How to handle components that dont play any role in structural behaviour?

[ptsal]

Hey guys,

I have the structural part of my model already finished, however that is not enough because I need to include all the other components that will influence the dynamics of the whole model. I want to have the influence, for example, of the weight and inertia of my motor, however I dont want to have a solid instance cause my model is already huge and I'm trying to reduced the number of DOF as much as possible.
So I wonder what the alternative is. I am afraid that with discrete rigid elements the whole structure becomes stiffer than it really is.

So my main question resumes to this: I want to include the inertias and weights of the components and I dont know how should I connect them to the main structure, without influencing the strcuture stiffness.
(I hope I was clear enough)

I'm little confused with this, so If someone could give me some ideas I'd appreciate.

Thanks in advance,
PTsal

 

[burningDiesel]

Add point mass & inertia, and couple them with your existing parts.

interaction->special->inertia

 

[ptsal]

I already thought of doing it that way, however I don't think that is the right way to do it.

For example, if I have four support points for the point mass & inertia and if I couple the point to those 4 points, it is as if I have a rigid connection between the four support points, and I dont want that.

Do you know any alternative to that?

 

[burningDiesel]

Use connectors to connect the mass, and give them an elastic behavior (with possible damping). Alternatively, you could use substructuring to represent your engine by one 'mega-element', see e.g. 3.2.2 Substructure analysis of a pick-up truck model. I've only used it in static sims, but manual says you can use in dynamic also.