nSince Displacement load is easy to converge and Interference Fit method is failing to converge, you have a way to get results.nYou are only asking why the Interference Fit method is having difficulty. I would say it has to do with the size of the interference.nI don't know exactly how the ramped effect works, Does it offset the contact element normal to each face on an element-by-element basis? If so that would bunch all the contact elements into a ball near the center of the part. That could make convergence difficult. I do know that Adjust to Touch moves the entire set of contact elements together along the vector of the maximum interference. Maybe Ramped Effects does the same, I don't know. nIn either case, only the contact element is moving, not the shell element sharing nodes with the contact element at the surface of the circle. That means huge moments are present between each contact element and its underlying shell element. This may be the reason for convergence difficulty. In the Displacement method, the contact element remains coincident with the nodes on the shell elements and no moments are present.nOne thing you can try is to flip the Contact-Target pair and see if the Ramped Effect works any better.n