Sheet metal contact

J82

I have a fairly simple sheet‑metal assembly, and I’d like to analyze how the structure deforms when the parts are joined with pop rivets. Since the connection is made with rivets, the joint can’t be modeled as bonded, because that would prevent the model from showing the actual flexibility of the structure.

Thank you in advance.

Sebastianmaklary

We can't see the geometry in the file because we don't have the STEP files. The geometry isn't included in the .liml file until you've meshed it, so please do so.

J82

Thank you for the notice. Please find the new file attached.

Fatmac

assign the material to the parts then bond them together

Fatmac

if u wish to connect the parts by just the rivets then bond using the surfaces where the rivets connect to - see pics

J82

Thanks. I created the contacts the same way as in the images. That doesn’t represent the actual situation, where the surfaces is not connected along the entire length as it appears there.

Victor

You can use Node-surface coupling with the RBE2 option and applied to the edges of both holes to fix them together rigidly. Pick any node on the hole edge as the reference node.



Or to allow the holes to deform, use two RBE3s with their reference nodes connected by a high-stiffness beam.

Fatmac

I had a look at this using solid pop rivets - i introduced a bit of pretension in the rivets by cooling them. The overall deformations look sensible.

However, a quick look at the stress in the rivets made me a little suspicious of the results -this model suggests the rivets at the ends are under more duress than the ones in the middle- not what I would have guessed -perhaps I have made some incorrect assumptions/setups?

Victor

Those peaks of stress on the rivets might be spurious due to the contacts or the re-entrant corners under the heads.

One on the end has the slave faces extending beyond the master faces. I corrected that and it slightly reduced the stress.

If you look at Stress YY, it shows almost equal positive and negative stress within the same rivet, so you'd have to find an average to compare the overall tension in each rivet. Perhaps for a quick result, take the stress at a node in the center. On the row in tension , that shows 1.4 MPa at the end and 3.6 MPa in the middle on the symmetry plane, so the same order you'd expect.