# OptiStruct MPC Constraints and Material Questions

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Posted (edited)

Currently I’m working on my thesis and for this I’m using Hypermesh 2017.

I have a few questions regarding Hypermesh 2017 and I would be really thankful if you could help me:

1. I’m using a model, with 6 sides, which should be constrained with MPC on 3 sides and also be restrained on the other 3 sides. I actually couldn’t find the exact option for the restraints, so I guessed the best option is to use the “Suport1”. So I wanted to ask you, if you would recommend this “Suport1” for restraining the model or is there another option to restrain?

The question here is: what do you want to achieve? To constraing the structure by locking single degrees of freedom to zero displacement, please use the SPC type for constraints.

The MPC type is meant to lock a degree of freedom from one node to another node (e.g. Node 1 should move the same amount in x as Node 2)

The Suport Constraint is meant only for inertia relief analysis - so for cases in which you constrain a structure by defining an opposing force (e.g a plane wing in the air is held by an opposing inertia force).

1. The Force/Pressure which should be applied to the model increases in proportion. So I wanted to ask you, where do I find the option to solve this

Please use the "equation" option in the forces panel to define a force / pressure distribution which is e.g. linearly increasing

1. Which is the best Material Card for ABS (acrylonitrile-butadiene-styrene) in Optistruct? I have the stress-strain-curve and also the values for E, Nu, and Rho?

I can't really answer this, as it depends on your material curve (which I do not know). For a general stress strain curve, please use the MATS1 Material model

MATHE would be the correct material, if your material has a hyperelastic behaviour

1. Is there a Material Card for Visco-Elasticity Material in Optistruct?
2. Is there an option to define MPCs and Restraints in Radioss Block100? Or is this only possible in Optistruct?

You can define constraints also for the RADIOSS Solver by using the RADIOSS User Profile in HyperMesh

Edited by Jan Grasmannsdorf
Typo

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There is no visco elastic material in Optistruct. You can implement User materials for this.

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