volumefrac bounds in dconstraint of topology

Altair Forum User

hi,

 

I would like to know ,

 

1) what would be happening when we define volume frac bounds ( as dconstraint ) in topology problem. I mean in one case I would define lower bound 0.4 & in other case upper bound 0.4. 

 

2) how different my solution would be , based on upper / lower bound constrain for volume frac ? 

 

3) which one is better constraining option for a given topology problem , lower bound / upper bound of volume frac ?

 

 

Your inputs are highly appreciated

 

 

Thanks,

 

 

Merula_20758

Hi,

 

volumefrac is the fraction (optimized volume/original volume). So to answer your questions keep this in mind

 

1) Lower bound set to 0,4: the solver takes minimum 40% of the original volume to optimize. If you do not constraint an upper bound as well it might go to 100% if it is structurally necessary

 

Upper Bound set to 0,4: The solver is allowed to take maximum 40% or less material for the optimized design.

 

 

2) Case 1 (lower bound constraint): More ribs, even the whole designspace might be filled with material as the solver is not forced to do otherwise in order to fulfill the constraints.

Case 2 (upper bound constraint): In dependancy of the value, more or less material is placed (e.g. vf upper = 0,1 means less material than vf upper = 0,4)

 

3) With my simulations I have always constrained the upper value. lower value can be constrained but never without the upper value constraint.

 

All the things mentioned above assumed that you want to minimize your compliance at a given vf dconstraint.

 

Regards,

 

Merula

Altair Forum User

Hi,

 

For example, If I give an upper bound of 0.3 this means 70% of the material should be retained in the design space.

 

Usually using Upper bound is recommended.

Merula_20758

Edited

Altair Forum User

Merula,

 

you are right, I was confused while writing.

 

I have edited the statement.

Altair Forum User

Altair Forum User said:

Hi,

 

volumefrac is the fraction (optimized volume/original volume). So to answer your questions keep this in mind

 

1) Lower bound set to 0,4: the solver takes minimum 40% of the original volume to optimize. If you do not constraint an upper bound as well it might go to 100% if it is structurally necessary

 

Upper Bound set to 0,4: The solver is allowed to take maximum 40% or less material for the optimized design.

 

 

2) Case 1 (lower bound constraint): More ribs, even the whole designspace might be filled with material as the solver is not forced to do otherwise in order to fulfill the constraints.

Case 2 (upper bound constraint): In dependancy of the value, more or less material is placed (e.g. vf upper = 0,1 means less material than vf upper = 0,4)

 

3) With my simulations I have always constrained the upper value. lower value can be constrained but never without the upper value constraint.

 

All the things mentioned above assumed that you want to minimize your compliance at a given vf dconstraint.

 

Regards,

 

Merula

thanks....

Altair Forum User

Altair Forum User said:

Upper Bound set to 0,4: The solver is allowed to take maximum 40% or less material for the optimized design.

Hi Merula,

 

what I understand from above quoted statement is 60% of the material is constantly maintained throughout optimization and is not optimized, remaining 40% of the design space material is only taken for optimization. Is this correct ? 

 

Thanks in advance.