Bolt Stress Results

[Anonymous]

Hello,

I have created a simple shear joint to understand the stress calculations in 2 5/8" bolts.  No preload was applied and separation contact was defined.  Why are the stress results so high for the beam elements?  Looking at the beam beam forces the stresses in the fasteners should not be as high as Nastran is saying they are.  

Running the latest version of nastran inventor.

Appreciate any suggestions.

Thanks,
Paul

[Anonymous]

Here is the axial bolt stress check.  Again the beam stress results don't appear correct looking at the beam bolt forces.

[Anonymous]

Here is the compression check also.  Notice the high beam stresses compared to the beam forces.

Thanks,
Paul

[John_Holtz · Accepted solution]

Hi Paul,

Your hand calculations are not considering the bending stress. All of Nastran's outputs include the bending stress. 

See this article on knowledge.autodesk.com: How are beam and bar stresses calculated in Nastran.

[Anonymous]

Hi John,

Simple shear stress check is F/A.  Attached is a snap shot using PTC Creo Simulate of the exact same problem that gets the correct answer per my hand calcs.  This is my basic question:

1. Why do I not see a shear stress result for the nastran fastener like Creo Simulate?

2. Why is the beam Von Mises stress 85,540psi when the shear force is ~5,000Lbs (that is an order of magnitude wrong).

Appreciate any suggestions you have.  I have a structure of 150 of these fasteners and the customer is asking detailed fastener results.

Thanks,
Paul

[Anonymous]

Hi John,

I looked at the Von Mises stress inside of PTC Creo Simulate and you're correct it is including the bending stress also and it is the causing the high Von Mises Stresses.

For this structure of 150 fasteners I guess to provide go no go results I'll just report out the axial force and calculate the resultant shear force from plane #1 and plane #2 ignoring the stresses.

Thanks,
Paul