Autodesk Inventor

[#1]

Hi all,

Wondering if someone could help me. The problem is simply reconciling stress analysis results with hand calculations and I suspect I'm simply setting up constraints incorrectly or something.

A simple problem of an M6 bolt in single shear as in the image below. I am using the forumla in image to calculate the shear stress. The diameter (being an M6 bolt) is 6mm and hence radius is 3mm with a shear force of 1000 N being used. Using the forumla in the image below and the figures above, I calculate the shear stress in the bolt to be 35.4 MN/m^2 or 35.4 MPa if you prefer.

My problem is that when I simulate this problem in Inventor 2013 stress analysis the results (for any kind of stress analysis; Von Mises, 1st and 3rd principal, all the planes etc...) are way way off what the hand calculation is, ranging from 160 MPa to around 800 MPa.

Could somebody with the time to do so possibly talk me/post images of how to set this example up in Inventor correctly so that you get the same (or near enough) result.

Many thanks,

Sam

[#2]

Attach the ipt file here.

Your formula gives the area of a circle where the image shows the force across the face area of two cylindrical faces.

[#3]

Any progress on this?

Force over area of a circle or area of a cylindrical face?

[#4]

Hi JD,

Still no luck really. I appreciate what you're saying in that in my forumla the force is acting over the cross section of a circle and doesn't take into account the thickness. I've used a different forumla: Shear stress = F/Dia.*(t1+t2) but still similarly disproportinate results. Besides all the text books I've used state the forumla I originally posted.

Here's a link to the IPT file if you wanted to have a look at how I've set it up (which may well be incorrect). It was slightly too big to attach directly.

http://dl.dropbox.com/u/35359353/Shear%20stress%20in%20bolt.ipt

Regards,

Sam

[#5]

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samstreet101 wrote:

Here's a link to the IPT file ...

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ipt files can be attached directly here.  I don't go to 3rd party sites.

[#6]

It wouldn't let me attach it directly as it said the file size was too big. It's just a dropbox link, if you prefer I could email it to you. Or is there a way to shrink the file size?

[#7]

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samstreet101 wrote:

Or is there a way to shrink the file size?

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Find the red End of Part marker at the bottom of the browser.
Drag the red EOP to the top of the feature tree hiding all features.
Now save the part with the EOP in this rolled up state, the file should be much smaller.

If it is still too large (over 1.5M) then right click on the filename in Windows Explorer and select Send to Compressed (zipped) Folder.  Attach the resulting *.zip file here.

I am a bit curious how geometry as simple as that which you depict could be so large a file size, so later when I get to my "safe" test machine where I can download anything I will try your dropbox link.

[#8]

Did what you said, also deleted the simulation from it and put it in a .zip folder.

[#9]

I think something is wrong with this file but I haven't figured out what, yet.  The file size is much larger than I would expect.

[#10]

The shear stress (4F/PI*D^2) is the formula for AVERAGE Shear stress on the cross section.  Your math is correct for this single shear problem (35 MPa).

The stress JD is talking about is the Nominal BEARING stress which equals P/A.  Where A= D*t.  In your case, D=6 and t=3.  So the nominal bearing stress would be 1000/(6*3) or 55.6 MPa.

I tried to setup the stress analysis on my own part also, but I couldnt get Inventor to give me the correct answer.  I suspect it is because FEA is looking at an infinitesimally small point that cause the stress to increase.