Learning Forum

[Eigil Reppe]

Hi 
I am trying to simulate forces in a steel bend restrictor, where one part is "loose" inside anotherand i keep getting this error telling me it is under constrained. 
Bend restrictor and bend restrictor clamp is bonded together, and i have added a steel plate as a section plate wich is fixed. 
and large deflection is on

i know it is probably not enough info in this post, but if anybody could help, i would be really gratefull

[peteroznewman]

Rough is an unrealistic contact model because the parts should be able to slide on each other.

What forces are acting on the structure?  Static Structural models will almost always have an internal magnitude error you see when there are "loose parts".

The best practice is to move the parts in CAD so that the surfaces that are expected to come into contact after the clearance has been taken up in the direction the force moves one part relative to the fixed part become tangent and so the Contact tool reports Closed instead of Near Open.

Using CAD to move parts to become tangent is best because there are tools such as mating or assembly constraints that can move one part to be tangent to another.  However if you don't have access to the parts in CAD, you can use the move part tool in Mechanical to type in X,Y,Z coordinates for a move.

Finally, a setting on the Frictional contact Details window is a field for Stabilization Damping Factor that provides artificial damping across the gap that allows loose parts to move and settle during the nonlinear convergence process without generating the internal magnitude error.

[Eigil Reppe]

Hi, 
Thank you so much for your answer, 

After both moving it in CAD and adding a damping factor, and making my contacts frictionless, my solution converged. 

The structure was loaded with a moment on the faces furthest away from the "wall".