FEA of Wrench on a Nut or Bolt

[Tools4Studs]

Has anyone ever done a COSMOS FEA of a wrench (or socket) tightening a nut or bolt?
I have been trying for a while to accurately simulate the large deformations that I have seen in person when extreme force (>3000 ft-lbf) is applied to such things as open end wrenches and sockets.
What I really need help with is how to restrain a wrench so that it can still slide on the nut a little bit while allowing the jaws of the wrench to spread.
Any input would be appreciated.
-Thanks

 

[monkeybuttons]

Your request requires an FEA program with an explicit solver to achieve a more accurate solution. An implicit solver (like the one in COSMOS) uses an analytical solution, but that is only valid for very small displacements (so small that the human eye couldn't see it without assistance). Therefore, COSMOS will not be able to accurately simulate realistic plastic deformations.

The reason implicit solvers are common place is they are considerably faster than explicit solvers, especially when the geometry is very large and complicated.

 

[rstupplebeen]

This could be solved with a nonlinear implicit solver. It could be a difficult problem due to the large deformation and potential for sliding contact.

I have not tried anything that hard with Cosmos though. I typically use Abaqus for my difficult simulations.

I hope this helps.

Rob Stupplebeen

 

[loki3000]

the problem is contact modelling and the shearing of nut corners. i think you could probably do that though. but you have to remember that nuts are not ordinary steel, they are much tougher (grade 8: 800MPa ultimate strength for example if i'm not mistaken)

 

[kellnerp]

I would say that a planar model using large deflections but not plasticity and the non-linear implicit solver in Cosmos/M might do the trick as far as getting the jaw openings on a wrench.

I would disregard the plasticity because it is generaly quite localized. You are obviously not placing either the wrench or the nut anywhere near total plastic failure.

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