Nonlinear Imperfect Interface

Description

This imperfect interface contact law implements an imperfect interface with tractions that depend on displacement discontinuities at the interface. The tractions must have continuous first derivative. The current implements allows only two traction laws. The material model, however, can easily be edited to create a custom imperfect interface model.

Nonlinear Interface Laws

The normal and tangential interface laws currently available listed below. This can be selected for either direction using the normal_shape or tangential_shape properties.

Linear Interface

This implementation is essentially that same as a Linear Imperfect Interface, but it is implemented without assuming a linear interface law (one use to to verify it matches more detailed solution in the Linear Imperfect Interface). Because this non-linear implementation assume continuous first derivative, however, this linear interfaces has to have the same stiffness in tension and compression (i.e., Dnt=Dnc). If you need to model a bilinear interface laws, use the Linear Imperfect Interface model instead.

Morse Potential

A Morse potential is sometimes used in molecular modeling to described bonding potential between two atoms as a function of separation distance. It is used here as an example of a reversible traction law with a peak traction. For this law, the interfacial potential energy is:

      [math]\displaystyle{ \phi_i = D_e\left(1-e^{-\alpha [u]}\right) }[/math]

where [math]\displaystyle{ D_e }[/math] is dissociation energy and [math]\displaystyle{ \alpha }[/math] controls with width of the potential well. The interfacial taction as a function of discontinuity [math]\displaystyle{ [u] }[/math] is found by differentiating energy:

      [math]\displaystyle{ T = 2\alpha D_ee^{-\alpha [u]}\left(1-e^{-\alpha [u]}\right) }[/math]

When using this potential

Properties

The properties for this law are:

Property	Description	Units	Default
normal_shape or tangential_shape	Pick which interface law to use for normal or tangential directions, respectively, by interger. Use 0 for linear law or 1 for Morse potential.	0
Dn and Dt	See Linear Imperfect interface properties. Note that this model cannot model bilinear interface and therefore one cannot set Dnt≠Dnc	pressure/length units	-1
Npeak or Tpeak	For a Morse potential, this properties pick the normal or tangential peak traction, respectively.	pressure units]]	none

Create Custom Imperfect Interface

Here

Examples

 Material "interfaceID","My Imperfect Interface","NoninearInterface"
   Dn 500
   Dt -1
   order 1
 Done