in the web are about modelling only a enforced displacement or only a force but not both combined. Could anybody help me with this?

 

 

 

 

 

Thanks a lot,

 

 

 

 

 

Regards,

 

 

 

 

 

Mario

 

Altair Forum User

Hi Mario,

 

Usually LOAD or LOADADD is the solution to have load combination. But this does not support Adding SPCD.

 

could you please let me know what the use case is and what is the analysis about?

Altair Forum User

I am working on DaCM topology optimization problem. I gave fixed supports to left top and bottom corners of thin square plate, enforced displacement in +x direction on midpoint of right edge. For this, I used SPC and SPCD load type - assigned loadcase as SPC. Then applied horizontal point load on midpoint of left edge and assigned loadcase as Load.

 

vol frac - 0.35, obj is to min compliance.

 

Shows Error 318 -  static load case has non zero applied loads & prescribed displacements. Optimization with compliance can not be performed.

 

Please help. Thanks !

tinh

Hi,

if there is no solution for load combination

why don't you apply enforced-disp directly to SPC (not use SPCD)?

i think it is a workaround for your case. But please verify results

example:

Unable to find an attachment - read this blog

Altair Forum User

It shows error as SPCD constraint must be constrained with SPC. FEA results are ok but optimization results shows 100% material removal. See attached snaps. I am using DOF 2 to apply enforced displacement in +ve Y direction. Is it correct ?

<?xml version="1.0" encoding="UTF-8"?>

<?xml version="1.0" encoding="UTF-8"?>

tinh

Hi

if you already assigned enforced-disp directly to SPC, then delete SPCD

so you have LOAD (force) on one edge, and SPC(disp) on opposite

please refere to my zzz.fem file

If you run optimization, please organize (move) elems around all SPC and LOAD into 'NonDesign' property, so optimization will not remove material at those area (then your loading condition will not be lost after some iteration)

Altair Forum User

Hey,

Thanks for quick reply.

I  organized elements around all SPC and LOAD into 'NonDesign' components and assigned new property still same error msg.

 

How software identifies design and non design domain? only moving elements to the component of different name will not work. Can you please mention steps to do it ?

 

Also, I am not able to open your attachment in hyper works. Shall I open using Ansys?

 

 

 

 

Rahul Rajan_21763

Altair Forum User said:

Hi all,

 

 

 

 

I am trying to model a combined enforced displacement (with a SPCD) + an applied force. However I could only model it separetly and all the examples I find in the web are about modelling only a enforced displacement or only a force but not both combined. Could anybody help me with this?

 

 

 

 

 

Thanks a lot,

 

 

 

 

 

Regards,

 

 

 

 

 

Mario

 

You cannot have both enforced motion along with external forces acting simultaneously. This physically makes no sense.

What you could do as a workaround is create two subcase.

In the first subcase apply enforced motion and then call this subcase into second one using STATSUB(PRELOAD) command in which you can define external forces.

 

Regards

Rahul R

Altair Forum User

All,

 

One another workaround is to calculate the reaction forces using just enforced displacement and use the same force to combine the force calculated from enforced displacement and actual force.