Inventor Stress Analysis help

[Anonymous]

Good day!

I am using Inventor 2011 Professional. I have a cylindrical part that gets crimped by a hex die in a hand tool. The problem I am solving is that the cylindrical part is buckling and not conforming to the hex shape of the die. I have a CAD model of the part that gets crimped. I modeled up a die and created an assembly with the part and the two halves of the die. What I want to do is use the Stress Analysis function of inventor to apply a force to the die. I need to crush / crimp the part with the die to determine the deformation and stress at key locations on the part.

I know the obvious solution is to just make the part thicker. However, I have been tasked with running FEA on this setup to determine exact deformations and stresses.

I setup my assembly in the stress analysis workbench. I applied my materials, applied my constraints to only allow motion in the direction the dies travel and only for the dies, applied two forces on the two halves of the die, generated a mesh and ran the simulation. The problem is that I keep getting numbers that do not make sense. The material of the part is Brass Alloy. The material of the dies is steel. The yield stress of the brass I am using is approx 28 ksi with an ultimate tensile stress of about 71.1 ksi. I ran the simulation itteravely to find the value of the force until the cylinder fully deformed to the point that the dies fully close and touch. The value of the force required to close the dies immediately stands out as way to high. I know they currently make these with hand crimp tools, but the value Inventor tells me is 70,000 lbs of force to close the dies. Also, the von Mises stress values are way off the scale. My yield stress for brass is about 28 ksi, but the stress Inventor gives me is like 27,500 ksi.

Please see attached images. Note: I was unable to achieve the proper deformation with a hex die model, so I changed to a square die model instead. The principals are similar.

Is there something wrong with my setup? I think I am definitely close. I think the problem might be that either my setup is not quite correct, or that I am asking Inventor to do something it may not be able too ... any help would be greatly appreciated.

I can supply the models or more images to help out further.

[JDMather · Accepted solution]

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@Anonymous wrote:

Good day!

I can supply the models or more images to help out further.

...or that I am asking Inventor to do something it may not be able to do...

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Supply the models.

Be aware that Inventor FEA is only valid in the elastic range and for relatively small deformations.

Sounds like you are trying to test into the plastic range (permanent deformation).

[Anonymous]

I am unable to upload the part files or the assembly files. They are just over the file size limit to attach in the post. I can send them by email?

I am trying to test in the plastic deformation range. The part is crimped and deforms plasticly to the shape of the die. There is a fair amount of deformation the part undergoes (from cylinder to hex cyinder).

So sounds like Inventor is unable to calculate my problem because it is unable to calculate perminant deformation (which is my case).

I can still email you the files if you want, but sounds like I am in a circumstance that is outside of Inventor's capabilities.

Thank you again.

[JDMather]

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@Anonymous wrote:

I am unable to upload the part files or the assembly files. They are just over the file size limit to attach in the post.Thank you again.

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Open the part file.
Drag the red End of Part marker at the bottom of the feature tree to the top of the browser hiding all features.

Save the file with the EOP in this rolled up state.

Now how large is the file?

Right click on the file name in Windows Explorer and select Send to Compressed (zipped) Folder.
Now how large is the resutling *.zip file?