Multiple load collectors into one load step

Tom Southall

I'm running a topology optimisation of a part for a university project. I want to create a solution that is optimised for two loading conditions.
I think I can achieve this by using two different Load Steps for the different load cases (please let me know if this isn't the case).

In each load case two of the forces are the same however the third force which is a side force is just acting in the opposite direction with the same magnitude. I was hoping that I would be able to use one load collector for the two forces that are used in both cases and then create two more Load Collectors for the different side forces. Then in each Load Step I would add to Load Collectors: the first that is common and then the relevant side load. However I don't think I can add two Load Collectors to the same Load Step.

Please let me know if it is possible to add two Load Collectors.

If not will I need to create two separate Load Collectors, with three forces in each one for that relevant load case? This would just seem odd to have to create the same force twice for different load cases despite it being the same in both.

loistf

Tom Southall said:

Will I still need two different load steps and two objectives to make a solution that is optimised for both cases?

Hi! When optimizing, you should think in term of responses primarily. You optimize for responses (that are dependent or not) on load steps, not on loadsteps themselves.

Also, you should know that you cannot simple link more than one response to an objective, you need to combine they (typically weight-average or minmax are the strategies).

Hopefully this helps.

That said, my guess is that you need two load steps (just a guess, we don't know much yet about the responses that matter to you) and either:

-one objective with a weighted average of the responses for each subcase

-one objective and several contraints, each referring to the step-dependent responses for each subcase.

Tom Southall

I've just tried creating a second load case and I realise that I will need to create another objective for this load case. Once I've created both should I get a result that is optimised for both?
If not how would I achieve that?

Ben Buchanan

You can use a loadadd card to add different load collectors and then just reference that loadadd card in the load step.
https://help.altair.com/hwsolvers/os/topics/solvers/os/loadadd_bulk_r.htm

Tom Southall

Ben Buchanan said:

You can use a loadadd card to add different load collectors and then just reference that loadadd card in the load step.
https://help.altair.com/hwsolvers/os/topics/solvers/os/loadadd_bulk_r.htm

Will I still need two different load steps and two objectives to make a solution that is optimised for both cases?

loistf

Tom Southall said:

Will I still need two different load steps and two objectives to make a solution that is optimised for both cases?

Hi! When optimizing, you should think in term of responses primarily. You optimize for responses (that are dependent or not) on load steps, not on loadsteps themselves.

Also, you should know that you cannot simple link more than one response to an objective, you need to combine they (typically weight-average or minmax are the strategies).

Hopefully this helps.

That said, my guess is that you need two load steps (just a guess, we don't know much yet about the responses that matter to you) and either:

-one objective with a weighted average of the responses for each subcase

-one objective and several contraints, each referring to the step-dependent responses for each subcase.