interaction in bolt connection

[jfymsam86]

Hello everyone
My model has a beam=430 cm welded to extended endplate and with 8 bolt, bolted to a column=550 cm. The setting for interaction is:
Tangential, penalty, friction coeff.=0.2, hard contact.
And others are in attached file.
But each analyze interrupted after about 6 hours (about 50% of analyze) with error because of small (about 1e-5) increments and below warnings:

For contact pair (assembly__pickedsurf5625-assembly__pickedsurf5533), adjustment was specified but no node was adjusted more than the adjustment distance = 2.22000e-16.
THE SYSTEM MATRIX HAS 23 NEGATIVE EIGENVALUES. EXPLANATIONS ARE SUGGESTED AFTER THE FIRST OCCURRENCE OF THIS MESSAGE.
MATERIAL CALCULATIONS FAILED TO CONVERGE OR WERE NOT ATTEMPTED AT ONE OR MORE POINTS. CONVERGENCE IS JUDGED UNLIKELY.
Excessive distortion at a total of 77 integration points in solid (continuum) elements.
The strain increment has exceeded fifty times the strain to cause first yield at 99 points.

Thanks a lot beforehand If someone can help me.
J.fymsam

 

[jfymsam86]

Hi

what should I do for:
For contact pair (assembly__pickedsurf5625-assembly__pickedsurf5533), adjustment was specified but no node was adjusted more than the adjustment distance = 2.22000e-16.

thanks

 

[Staszkinson]

Hey,
What is the diameter of bolt hole in endplate/column flange and what is the diameter of bolt shanks?

 

[jfymsam86]

Hi
Bolt diameter is 1.25" (3.175 cm) and hole in endplate/column is 2 mm bigger than bolt diameter.
The lenght of shank is exactly equal to summation of flange and endplate thickness.

thanks for your favor

 

[Staszkinson]

That's why you got warning about contact pairs.
Try to find more information about remove overclosure option in ABAQUS help.

"Remove overclosure option" sets two parts precisely in contact at the beginning of the analysis, wnich is not possible in your case for bolt shanks(you have 2mm distance between parts).

I also recommend you to consider "tied contact pair" for bolt heads and nuts. I have seen this method in some bolted connection analysis.

 

[jfymsam86]

Hi
I tried it with tie “surface to surface”, but again stopped!
I think the most problem is in interaction between flange and endplate.
I defined: “Small sliding”, “specify distance = 0.05”, for initial.
For 1st step: “Gradually remove overclosure” and “Automatic shrink” in interference fit.
For 2nd step: “Gradually remove overclosure” and “uniform allowable> Ramp > magnitude at start= 0.0005”.
But what is this magnitude? Bigger is better or smaller? I tried with bigger and smaller figure, but again error!
Is there any setting for interactions?