*** INTERNAL PROGRAMMING ERROR # 8004 *** Data block ix has zero length. * DATAMANAGER ERROR in subroutine "datami".

Viking_d

Hello, 

I am trying to run a free-size optimization on my composite structure.

I have a stress constraint, which I have defined in DCONSTR referencing the Static Stress response. 

My objective is to minimize the Mass_response and also the stress_response at the same time. How do I go about this? I created DOBJREF for both the stress response and the mass response and tried using MINMAX, but it throws an error. What is the right way to do it?

For now, to make things simpler I have just defined the objective function to minimize the mass response while applying stress constraint DCONSTR. I get the following error while trying to run it. 

*** INTERNAL PROGRAMMING ERROR # 8004 ***
Data block ix has zero length.
* DATAMANAGER ERROR in subroutine "datami".

 

Any help on fixing this is appreciated. 

 

Thanks

RobHoglund

Hello,

It's not a feasible formulation to minimize mass and stress at the same time- minimize mass, and stress goes up; minimize stresses; and you'll end up with additional material.  Also, one cannot constrain a response and set it as the objective at the same time.

One way to do this is with minimizing mass, subject to stress constraints; and then understand how much mass could be removed at different levels of desired stress.

If you can share that .fem file we can better understand why that error is occurring.  It's possible it could be related to manufacturing constraints in the optimization.  You can try running the free-size optimization without different ply mfg. constraints and just the stress constraint.

Thanks,

Rob H.