Mechanical APDL Structural Analysis Guide

The tension or shear deformations within this zone are of primary interest. The surface behavior of the
material depends on the type of CZM model specified ( TB,CZM,,,,TBOPT, where TBOPT = EXPO or BILI).
Unloading behavior is not addressed in the CZM with exponential law (TB,CZM,,,,EXPO).

The surface behavior of the material is highly nonlinear in either case, and the resulting softening or
loss of stiffness changes character rapidly as the element separation increases. Unloading behavior is
not addressed in this configuration.

12.2.3.2. Material Constants -- Exponential Law

The cohesive zone model (TB,CZM,,,,EXPO) uses a traction-separation law, defined as:

n= n  t

σ − −

max∆

∆ ∆^2

for normal traction at the interface, and



= 
 +   

σ δ − − 

δ

∆ ∆ ∆

∆

for shear traction at the interface, where:

=

∂

∂

φδδ

δδ

The material constants σmax,δ^ , and δ^ are input as C1, C2, and C3.The input format is

TB,CZM,,,,

TBDATA,1,C1,C2,C3

This CZM material option must be used with interface elements INTER202,INTER203,INTER204, and
INTER205.

12.2.3.3. Material Constants -- Bilinear Law

The cohesive zone model (TB,CZM,,,,BILI) uses bilinear traction-separation laws, defined as:

= −

= −

δ

δ

λ

δ

δ

β

δ

δ

=

















+





















c





c







where

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Interface Delamination and Failure Simulation