Optistruct Optimization : How to setup an optimization on material ID of components?

Veronique Bouvette

I am used to setup parametered optimization in Hyperstudy. I mostly do it to choose between a set of materials defined in the model. For exemple, I have an assembly of 10 parts and for 3 of the parts, I run simulations changing the material combination (changing material ID). I can then compare how the different materials distribute the pressure and choose the best combinason out of it. However, I want to do the excat same thing in Hypermesh using Optistruct. My final goal is to automate the optimization and I am really more confortable doing so in Hypermesh using TCL. I did not find an Optistruct tutorial that was helpful for what I want to do. My materials are already defined. I just want to set the material ID of some parts as a parameter. 

 

I have trouble setting material ID of the part as variable.  How do I do that?

 

Gildas_GUILLY

Hello Veronique,
In OptiStruct, and in case of a size optimization, you cannot define directly a variable linked to the material ID of a property as you do in HyperStudy.

To have variable changing material characteristics, you need to first define a discrete variable that will represent your material ID, then several relationships linking this variable to each one of the material data (Young modulus, density...) that you want to change from a single material entity (you can use polynomial functions for example for relationships).

However you must be aware that this is not a bulletproof process: what works with HyperStudy (that have good exploratory optimization method) might not work with a gradient-based optimization (Used by OptiStruct).
One thing for example is that you must "call" your different materials in an order that will make sense in terms of sensitivity (by Young modulus ascending order for example).

Depending on what you are trying to do, some other methods might be better suited.
For example the multi-material topology optimization can be used to perform an optimization where OptiStruct will determine what material to be used locally from a list of available materials.

Gildas