If the contact stiffness is too large, the geometric boundary condition over the contact area is exactly fulfilled, but quite often the equilibrium iteration becomes unstable. High values of contact stiffness will lead to ill–conditioning of the global stiffness matrix and result in poor convergence.

Dear Mr. Pany,

I'm afraid that I did not get your answer. However, what shall I do to solve this problem?

Regards

Pl. go through this link

http://www.algor.com/news_pub/tech_white_papers/surface_contact/