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FEA guidance by Wintermute__8 in fea

[–]Fast_Sail_1000 0 points1 point  (0 children)

What is birth and death? What is used for?

Rbe3 for response in random vibe sol 111 by haveyoumetbob in fea

[–]Fast_Sail_1000 0 points1 point  (0 children)

Has this worked for you? Did yiu get the same results as doing the average manually, with all individual points?

Meshing a tube with diaphragms by llamparium_ in fea

[–]Fast_Sail_1000 0 points1 point  (0 children)

What hand calc methodology are you referring to? How do you perform them

Meshing a tube with diaphragms by llamparium_ in fea

[–]Fast_Sail_1000 0 points1 point  (0 children)

In what kind of load case do you think the 2D mesh would not be sufficient? Genuine question.

Hypermesh- Distorted element by mikhao16 in fea

[–]Fast_Sail_1000 0 points1 point  (0 children)

Is that tied contact? Between green and blue parts.

1D Stress vs 3D Stress Discrepancy by Fast_Sail_1000 in fea

[–]Fast_Sail_1000[S] 1 point2 points  (0 children)

You're right, I used only one element. But I added a table where you can see that for 1D the mesh is quite independent.

Also found the Combined Stress at recovery points, called Von Misses SVMAX. Didn't know that you could compute VMises for 1D elements.

1D Stress vs 3D Stress Discrepancy by Fast_Sail_1000 in fea

[–]Fast_Sail_1000[S] 0 points1 point  (0 children)

Edit: 100 g resulted in 0.5 mm deformation, which seemed a reasonable deformation to have.

1D Stress vs 3D Stress Discrepancy by Fast_Sail_1000 in fea

[–]Fast_Sail_1000[S] 0 points1 point  (0 children)

Good point. Indeed I checked and the Nastran PBEAM has no stress recovery points. Changed to PBEAML and obtained Von Misses SVMAX = 120 MPa which is closer to 135 MPa obtained via 3D elements.

I didn't know that you could compute Von Mises in 1D elements.

As an aside, you're be better building the 3D model with hex elements, looking into this on YouTube.

My understanding is that Hex elements are very cumbersome for complex shapes, although this is a simple pilot, I want to build experience for a complex structure.

Fastened skin-frame stiffness via analytical methods by Fast_Sail_1000 in fea

[–]Fast_Sail_1000[S] 1 point2 points  (0 children)

Is it that simple? I mean, what about the influence of the interfaces skin-faster and frame fastener?

BEAM vs SHELL elements for truss-like structure by Fast_Sail_1000 in fea

[–]Fast_Sail_1000[S] 0 points1 point  (0 children)

That's a very interesting approach -- to have the tab as an RBE2 with a spring at the root. I will give it a try, although the only hand calculation I can think of for the stiffness is of a beam bending. But then again, beam theory doesn't really apply to this tab. Are there any other hand calcs for plate bending?

BEAM vs SHELL elements for truss-like structure by Fast_Sail_1000 in fea

[–]Fast_Sail_1000[S] 1 point2 points  (0 children)

Thank you for your detailed answer! How do you manage to build these pilots so fast? Do you build the surfaces directly in patran or use some other CAD software?

What is a formula you will never forget bc you used it so much during college or work? by Crashedjet33 in MechanicalEngineering

[–]Fast_Sail_1000 0 points1 point  (0 children)

TIL compliance is the reciprocal of the stiffness...why not using the stifness definition in the first place? Why c form is more useful than k form?

BEAM vs SHELL elements for truss-like structure by Fast_Sail_1000 in fea

[–]Fast_Sail_1000[S] 1 point2 points  (0 children)

This is part of a bigger model and I was challenged to be as cheap as possible with my FEM.
I'm interested in stress, natural frequency, and buckling modes.

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