Inventor 2011: Is it possible to do stress using only force as constrains?

[bli22]

I am working on a project to model a telescope mirror.

The problem now I face is that I want to do a stress analysis to see how it deforms, in the analysis only force can be use as constrain.

It is possible with inventor? and How?

Thanks

[blair]

You will still need to establish some for of constraints, your mirror cell/support structure as well as establish the direction of gravity.

Think of constraints as your mount points. You must still hold/support your mirror. Use a constraint only in the axis of your load/gravity. This will act as a simple support and not a rigid/fixed support if you use all three axis.

If it's a "Cass" mirror, I would use a single axis constraint on the base center opening, if a Newt a single constraint on the bottom outer base ring and try one using a small center ring on the base.

Use different directions for Gravity.

You should get the displacements you are looking for.

I'm working on a lightweight 16" f4.5 Dob in my spare time.

[Dan_Margulius]

Hey ,

what Blair said is correct. it is better to add constrains to mimic real life behaivour of the model.

But if you think you have only forces than you should check rigid body modes in analysis settings.

That tells Inventor you have partial constraints or no constraints at all. For example you want to do a modal analysis on a plane.

So the plane has no constraints then you have to check that box.

[blair]

In the FEA world, think of your part floating in a zero-gravity enviroment. It is not constrained, any force that acts upon the body is free to move the body in the direction of the force.