topic Ynt: load a line in a block for structural analysis in Fusion Design, Validate & Document Forum

load a line in a block for structural analysis

rprovideo — Fri, 03 Nov 2023 17:23:31 GMT

Hi
I have a design I want to test. Its an aluminium block with several holes that are used to divert lines (ropes). I have some questions regarding the analysis in Fusion. Please excuse me if these are beginner questions, i am a beginner in this area. Tried to watch a few tutorials, but they only cover their own designs.

This is what I have. Eventually, I want all the holes have ropes thru it, but I started with a single one.

1, I would use a dyneema rope, they can take up to 12 tons. I loaded this with 20kN, so 2 tons. Since there is no dyneema in the library, I used stainless steel, and it failed (stretched). Now I am using titanium, but it still streches a bit. Not a big deal, but is there something wrong with my model? I am not interested in the rope streching, ideally, i would set this material to infinite or something.

2, I fixed one end of the rope, and added the load on the other end. Also added the screws holding the block down. But if I dont add any more constrains, the rope just comes out of the hole:

now I can fix the middle part of the rope, maybe only on the x direction, and then it would stay. But part of my study is to find if the rope stretches the hole open (if thats the right word) and how much. If I fix the contacting part on the rope, that may never happen. Actually, since the rope is a bit smaller than the hole, if I fix it, it does not touch the side of the hole at all, and (I suppose) no forces will be calculated on my actual item.

3, Would it be better to have the force act on the actual inside wall? Like this

But this is not really accurate, most of the 2-ton load is on the rope (and whats on the other end), the block is actually taking the side load from the angle the rope is diverted. This is much bigger than the actual load (this is me tying the rope in the hole and pulling 2 tons, that will never happen, this is a diverter.

Re: load a line in a block for structural analysis

John_Holtz — Fri, 03 Nov 2023 21:19:25 GMT

Hi @rprovideo . Welcome to Fusion simulation.

You wrote "1. but it still stretches a bit".

How much is "a bit"? The purpose of a simulation is to apply load and calculate how much things deflect. Whether they deflect 100 mm or 0.000001 mm doesn't matter (to the analysis; it only matters to you). There is always going to be displacement. I suggest you accept that. 🙂

Also, the deformed shape is exaggerated by some magnification factor. In the typical linear static analysis, the displacements are small. If the deformed shape was not magnified, you would not see any movement.

You wrote "2. But if I don't add any more constrains, the rope just comes out of the hole".

The answer to this question is you need to define contact between the outside of the rope and inside of the hole.

You wrote "3. Would it be better to have the force act on the actual inside wall?"

Yes. Using forces will run 10 times faster than using contact. (Maybe 100 times faster.) The magnitude of the forces should be known because you can calculate (or assume) the angle of the rope. Besides, I doubt that you will be able to get good results trying to duplicate the material properties of rope in the simulation. Fusion does not have the mathematics to simulate something like rope (weak in bending and compression, strong in tension).

Furthermore, static stress is only valid for small displacements. Even if you modeled the ropes, even if they bent a large angle, the results would not be correct. To get correct results with a model of rope, contact, and bending them, you would need to run a nonlinear analysis. That will run 100 times longer than the linear analysis. Unless it is absolutely necessary, it is not worth the effort.

I hope this helps. At the very least, give option 3 a try since it is the easiest and fastest. If it gives what you need, then your are done. If it only gives your x% of what you need to know, then you move on to the more complex analysis.

John

Ynt: load a line in a block for structural analysis

mufuo — Sat, 04 Nov 2023 07:20:20 GMT

If you know the physical and thermal properties of the material, you can add it to the material library and get a more realistic analysis.
You must create a sliding contact between the rope and the hole. You can add it manually from the Contact section. In addition, the formation of the image in this way may be due to the fact that the result section is not actually displayed.
If you know the reaction force arising from the rope, it is possible to apply it directly to the surface, so you can perform the analysis with fewer elements. If you separate the surface that the rope will touch with the split face command, you will get a more realistic result.

Ynt: load a line in a block for structural analysis

rprovideo — Thu, 09 Nov 2023 10:40:56 GMT

Thank you. It seems, I am not skilled enough in this simulation thing to have it working properly.

I tried to do what you said, and apply the force directly to the hole. I must be screwing something up. It worked once - to my suprise, 5 tons ripped the unit off the screws. Then I realized I left the screws as aluminium. So I changed the material to stainless steel. And now I cannot run the situation.

I have the bolts, the load, and did an Automatic Contacts. When I click on manage, I found it did no contacts, so I tried adding a deck to screw to, and fixed it.

However, in both cases, I end up with an error saying: Error: Incomplete setup: Missing structural loads in load case
Warning: Warning: Some components/bodies in the Model have interferences
Click here to switch to 'Simplify Environment' and open 'Interferences'.
Warning: Warning: Model contains 1 fully unconstrained group(s) in load case "Load Case1".

