*EDIT - Attached example files for which the behaviour occurs.

Hi All,

I am modifying an existing 3D Abaqus model that uses pair-wise surface-to-surface contact. The modification I am making is to combine disparate surfaces that each have their own contact pair definition into a single contact pair definition, per the example below:

The combination is achieved by re-using the existing part-level surface definitions in an assembly level surface, via combine=union, and then using only one contact pair between the assembly-level surfaces.

This is the only difference between the two models, and both models run fine with no errors. However, the midface nodes = yes option fails to trigger on the model with combined surfaces. Does anyone know why this might be happening? Has anyone else encountered this issue?

Some notes:

• The models have a cyclic symmetry boundary, in a plane parallel to the diagrams above.
• The issue occurs running in Abaqus 2020 and 2023.
• Midface nodes are required, due to the complexities of the model and necessary outputs.
• The resolution and evolution of the contact is physically accurate, there are no problems like chattering etc.