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Problems with Inventor Nastran (non-linear analysis)

Problems with Inventor Nastran (non-linear analysis)

Problems with Inventor Nastran (non-linear analysis)

(OP)
Hello, everyone,
Thanks in advance for reading and taking care of my problem,

I am currently using Autodesk Inventor Nastran to solve a sequence of press-fits/interference-fits in a plate.
My geometry is a plate with 5 openings (hubs) in which 5 shafts are going to be press-fitted. There is no symmetry, and the openings have different sizes. The assembly of each shaft will produce a stress and displacement field in all other openings, which I must measure and analyze.
What I want to do is: assemble the first shaft and look at the displacement and stress field of the plate. Assemble the second shaft and reanalyze the displacement and stress field of the plate… Do the same procedure until the 5th shaft.

Using the Inventor Nastran I’m struggling to achieve good outcomes, especially for the regions of contact between the shafts and the openings. For an interference-fit in Nastran I must use a non-linear analysis and the results of the contact regions have significant perturbations that invalidate the stress field in this zone. Since interference-fit does not give me a good solution, I have tried to use a shell in the place of the shaft and apply a described radial displacement to the shell until the position I want. For this case I used a simple “separation contact” (do not allow interference) and even this way I get bad and non-physically possible results for the contact zone (with a smaller amplitude right now, but evenly relatively high). I tried using hydrostatic pressure to the shell, however, it is not realistic due to the displacement field of the plate (not uniform around the openings), so it turns out the described displacement is the best solution in my point of view (but please let me know yours).
The problem is that when I constrain a described displacement (forced movement) in Inventor Nastran I must block the same direction of the displacement I want to impose. So, in my case, I must block the radial displacement of the shell to input an actual displacement of its nodes. To impose sequential loads (1 and 2, for example) in Inventor Nastran non-linear analysis I must apply one load in one “subcase”, and both loads in the second “subcase”. This means that to get the result of the assembly of 2 shafts, I must press-fit one shaft in subcase1 and both in subcase2.
This method turns out into a problem for the 2nd, 3rd, 4th and 5th shaft assemblies in which I want to measure the actual displacement and final stress field in all the openings especially in those that already have a shaft assembled. Due to the method, for example, when I press-fit the 3rd shaft, the 1st and the 2nd shafts (shells) have the global position restricted by the constraints I must apply to apply the actual displacement and keep the load throughout the subcases for a sequential load.

In your experience/know-how have faced a close position/similar problem?
Any idea to help me out? Any other way you would use to model this problem?
I am open-minded to different solutions. If you know/use an alternative FEM software (Abaqus, ANSYS, …) that would help me to model my problem and would work fine, please let me know.

RE: Problems with Inventor Nastran (non-linear analysis)

(OP)
Actually, yes.
I posted the same problem many time and in different ways in Nastran Forum, but got no valid answer until today (started it almost 2 months ago).
I thought this forum would be here to, among other topics, help non-experienced/experienced engineers and students (as my case) to solve their daily difficulties regarding MEF problems. Unfortunately, by your tonus, it may not be the case.
As I said in the post, I've tried different ways to model my problem (not restricted to the ones I mentioned) and I still didn't get the results I expect. Therefore, the post is actually for someone that could help me, maybe giving me ideas, with another way to model it up or recommend another FEM software that could easily give good results for my problem.

Thanks anyway,
Best regards,

RE: Problems with Inventor Nastran (non-linear analysis)

(OP)
Actually, it isn't a problem from a school project neither a study object.
This is a problem I'm facing in my internship.
Anyways, I got your position,
Thanks,

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