Learning Forum

[peteroznewman]

Yes, in bonded contact, the relative position of the contact and target nodes is held fixed, if the formulation is MPC, which is my favorite. In MPC contact there is no normal stiffness, since it is a displacement constraint equation. When you change the formulation to MPC, the line items for Stiffness and Penetration disappear. If you are using Bonded Contact to join non-congruent meshes of a single part of a single material, where there is no physical bond in the part, but the solid body was sliced for meshing reasons, you don't want any change in stiffness across the interface, so there is no need to change the normal stiffness. That would be a good place to use the MPC formulation, but you don't have to because the calculation of the default normal stiffness is to use the stiffness of the materials being bonded.
Imagine you have two parts that are adhesively bonded, so there is a significant change in stiffness at the interface, but you don't want to go to the trouble of meshing that adhesive material and making a thin layer of elements to represent the adhesive. Don't you see how useful it would be to type a stiffness value into the bonded contact to represent the flexibility of the adhesive? In that case, you would not use a formulation of MPC. Use one of the other ones that allow the stiffness value to be set deliberately lower than the two materials on either side of the bond.