Mechanical APDL Structural Analysis Guide

12.2.2.1. Element Definition

An interface element is composed of bottom and top surfaces.Figure 205.1: INTER205 Geometry in the
Element Reference shows the geometry of a 3-D 8-node interface element. The element midplane can
be created by averaging the coordinates of node pairs from the bottoms and top surfaces of the element.
The numerical integration of the interface elements is performed in the element midplane. The Gauss
integration scheme is used for the numerical integrations.

12.2.2.2. Element Selection

The simulation of an entire assembly, consisting of the cohesive zone and the structural elements on
either side of the cohesive zone, requires that the interface elements and structural elements have the
same characteristics. When you issue the CZMESH command, the appropriate interface element(s) will
be selected automatically, depending on the adjacent structural elements. You can also manually specify
your interface elements. Use the following table as a guideline for choosing interface and structural
elements that have the same characteristics:

... use this inter- ... with one of these structural elements:

face element:

For elements with

these characterist-

ics:

2-D, linear INTER202 PLANE182

2-D, quadratic INTER203 PLANE183

3-D, quadratic INTER204 SOLID186,SOLID187

SOLID65,SOLID185,SOLSH190,SOLID272,SOLID273,

SOLID285

3-D, linear INTER205

Proper element type is chosen based on the stress states of interest and structural element types used.

Element selection is done by the element type command,ET, for example,

ET,1,205

defines element type 1 as element INTER205.

12.2.3. Material Definition

The following material-definition topics are available for modeling interface delamination with interface
elements:

12.2.3.1. Material Characteristics

12.2.3.2. Material Constants -- Exponential Law

12.2.3.3. Material Constants -- Bilinear Law

12.2.3.4. Viscous Regularization for Cohesive Cone Material (CZM)

12.2.3.1. Material Characteristics

The TB,CZM command defines interface separation behavior with interface elements. The interface is
represented by a single element set of these elements. The interface deformation is characterized by a
traction separation law (see below), with the deformation occurring only within the interface elements
(the cohesive zone).

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Modeling Interface Delamination with Interface Elements