fastener loads in FEM from a modelled lap joint

[jedstress]

Hello all,

I created a simple FE model representing a basic lap joint with the two surfaces of equal thickness (represnted by shells) modelled 3mm apart to simulate eccentricity. i have idealised the fasteners as bar elements. however, i cant understand why one end of the bar element(s) is seeing huge bending moments whilst the other is seeing negligible amounts. i experienced the same issue with bush elements too.i was expecting the moments to be more or less equal on both ends, but the results seem to suggest one end is pinned. i have checked the bdf sevral times to ensure both ends are fully built in.
has anyone ever come across such an issue before? am i overlooking something here?please refer to the attached file for details on the results, including bdf and f06.

Thanks in advance

 

[rb1957]

is the 0.18" deflection sensible ? (ie 1/2 the offset between the plies) ... the sensible solution is for the load to deflect to align with the reaction. is the reaction pinned ? (maybe with a rigid body constraint, Mz ?, which should attract zero load).

it's really tricky modelling these small effects ... take a symmetric (double shear) problem.

 

[jedstress]

I can't recall the actual deflection but that seems very large!I agree with your statement about loads and reactions aligning up.but being a test run,and a very simple setup,I am
confused why the behaviour is so strange.the reason I was doing a test run was because one of my tasks (which I am due to start very soon) involves single shear joints.I will double check the spcs but I thought they were appropriate.I will re-assess the setup and see if the output changes.thanks for your feedback.
Rb1957,if you dont mind me asking,how long have you been in stressing?

 

[rb1957]

>20yrs, cr@p 30yrs now