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ImperfectInterface, ImperfectInterfaceMM, and Interface Commands

This command has been deprecated. You should set interfacial properties using the ContactCracks command, the ContactMM command, or a Contact material property instead.

The ImperfectInterface, ImperfectInterfaceMM, and Interface commands are used to model imperfect. When using explicit cracks, you set the default interface parameters for all cracks using:

ImperfectInterface (Dt),(Dnt),<(Dnc)>

which will automatically create and use a linear imperfect interface contact law with the provided interface parameters.

When using contact in multimaterial mode MPM to simulate imperfect interfaces, you set the default contact law to be an imperfect interface using:

ImperfectInterfaceMM (Dt),(Dnt),<(Dnc)>

where the parameters have the same meaning as for the ImperfectInterface command.

The ImperfectInterface and ImperfectInterfaceMM commands set default interface parameters for all cracks or for all material-material pairs contact, respectively. For simulations with multiple cracks, each crack can have its own interface parameters by using the (lawid) parameter in the NewCrack command (or using the deprecated CrackInterface command). For simulations with multiple materials, each material pair can choose custom imperfect interface parameters using a Contact material property within one of the materials. The deprecated method to set custom material-to-material interfacial properties was to use an Interface command within definition of one of the materials:

Interface (Dt),(Dnt),(Dnc),(matid)

where the first three parameters are same as above (except (Dnc) is required) and (matid) is the material ID for a previously defined material. This command sets contact between the material being defined and the material in (matid) to be modeled as an imperfect interface.

Notes

  1. In multimaterial mode MPM, you can combine interfaces with frictional contact be setting default parameters for friction or interface and then setting custom material-material contact rules for various pairs using Friction or Interface commands within a material definition.
  2. In theory, the interface becomes perfect in either direction as Dt or Dn approach ∞, but high values for stiffness make the problem numerically unstable (unless very small time steps are used). To make the interface perfect in any direction, set the stiffness to -1, instead of using a high stiffness. A common situation is to model the interface as perfect in compression but imperfect in tension, which is done be setting (Dntens) to any value and (Dncomp) to -1.
  3. The ImperfectInterface, ImperfectInterfaceMM, and Interface commands are only allowed for MPM analyses.