Static analysis of a structure with a spring

kunitsavova · ‎01-08-2021

Dear friends,

I have to turn to the respected community and professionals for help.
At first glance, a completely ordinary task opened up a huge number of questions and controversial points. I could not find any hint in the official documentation and resources for the program. Having spent a huge amount of time looking for such examples, I decided to write to you all the same.

So. The crux of the matter is in the static analysis of a small structure.
Two metal triangular elements are interconnected by a single axis in which rotation takes place. The opposite ends of each element are located on the axes where rotation also occurs. The axes themselves are rigidly fixed in 2 planes and have a degree of freedom along Z. A spring is installed on top between the two triangles. The essence of this analysis is to understand how the spring and each structural element behave when a force is applied vertically to one of the triangles. Contacts in this analysis are set as separated for all bodies except for attaching the spring to the left triangle.
Questions:
1. DOF. Is static analysis possible if only 2 axes are not fully fixed in the structure, and the rest of the bodies have separate contacts in order to rotate relative to each other.

2. Spring. The documentation for the program says that one of the conditions of static analysis is when the deformations and displacements of bodies are insignificant or very small. In this regard, do the deformations of a compressible metal spring fit into the criterion of static analysis or are they already referred to as nonlinear analysis? In Solidworks, by the way, in static analysis the spring is included in the type of boundary conditions. When applying nonlinear analysis (with nonlinear materials) to the spring separately and to the entire structure as a whole, Fusion 360 gives an error and refuses to solve.

3. Results. The animation of the static analysis results looks unlikely. When the actual deformations are turned on, the bodies enter each other.

If anyone has done simulations of structures with springs, as well as similar conditions (DOF, contacts), please share your thoughts.

I'll be very grateful to you.

Thank you in advance.

Sincerely.

Vova

TheCADWhisperer · ‎01-09-2021

Can you File>Export your *.f3d file to your local drive and then Attach it here to a Reply?

kunitsavova · ‎01-09-2021

Thank you very much for your reply.

This file is here.
Thank you in advance.
Vova

TheCADWhisperer · ‎01-09-2021

If this were my design -

I would fully define each and every sketch.

I would not have any duplicated dimensions.

I would model appropriate clearances between moving components.

I would model as separate components.

I would do the analysis in Autodesk Inventor Professional>Dynamic Simulation.

kunitsavova · ‎01-10-2021

Thank you very much for your answer.
May I ask if I understood correctly:

1. Is the setting of clearances between moving components and changes of the same size a desirable or necessary condition in preparation for the EFA? I believe that if the bodies do not have mutual penetration even if their dimensions are the same, for example, the diameter of the axis is equal to the diameter of the hole, the definition of separate contacts between the bodies automatically sets the correct relationship. Or?2. Dynamic Simulation in Autodesk Investor Professional makes it possible to simulate assembly kinematics in the real world. With the dynamic I build a functional mechanism. But my main task is to test the strength of the mechanism, to find out the zones with high stress, to determine the Safety Factor. It seems to me that FEA analysis is more suitable for these purposes. If yes, then we return to the question: what FEA analysis is suitable for such a construction where there is a spring?
3. Is such an analysis possible in the Fusion 360 environment or, despite the fact that Fusion uses the same Nastran solver, is it better to solve such assemblies in Inventor?

Thank you in advance.

TheCADWhisperer · ‎01-10-2021

@kunitsavova wrote:

1. Is the setting of clearances between moving components and changes of the same size a desirable or necessary condition in preparation for the EFA?

2. But my main task is to test the strength of the mechanism, to find out the zones with high stress, analysis is suitable for such a construction where there is a spring?

3. Is such an analysis possible in the Fusion 360 environment

1. No, but I design for the real world. (First I would fully define my sketches - but that isn't necessary for FEA either - it just makes editing based on analysis results easier.) (And in my experience - those who do not fully define their geometry have other problems using the analysis results. Usually their geometry is flawed.)

2. I would use a Spring Force rather than a modeled spring. I would be interested in motion loads analysis that includes twisting forces. (First I would fully define my sketches.)

3. I am sure it is possible in Fusion, but I am lazy, I expect that I would be interested in multiple time-step positions and would not want to have to set these up individually. (First I would fully define my sketches as I am expecting that I would make changes to the design based on the analysis results.)

4. You probably should have posted this >>over here<<. But, given that the sketches are not constrained - I have lost interest in this analysis. Hopefully someone over there will continue the discussion.

kunitsavova · ‎01-10-2021

Dear friend,

Thank you so much for such a detailed answer.
I ask you to excuse me for sending you a model where the drawing is not fully defined. I was in a bit of a hurry, especially since this model was made for clarity. I thank you for your advice and will try to take it into account. Especially your advice about the sketch as it is probably the most important.

In fact, I hoped to use this topic to raise the issue of simulating such structures with springs in Fusion. There really isn't enough material on this topic. If I could find a description of such solutions in the documentation for the program or in the official tutorials, I probably would not ask anyone. Forum mentors have already reproached me for wanting a ready-made answer to my question. But, excuse me, what is the forum for then? Where else can you go?

I have no doubt that this can be done in Inventor. If I wrote about this on the Inventor forum, then probably my wording of the question would look a little different. The fact is that not everyone who uses Fusion has the opportunity to work in Inventor.

Thank you very much.