Also, when adding the deck, the error did not go away, but resulted in this:

Warning: Warning: "Bolt Connector1" may be in conflict with "[S] Bonded1 [Simulation Model 1:1||deck:1]".

I cannot solve the simulation anymore, and I do not know why. I attached the model. I'd be grateful is somebody would point me in the right direction.

EDIT: I readded the force, and the solver ran, but didnt resulted in a result, but an error message:
Causes: Your model is missing a constraint or a contact, causing it to be statically unstable.
(I added the full log file)

Thanks
Balazs

Re: load a line in a block for structural analysis

TheCADWhisperer — Thu, 09 Nov 2023 10:53:35 GMT

@rprovideo

Do you want to learn how to do this correctly step-by-step?

If your answer is Yes, we can get started.

Re: load a line in a block for structural analysis

rprovideo — Thu, 09 Nov 2023 10:56:12 GMT

sure, I love learning. I am watching YT tutorials.

Re: load a line in a block for structural analysis

TheCADWhisperer — Thu, 09 Nov 2023 11:05:08 GMT

@rprovideo

OK, let's get started.

Let's not build a house of cards on a foundation of quicksand.

The purpose of FEA analysis is to be able to make logical edits based on the analysis and get predictable behavior.

Therefore let's build a robust and predictable foundation...

Your Sketch1 is not fully defined - just hanging in space. Blue lines and white dots should keep you awake at night. (Actual color of unconstrained geometry depends on your preferred color scheme setting.)

Step 1. Start a new file and then a New Sketch. Sketch the rectangle shown slightly above the Origin as shown.

Re: load a line in a block for structural analysis

TheCADWhisperer — Thu, 09 Nov 2023 11:08:36 GMT

@rprovideo

Now add a Midpoint constraint between the Origin and the midpoint of the bottom horizontal line of the rectangle.

What do you note about the color of this rectangle after adding the constraint?

Re: load a line in a block for structural analysis

rprovideo — Thu, 09 Nov 2023 11:08:41 GMT

copy that

Re: load a line in a block for structural analysis

rprovideo — Thu, 09 Nov 2023 11:10:44 GMT

yeah, it turned white.

so apart from constraining the dimensions, it has to be constrained towards the origin (or something else)?

Re: load a line in a block for structural analysis

TheCADWhisperer — Thu, 09 Nov 2023 11:11:30 GMT

@rprovideo

Now add a vertical Construction line at the origin and a circle as shown below...

Re: load a line in a block for structural analysis

rprovideo — Thu, 09 Nov 2023 11:12:41 GMT

done

Re: load a line in a block for structural analysis

TheCADWhisperer — Thu, 09 Nov 2023 11:14:57 GMT

@rprovideo wrote:

so apart from constraining the dimensions, it has to be constrained towards the origin (or something else)?

Yes, it makes sense to choose a logical datum against which all changes are made.

The most obvious choice for a logical datum is the Origin center point.

As you progress in learning Fusion there are often significant benefits to making use of obvious symmetry about the origin whenever possible and practical.

Re: load a line in a block for structural analysis

TheCADWhisperer — Thu, 09 Nov 2023 11:19:21 GMT

@rprovideo

Now add a Horizontal construction line floating in space as shown below...

Now add a Coincident Constraint by selecting the vertical line first and then Shift Select the midpoint of the horizontal line.

Re: load a line in a block for structural analysis

rprovideo — Thu, 09 Nov 2023 11:22:16 GMT

I got this
I never used the shift select thing.. I usually just select constraint and click.

Re: load a line in a block for structural analysis

TheCADWhisperer — Thu, 09 Nov 2023 11:22:46 GMT

@rprovideo

Add the circle shown and dimension the height from our single datum as shown.

Add an Equal (=) constraint between the two circles. Note that a diameter dimension is not needed - we have already defined the diameter with the first circle.

Re: load a line in a block for structural analysis

TheCADWhisperer — Thu, 09 Nov 2023 11:26:31 GMT

~~I don't think you "got this".~~

~~From your image it appears that you constrained the midpoint of the vertical line to the midpoint of the horizontal line.~~ That is not the Design Intent.

OK, it isn't constrained so maybe it just looked that way.

Carry on with the instructions.

Re: load a line in a block for structural analysis

rprovideo — Thu, 09 Nov 2023 11:28:32 GMT

No, but to be sure, I went back and tried it several times. No matter where I click on the horizontal line, the result is the same.

(view in My Videos)

Re: load a line in a block for structural analysis

TheCADWhisperer — Thu, 09 Nov 2023 11:30:22 GMT

@rprovideo

Extrude the geometry Symmetric a distance of 24mm as shown...

Note the use of Symmetry.

Re: load a line in a block for structural analysis

TheCADWhisperer — Thu, 09 Nov 2023 11:31:54 GMT

@rprovideo wrote:
No, but to be sure

You are OK, carry on with the steps.