Learning Forum

[gcongdon]

Hi All,

I'm currently setting up/calibrating a model to represent nonlinear cyclic behavior of masonry in LS Dyna implicit. I am representing joints with *CONTACT_AUTOMATIC_SURFACE_TO_SURFACE_TIEBREAK_MORTAR_ID option.EQ.7. When I was tested the normal force-displacement behavior of the contact/masonry assembly using a displacement controlled BPM, I observed some non-physical comressive behavior with significant penetrations of the contact interface. After reviewing the manual, I started tinkering with IGAP to reduce/eliminate the penetrations. However, I am getting identical results regardless of the value I supply to IGAP. For my first run I specified IGAP.EQ.default. This was followed by values of 2 and 10. In all three cases the force and displacement are identical. I have attached a screenshot of my model, the comparative force displacement plot, and the contact definition. The SPC's only restrain the z-direction, so there shouldn't be any restraint against expansion. The BPM is z-direction only. The only connectivity between the two solid elements is the contact. The values for cards A&B are the defaults as I left those blank on the input file.

Does anyone have any suggestions of might be causing this?

[gcongdon]

After some trial and error, I've discovered that IGAP apparently does not work with TIEBREAK contacts. If I change the contact from AUTOMATIC_SURFACE_TO_SURFACE_TIEBREAK_MORTAR to a AUTOMATIC_SURFACE_TO_SURFACE_MORTAR contact IGAP does affect the contact penetration stress as documented in the manual. However, it is not clear whether this is a bug or if it is an intended behavior which is not documented in the manual.