ERROR # 1812 Optistruct Topography Optimization

Debarshi

Hi.

I want to perform a topography optimization analysis for this part. Yellow is the non-design space and blue is the design space. The big rigid is SPC and small rigid is loaded. I want to have minimum displacement in X in around the middle hole. Everything is shell mesh with 5mm thickness. I am using a higher thickness as it is a solid body in reality.But I am getting this error.

 

Please help me out. Thanks in advance.

*** ERROR # 1812 ***
Multiple responses are assigned to the DESOBJ objective function.
A MINMAX/MAXMIN objective function definition with DOBJREF should
be used instead.
Number of responses = 181

This error occurs in module "dppdrv1".

Adriano Koga_20259

Hi @Debarshi 

 

OptiStruct supports only a single value as objective, which means that your response cannot be composed of many different nodes.

As stated in the .out file, you could change your setup to a MinMax(displacement), instead of minimize displacement.

For this you need to create a 'Objective Reference' first, selecting your displacement response, and giving it negative and positive references. References are scalar values that will be used to "normalize" your displacements. If you use 1.0 as positive reference, it will only take your displicament values for each node, and divide by 1.0, if it is positive.

In the end, after creating this objective reference, you will define your objective as MinMax(objrefDisp).

In this case, OptiStruct will first of all rank all your normalized displacements, picking the maximum of them, and then it will try to minimize this maximum value, thus chasing only 1 value at time, instead of all nodes at the same time.

Adriano Koga_20259

Hi @Debarshi 

 

OptiStruct supports only a single value as objective, which means that your response cannot be composed of many different nodes.

As stated in the .out file, you could change your setup to a MinMax(displacement), instead of minimize displacement.

For this you need to create a 'Objective Reference' first, selecting your displacement response, and giving it negative and positive references. References are scalar values that will be used to "normalize" your displacements. If you use 1.0 as positive reference, it will only take your displicament values for each node, and divide by 1.0, if it is positive.

In the end, after creating this objective reference, you will define your objective as MinMax(objrefDisp).

In this case, OptiStruct will first of all rank all your normalized displacements, picking the maximum of them, and then it will try to minimize this maximum value, thus chasing only 1 value at time, instead of all nodes at the same time.

Debarshi

Adriano Koga_20259 said:

Hi @Debarshi 

 

OptiStruct supports only a single value as objective, which means that your response cannot be composed of many different nodes.

As stated in the .out file, you could change your setup to a MinMax(displacement), instead of minimize displacement.

For this you need to create a 'Objective Reference' first, selecting your displacement response, and giving it negative and positive references. References are scalar values that will be used to "normalize" your displacements. If you use 1.0 as positive reference, it will only take your displicament values for each node, and divide by 1.0, if it is positive.

In the end, after creating this objective reference, you will define your objective as MinMax(objrefDisp).

In this case, OptiStruct will first of all rank all your normalized displacements, picking the maximum of them, and then it will try to minimize this maximum value, thus chasing only 1 value at time, instead of all nodes at the same time.

Thanks. Adriano. That way it works. I have an another question. Does solid mesh work with topography optimization? Because I have seen most of the examples with shell mesh.

Can the design space and non design space both be solid mesh?

Can the design space be shell and non design space be solid mesh?

Thanks.

 

Regards,

Debarshi

Adriano Koga_20259

Debarshi said:

Thanks. Adriano. That way it works. I have an another question. Does solid mesh work with topography optimization? Because I have seen most of the examples with shell mesh.

Can the design space and non design space both be solid mesh?

Can the design space be shell and non design space be solid mesh?

Thanks.

 

Regards,

Debarshi

Yes. Topography is applicable to solid elements.

Take a look at OS example section. (attached example)