Fabricio wondered why his fastener model that consisted of a Head, Shaft and Nut had such a different value of peak stress depending on whether it was a 3-body multibody part or it was Boolean United into a single body. Below is the difference he was seeing.
The first image is the 3-body result. Note the peak is 821 MPa.
The second image is the 1-body part. Note the peak is 627 MPa.
Most of the difference is due to the setting Average Across Bodies set to No, which is the default.
If the Average Across Bodies is set to Yes, then there is little difference between the mulitbody part and the single body part. Note the peak goes down to 615 MPa.
It is understood that this model includes a stress singularity due to the sharp interior corner at the shaft, so comparing peak stress is somewhat pointless since any reduction in element size around the corner is going to result in a higher stress. The point of this post is to show that stress results on multibody parts should have Average Across Bodies set to Yes if they are all the same material.
Fabricio also asked how to get the full element display on the section view. It is by clicking the diamond shaped icon on the Section window.
Now here are the three section view:
It seems the elements are actually a little better quality in the 1-body mesh than the 3-body mesh above. I expect with a little work, the 3-body mesh could be made to look like the 1-body mesh.
Attached is an 18.2 archive.