writing DRESP3-Card (here: Tresca-Stress)

Altair Forum User

Hello,

 

as suggested in another thread in this Forum, i tried the usage of dresp3-Card.

 

What i want to do:

- let excel calculate the tresca-stress (Input: max principle, min principle, output: stress (=difference between both input variables).

- get the tresca stress back and use it for an 'minmax-' or 'min-objective' in optimisation

 

What i wrote until today:

 

LOADLIB DRESP3  GR01    tresca.xlsx

$solid

DRESP1  1       MAX_PR1 STRESS  PSOLID          SMAP
DRESP1  1       MAX_PR3 STRESS  PSOLID          SMIP

 

DRESP3  20      TRESCA  GR01    MYFUNC  1       2
+       DRESP1  1       2
+       CELLIN  C2      C3 
+       CELOUT  D1

 

I also use a small excel-file, which calculates the difference beween 'cell C2' and 'cell C3' in 'cell D1'.

 

Questions:

- would it work like that ? (I can't test it at the moment)

- What do I get with the DRESP1 / DRESP3 ? When using DRESP1 with 'ELEM' and enter an element-ID, it would give ONE value to the excel-file, which seems to be pretty clear. But when I use PSOLID as the PTYPE, there might be hundrets or thousands of values (here: principal stresses). At that point I do not understand my own programmed code..

 

Maybe someone can help?

I read the Tutorial OS-4095 and also a lot of manual pages.

 

Thanks a lot 

 

Altair Forum User

I got a running Model now, but I didn't use dresp3 but dresp2 with dequation. With dreport I get the right values now in my outputfile.

But i can't use these values for constraints / objectives. Optistruct unfortunately understands, that an equation with two stresses as input always results in a stress, so my resp2 is a stress-response (even though it is a 'formula'-response..). Due to this fact i get error 1800, which tells me to use the stress-constraints in the desvar-panel instead...

 

Any thoughts?

 

What i want to do is to reduce the maximum stress (=objective). That means I only need the greatest stress as ONE response and not as many responses as myy number of elements... Any help on this point?